Digitally Controlled Shower, Alberto Garcia, Lorenzo Green

Transcription

EML 4905 Senior Design Project
A SENIOR DESIGN PROJECT
PREPARED IN PARTIAL FULFILLMENT OF THE
REQUIREMENT FOR THE DEGREE OF
BACHELOR OF SCIENCE
IN
MECHANICAL ENGINEERING
Digitally Controlled Shower
Final Report
Alberto Garcia
Lorenzo Green
Vladimir Louidor
Advisor: Professor Ibrahim Tansel
November 20, 2009
This report is written in partial fulfillment of the requirements in EML 4905. The
contents represent the opinion of the authors and not the Department of
Mechanical and Materials Engineering.
Team Aquemini:
[Ethics Statement and Signatures]
Fall
2009
Ethics Statement and Signatures
The work submitted in this project is solely prepared by a team consisting of Lorenzo Green,
Alberto Garcia and Vladimir Louidor and it is original. Excerpts from others’ work have been
clearly identified, their work acknowledged within the text and listed in the list of references. All
of the engineering drawings, computer programs, formulations, design work, prototype
development and testing reported in this document are also original and prepared by the same
team of students.
Lorenzo Green
Team Leader
Alberto Garcia
Team Member
Dr. Ibrahim Tansel
Faculty Advisor
2
Vladimir Louidor
Team Member
Team Aquemini:
[Table of Contents]
Fall
2009
Table of Contents
LIST OF FIGURES ........................................................................................................................ 5
LIST OF TABLES .......................................................................................................................... 8
NOMENCLATURE ....................................................................................................................... 9
1.0
Introduction ........................................................................................................................ 10
1.1
Abstract .......................................................................................................................... 10
1.2
Problem Statement ......................................................................................................... 10
1.3
Motivation ...................................................................................................................... 11
1.4
Literature Survey ............................................................................................................ 11
1.5
Discussion ...................................................................................................................... 19
2.0
Project Formulation ........................................................................................................... 21
2.1
Overview ........................................................................................................................ 21
2.2
Project Objectives .......................................................................................................... 21
2.3
Design Specifications ..................................................................................................... 22
2.4
Constraints and Other Considerations ............................................................................ 37
3.0
Design Alternatives ............................................................................................................ 39
3.1
Overview of Conceptual Designs Developed ................................................................ 39
3.2
Design Alternate 1 .......................................................................................................... 39
3.3
System Implementation Expenses.................................................................................. 44
3.4
Low Maintenance Requirements .................................................................................... 44
3.5
Precautionary Safeguards ............................................................................................... 45
3.6
Resource Conservation ................................................................................................... 45
3.7
Feasibility Assessment ................................................................................................... 46
3.8
Proposed Design ............................................................................................................. 46
3.9
Discussion ...................................................................................................................... 48
4.0
Project Management .......................................................................................................... 49
4.1
Overview ........................................................................................................................ 49
4.2
Breakdown of Work into Specific Tasks ....................................................................... 49
4.3
Organization of Work and Timeline .............................................................................. 50
3
Team Aquemini:
[Table of Contents]
Fall
2009
4.4
Breakdown of Responsibilities Among Team Members ............................................... 51
4.5
Commercialization of the Final Product ........................................................................ 51
4.6
Discussion ...................................................................................................................... 52
5.0
Engineering Design and Analysis ...................................................................................... 54
5.1
Shaft Adapter Design Analysis ...................................................................................... 54
5.2
Heat Transfer Analysis ................................................................................................... 56
5.3
Component Design Analysis .......................................................................................... 65
6.0
Prototype Construction ...................................................................................................... 68
6.1
Description of Prototype ................................................................................................ 68
6.2
Prototype Design ............................................................................................................ 72
6.3
Prototype Components ................................................................................................... 73
6.4
Programming of Prototype ............................................................................................. 90
6.5
Prototype Cost Analysis ................................................................................................. 97
7.0
Testing and Evaluation ...................................................................................................... 99
7.1
Overview ........................................................................................................................ 99
7.2
Design of Experiments - Description of Experiments ................................................. 100
7.3
Test Results and Data ................................................................................................... 102
8.0
Design Considerations ..................................................................................................... 106
8.1
Assembly and Disassembly.......................................................................................... 106
8.2
Regular Maintenance of the System............................................................................. 112
8.3
Major Maintenance of the System ............................................................................... 112
8.4
Environmental Impact .................................................................................................. 114
8.5
Risk Assessment........................................................................................................... 114
9.0
Conclusion ....................................................................................................................... 116
9.1
Conclusion and Discussion .......................................................................................... 116
9.2
Patent/Copyright Application....................................................................................... 120
9.3
Commercialization Prospects of the Product ............................................................... 120
9.4
Future Work ................................................................................................................. 121
10.0 References ........................................................................................................................ 123
4
Team Aquemini:
[List of Figures]
Fall
2009
LIST OF FIGURES
Figure 1: Y Shaped Ge-Doped
Figure 2: Stepper Motor Winding
Figure 3: Stepper Motor Winding w/Poles
Figure 4: Stepper Motor Winding w/H Bridge
Figure 5: Moen ioDigital Shower
Figure 6: Kohler Digital Interface
Figure 7: Selected Motor Model 42BYG205
Figure 8: Dimensions Of The Motor (All units are in mm)
Figure 9: Board of Education
Figure 10: Bistep2A Serial Board
Figure 11: BS2 Board of Education connected to a BiStep2A Microcontroller
Figure 12: QTI sensor
Figure 13: QTI Sensor Circuit
Figure 14: LM 34 Temperature Sensor
Figure 15: 8 Bit A\D Converter
Figure 16: 2x16 Backlit LCD
Figure 17: CO2 Canister
Figure 18: Air Regulator
Figure 19: Pressure Gauge
Figure 20: Solid Outline of Shaft Adapter
Figure 21: Modified Shaft Adapter Drawing
Figure 22: Flared JIC
Figure 23: Flared SAE
Figure 24: NPT to Male JIC Fitting
Figure 25: Push on Barb Fittings
Figure 26: Pressure Tank Assembly
Figure 27: Machined Lid
Figure 28: Installed Fitting on Tank Lid
Figure 29: Machined Outlet Nozzle
Figure 30: Installed Fitting on Tank Nozzle
Figure 31: Bulkhead Fitting
Figure 32: System Comparison
Figure 33: Needle Valve Detail
Figure 34: Needle Valves
Figure 35: Calibration Tank
Figure 36: Conceptual Valve Control Setup
Figure 37: User Interface Display Panel
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Team Aquemini:
[List of Figures]
Figure 38: Example of Mixer Valve
Figure 39: Stress Analysis for an Aluminum Key
Figure 40: Stress Analysis for a Carbon Steel Key
Figure 41: Thermal Conductivity of Common Materials
Figure 42: Three Heat Transfer Modes
Figure 43: Example Mixing Chamber
Figure 44: Displacement Analysis Results
Figure 45: Stress Analysis
Figure 46: Pressure Regulator with Mounted Fittings
Figure 47: Grainger Industrial Supply Catalogue Pg.3308
Figure 48: Preventing Leaks Using Sealants
Figure 49: Hose Assembly
Figure 50: Constructed Prototype Design
Figure 51: Sample LCD Testing Program
Figure 52: Temp Readout on LCD w/Temp Sensor
Figure 53: Board of Education
Figure 54: Motor Winding Resistance
Figure 55: Project Power Supply
Figure 56: Wiring Diagram
Figure 57: Clamped Hose Assembly
Figure 58: Water Hose Assembly Process with Swivel Fitting
Figure 59: Water Hose Assembly Process with Clamped Fitting
Figure 60: Final Water Hose Assembly
Figure 61: Heating Element
Figure 62: Motor with Shaft Adapter
Figure 63: Temperature Control Valve
Figure 64: Flow Control Valve
Figure 65: Thermal/ Fluid System Diagram
Figure 66: Sample BS2 Script
Figure 67: Sample BS2 Script cont
Figure 68: Motor Control Using QTI Sensor
Figure 69: Temperature vs. Position Analysis
Figure 70: Front Panel Construction
Figure 71: Machining Wood Beams
Figure 72: Complete Motor and Valve Assembly
Figure 73: Semi-Constructed Display Stand
Figure 74 : Fixed Motor on Mixing Valve
Figure 75 : Motor and Valve Support Assembly
Figure 76 : Assembled Electrical Compartment
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Team Aquemini:
[List of Figures]
Figure 77 : Electrical Components in Compartment
Figure 78 : Complete Prototype Assembly
Figure 79: Pneumatic and Hydraulic System Assembly
Figure 80 : Behind the Prototype
Figure 81: Digitally Controlled Shower
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Team Aquemini:
[List of Tables]
Fall
2009
LIST OF TABLES
Table 1: Comparative Shower Features ........................................................................................ 19
Table 2: Component List .............................................................................................................. 22
Table 3: Timeline of Project ......................................................................................................... 50
Table 4: Data and Results of Pressure Analysis on Water Tanks ................................................. 66
Table 5: Current Multipliers ......................................................................................................... 80
Table 6: Controller Boards............................................................................................................ 81
Table 7: Component List .............................................................................................................. 98
Table 8: Temperature Trial Analysis .......................................................................................... 103
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Team Aquemini:
[Nomenclature]
NOMENCLATURE
Symbol
t
T(t)
Ta
h
c
AS
V
D
L
H
k
Nu
P
∆P
Pr
Q
Re
μ
v
∆h
ρwater
Ρair
g
Ts
Description
Time
Temperature at Time t
Ambient Air Temperature
Convection Heat Transfer Coefficient
Heat Capacity
Surface Area
Volume
Diameter of the Rod = 0.0949
Length of the Rod = 0.0125
Liquid Pressure Head
Thermal Conductivity
Nusselt Number
Pressure
Differential Pressure
Prandlt Number
Rate of Heat Transfer
Reynolds Number
Viscosity
Air speed
Pressure Read from Manometer
Density of Water
Density of Air
Acceleration due to Gravity
Surface Temperature
SI Unit
s
K
K
W / (m2·K)
J / (kg·K)
m2
m3
m
m
m–H2O
W/(m·K)
n/a
Pa
Pa
n/a
W
n/a
kg/(m·s)
m/s
in-H2O
kg / m3
kg / m3
m/s2
K
Ta
Ambient Air Temperature
K
Ts
Surface Temperature of Cylinder
K
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Fall
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Team Aquemini:
1.0
Introduction
1.1
Abstract
[Introduction]
Fall
2009
Year after year new products are introduced in the technological market from home appliances to
personal gadgets.
The advancement of technology is rapidly changing the landscape of
consumer consumption with more and more humans becoming heavily dependent on them.
Technical efficiency is becoming more sophisticated and every product promises more advanced
features that would heighten the user experience. Computer technology has become so integrated
in the general population over the years that many have become dependent on them to make lives
easier. They have found a place in homes and daily lives; from computers and laptops to the
TiVo and the BlackBerry. Recent technical developments in the past decade have seen the
introduction of the rumba, a robotic platform that autonomously vacuums your home floor, a
self-cleaning toilet along with many more innovations that have infiltrated homes.
More
breakthroughs have yet to hit the market that would significantly increase user productivity in
and outside of the home.
1.2
Problem Statement
Having surveyed the different types of digitally controlled shower systems available from all
vendors, one identifiable problem that became persistent and common in these systems was that
what they were marketing were highly expensive and did not include the cost of installation or
materials. The goal of this project is to develop a similar system that delivers the same basic
functions at a lower cost in purchasing, installation, and maintenance of the system. The system
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Team Aquemini:
[Introduction]
Fall
2009
will be designed to incorporate simplicity through functionality, and most importantly cost
effectiveness.
1.3
Motivation
The group’s primary motivation for considering this project is the idea of delivering a cost
effective digitally controlled shower kit that gives the user control over flow intensity and
temperature settings for easy access. The motivation stems from the positive impression the
group received from an already existing product that was available in the market, but after
further research into the cost of such a system it was deemed too expensive for the average
household to afford. The cost of the system did not include the cost of installation, which would
add high labor and material cost (to rebuild the walls that would have to be knocked out). Such a
system that would require routine maintenance can only be purchased by those with higher
incomes. The implementation of the group’s project would eliminate high costs in both
installation and maintenance costs.
1.4
Literature Survey
This survey will discuss at length the core components of the group’s shower system including
advancements that have made that can better approve the quality and performance of the system.
One of the system’s components that is integral to the system’s overall performance is the use of
Parallax’s LM34 Temperature Sensor [1]. The sensor itself is suitable for the application that the
group is employing its use for, but extensive research into obtaining temperature readings
through the use of fiber optics has been in development for a number of decades. Methods such
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Team Aquemini:
[Introduction]
Fall
2009
as optical-scattering, fluorescence, and optical absorption have all been thoroughly explored as
alternatives to standard temperature sensing devices [10]. One particular method that has stood
out is the use of In-Fiber Bragg Gratings (FBR). FBR is an optic fiber that reflects a particular
wavelength that is satisfied by the Bragg condition
[15]. FBG is
widely regarded favorably over its competitors due to the robustness of the wavelength
codification, its small size and low cost [13]. The temperature sensitivity reaches approximately
13pm/°C, employing the use of different materials such as polymers or using long period
gratings as coating the sensitivity of FBG can increase significantly from 108 pm/°C to 310
pm/°C respectively [10,11]. Extensive research was performed to investigate the price of a
digital shower system, as well as the availability of current digital shower systems on the market.
Many factors come into play when selecting such an advanced system. A typical shower
assembly has one outlet nozzle head for the shower, one outlet nozzle head for the tub, and two
control knobs for selecting hot and cold water. On a more advanced analog system, the options
for the shower nozzle can be as many as one to six heads, all positioned in various directions.
Once this analog system becomes digital, all of the options for shower nozzle heads must be
factored into the programming of the system. The optimization of the digital shower system to
recognize and control all of the shower nozzle heads, as well as incorporate hot and cold water
mixing preferences plays a crucial role in determining the final price of the system.
What the authors of several journals are proposing is using fiber optics particularly photonic
crystal fibers that have Germanium-Doped (Ge-Doped) cores that would produce a wavelength
encoded temperature sensor using the temperature dependence of the cutoff wavelength
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Team Aquemini:
[Introduction]
Fall
2009
characteristic found in a liquid filled germanium doped microstructure fiber [12] to create a
temperature sensor device.
The properties of using Ge-Doped core are appealing because of the following traits [8]:
Low Loss splicing to standard fibers
Using conventional techniques to ease the use of photo inscription of fiber gratings
Good guidance when the holes are collapsed to build in-fiber gas or liquid cells
Figure 1: Y Shaped Ge-Doped [10]
Figure 1 is a Y shaped Ge-doped core that the authors used in their experiments, three
passageways can be observed in the figure, and such passageways would make it easy to fill
them with liquid. The liquids used throughout their experiments have a nominal refractive index
(RI) value of 1.46, and 1.48, measured at 589 nm and 25°C [8].
The temperature coefficient of these liquids is approximately
. Hence when one
fiber is filled with any of these liquids, the cutoff of the fundamental mode takes place at a given
wavelength, as a function of the refractive index value [8]. The results obtained from the authors’
experimentation into the use of photonic crystal fiber optics yielded very promising results. The
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Team Aquemini:
[Introduction]
Fall
2009
sensitivity is mainly determined by the thermo-optic coefficient of the liquids that fill the fibers.
An estimated sensitivity of 25 nm/°C has been observed with a detection limit of roughly
0.001°C [8].
The use of fiber sensors are very promising in the field of improving the accuracy of temperature
sensing and can serve a beneficial role in the shower system. The LM34 temperature sensor has
an accuracy of 1°F that is guaranteed at +77°F, while the author’s experiment yielded a detection
limit of 0.001 . Such precision can be used to provide the user with an ever increasing control
of the temperature of the water. The user can accurately change the temperature without
worrying about burning himself with scalding hot water. Of course other constraints such as the
cost of fabricating these fiber sensors relative to the cost of a single LM34 temperature sensor
would have to be carefully looked at and discussed, the benefits in a particular application must
outweigh the cost of implementing fiber sensors. Despite the opportunity in utilizing new
technology in the field of temperature sensors, the LM34 sensor suits the basic functions and
needs of the group’s digital shower system.
The use of a stepper motor for the group’s application came in the form of a recommendation.
For the particular use of controlling the flow of water and temperature settings the system would
require a motor that provided precision. This section of the survey will discuss the different types
of stepping motors that are available, their characteristics and uses.
Stepping motors come in two forms; permanent magnet or variable reluctance motors permanent
magnet motors tend to feel like a bumpy road as you twist the shaft of the motor around, while
the shaft of the variable reluctance motor have a propensity to spin freely[ 7].
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Team Aquemini:
[Introduction]
Fall
2009
Variable reluctance motors usually come with three windings all connected to a common
terminal, that when put to use in an application the common terminal is connected to the positive
supply while each winding is energized in sequence as seen in Figure 2.
Figure 2: Stepper Motor Winding [6]
Unipolar motors are of the permanent magnet variety and often come with 5 to 6 leads that are
typically wired with center nodes 1 and 2 connected to each of the two windings while the ends
A and B are connected to ground in order to reverse the direction of the magnetic field of that
particular winding similar to Figure 3.
Figure 3: Stepper Motor Winding w/Poles [6]
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Team Aquemini:
[Introduction]
Fall
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Winding number 1 is coiled between the top and bottom poles, creating the north and south
poles. For the second winding it is then coiled around the left and right motor poles. This
arrangement allows the creation of a permanent magnet with 6 poles, 3 South and 3 North
located around its circumference [7]. Motors that come in higher angle resolutions of 1.8 to 15
degrees per step have to develop proportionally more poles.
Bipolar Motors are built in a similar fashion as unipolar motors, except the two windings are
wired in such a simpler method that center nodes are not used as shown in Figure 4.
Unfortunately the drive circuitry is more complex if the user wishes to reverse the polarity of the
poles. To solve such issues an H-bridge is used. H-bridge connections allow the polarity of the
power source applied to each end of each winding to be controlled independently [7].
Figure 4: Stepper Motor Winding w/H Bridge [6]
Given the various types of stepper motors available the unipolar motor seems best suited for this
application. One of the reason the group chose an unipolar motor above all else, was the wiring
configuration was simple and provided the possibility to reverse the polarity of the magnetic
field, while the bipolar motor did not offer a simple system as easily and required an H-bridge
16
Team Aquemini:
[Introduction]
Fall
2009
connection to be used. This particular motor also provided a resolution of 1.8 degree per step
which would give the group more accurate control of the shaft position of the motor. Other
parameters that contributed to the team’s decision were the required torque to actuate the valve
in of the mixing valve. The group also wanted to find a motor that was affordable that would be
able to meet the other criteria, fortunately the motor chosen fits the objectives of this project.
For simplification purposes, the design will be based on the principle that there will be only one
outlet water shower nozzle head, one cold water input, and one hot water input. A comparative
consumer product available today is the Moen ioDIGITAL Shower and the Kohler K-686-1
DTV II Primary Digital Interface.
Figure 5: Moen ioDigital Shower [18]
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Team Aquemini:
[Introduction]
Fall
2009
Figure 6: Kohler Digital Interface [17]
It is important to note the various differences and similarities between the design project being
constructed, the Moen ioDIGITAL Shower and the Kohler K-686-1 DTV II Primary Digital
Interface. These differences will serve to increase the marketability, and ultimately the base
price of the shower control interface device. The greater the functionality of the control interface,
the greater the asking price for the device can be. A control device that can only control one
shower head nozzle, and does not support the adaptability to control more than one device will
cost significantly less than other control devices. In addition, a control device that does not
provide a digital, numerical readout of the current water temperature will also cost less. The cost
of the product will ultimately be based upon the amount of features the control device has and
the adaptability of the device to the current shower system.
For the design droject, the Moen ioDIGITAL Shower and the Kohler K-686-1 DTV II Primary
Digital Interface, there are many differences to be noted that will vary the price of the operating
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Team Aquemini:
[Introduction]
Fall
2009
control unit significantly. A digital display of the current settings of the system is available for
the Team Aquemini Design Project and the Kohler K-686-1 DTV II Primary Digital Interface.
The digital display is important because it gives a more user friendly operation for the device. As
an added accessory, Moen ioDIGITAL Shower has a remote that allows the user to control its
features from outside of the shower; a useful feature for those who seek it. All three digital
shower designs provide the user to actively adjust the temperature of the shower. A massage
control function is only available with the Kohler device. However, an output pressure flow
control option is available on all models except for the Kohler control device. The only device to
not have programmable user presets is the Team Aquemini device.
Table 1: Comparative Shower Features
1.5
Discussion
Approaching this design will be moderately difficult; having decided that such a system can be
implemented quite easily since the basic frame work of the piping system for the shower design
already exists. The group has discussed packaging the system as a kit, which will include the
motors that control the flow and temperature of the water. The user interface would be digitally
controlled, replacing all knobs and handles usually included in a shower system. This digital
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Team Aquemini:
[Introduction]
Fall
2009
interface will be water proof to prevent electrical incidents. Implementing such a product for full
commercial use would require more foresight into the needs of the individual, for instance in the
conceptualized commercial design of the system, a lithium ion batteries can be used as a power
source or for environmentally conscious individuals the use of a solar panel to power the system
can be an extra incentive.
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Team Aquemini:
2.0
Project Formulation
2.1
Overview
[Project Formulation]
Fall
2009
Over the course of the project several ideas have been developed to be implemented in the design
of the system; from selecting the motors, motor microcontrollers, hoses, fittings and various
other equipment and implementing them to the overall design of the prototype. Several times has
the group switched back and forth over the final design of the system and how it will be
implemented. Over the course of the summer the group developed honed in on two ideas; one,
developing the original design of replacing the current analog showers that are in today’s home
market with a cost effective, simple digital interface system, that is significantly cheaper than
what is currently available in the market or develop a portable digital shower system and
simplifying the number of parts needed for development. The latter was based on the concept of
conducting outdoor activities such as camping or hiking as an alternative to purchasing an RV
for such activities. Although this design project is focusing on one design, if the group were to
operate as a real business the second alternative can lead to an expansion of the system and
business. As of September 4, 2009 the group has decided to develop the original idea of simply
replacing the analog controls found in regular showers with a digital system that provides the
user with an overall affordable system.
2.2
Project Objectives
The objective of this project is to design a fully digital shower system at a cost effective rate and
provide simple functionality. Surveying several different vendors the group found that such
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Team Aquemini:
Fall
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systems were extremely overpriced, even for core pieces of the system such as the user interface
were expensive. The systems that are commercially available did not include the installation fees
or plumbing costs that the system would incur. With the system the team has developed and
designed, a less expensive system can be used that delivers the same basic functions as the
products that are out in the market today and can be installed at a lower price. Simplicity,
functionality and affordability in the design will be vital to achieving the main objectives.
2.3
Design Specifications
The construction of the prototype will involve a range of components from electrical circuits to
pneumatic systems, to be employed by this design project. Below is a prepared list of all the
components that had been collected early in the design process for experimentation.
Table 2: Component List
Component List
Board of education with Basic Stamp 2 module
Bistep 2A microcontroller
2 Jameco Motor Model # 42BYG205
1 QTI sensor
A 2 by16 Backlight Liquid Crystal Display
1 Mixer Valve
1 Analog to Digital 0831 converter
1 LM34 Temperature Sensor
1 Air Regulator
1 Pressure Gauge
1 CO2 Canister
2 1 gallon tanks
1 Heating element
1 Valve
3 QTI sensors
10 feet long Tubing
Fittings
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The parameters for selecting the stepper motors were: it had to provide precise control over the
flow and temperature settings of the water, the motor had to produce enough torque to actuate
the handle of the mixer valve. Figures 7 and 8 respectively, are the motors the prototype will be
utilizing along with its specifications and dimensional design. This particular motor was chosen
because it was a cost effective motor that provided more than enough torque to actuate the mixer
valve. The torque rating is 1300 g-cm (18.33 in-oz), the measured torque that would be required
to turn the pin valve is at most 16 in-oz or less.
Figure 7: Selected Motor Model 42BYG205 [18]
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2009
Figure 8: Dimensions Of The Motor (All units are in mm)[18]
For the electrical aspect of the design project, several components were selected due to various
elements such as ease of use, a user friendly design and programming requirements, and low
cost.
The Parallax Basic Stamp 2 module is a microcontroller that is able to control and monitor
timers, keypads, motors, sensors, switches, relays, lights, and more. The module is
programmable through a simple language called PBasic and was chosen because of knowledge
of the programming language learned in previous engineering courses. After conducting
extensive research, a stepper motor controller board compatible with the Board of Education
(BOE) was found. The secondary BiStep2A microcontroller pictured in Figures 9 and 10
respectively will be implemented and work in conjunction with the BOE. The Bistep2A
microcontroller allows the system to regulate the power and control of up to two stepper motors
while acquiring a power source that would meet the power requirements of the system. The two
motors can be independently controlled, which fits the system’s needs by allowing to configure
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Team Aquemini:
Fall
2009
the programming for both the temperature and flow intensity settings, one motor for each
operation. By finding the right motor that produces the torque needed, the amount of power that
would be required to run the system and actuate the mixing valve can be finalized.
Figure 9: Board of Education [19]
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Team Aquemini:
Figure 10: Bistep2A Serial Board [20]
Figure 11: BS2 Board of Education connected to a BiStep2A Microcontroller[20]
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Team Aquemini:
Fall
2009
Figure 11 is a photograph of a circuit showing how the stepper motors will be controlled and
regulated by the Board of Education and the BiStep2A microcontroller. In this example only one
power supply is being used, for experimentation purposes two separate power supplies will be
used and a common ground will be established. To prevent ground and wiring issues one power
supply would be used once the prototype has been finalized. Even though in the photo there is an
incomplete circuit of the Board of Education the basic setup remains the same.
Receiver
Transmitter
Figure 12: QTI sensor [6]
As for the user interaction with the interface, the original idea was to implement the use of
buttons to control the flow and temperature settings of the water system. Upon further
consideration the team decided to upscale the interface into implementing QTI sensors, seen in
Figure 12. These are basically infrared sensors that use black and white surfaces to operate at
different voltages. When the IR LED’s signal is absorbed by a black surface, the voltage R goes
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Team Aquemini:
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2009
above 1.4 volts, the basic stamp interprets any voltage above 1.4 as 1, below will be 0. So
implementation will be that of using the sensors to replace the functions of a button. Instead of
pushing a button, the user will simply place his/her hand or finger in front of the QTI sensor, the
sensor will be read as 1 and the temperature or flow will increase/decrease, removing his/her
hand will send a signal of 0, stopping the operation. Four of these sensors will be employed for
the increase/decrease operations of the temperature and flow intensity.
Figure 13: QTI Sensor Circuit [6]
The next two components work together to measure the temperature of the environment and
convert that temperature from an analog to a digital display on its screen. The temperature sensor
measures each degree with a 10mV measurement, one degree equals 0.01 V. The 8 bit A/D
Converter takes this voltage measurement and sends an out-put as a digital signal that is read in
Fahrenheit or Celsius, depending on how the programmer want to set the temperature unit.
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Team Aquemini:
Figure 14: LM 34 Temperature Sensor[1]
Fall
2009
Figure 15: 8 Bit A\D Converter [21]
The temperature display component consists of a 2 by 16 backlit liquid crystal display (LCD).
This particular display was chosen because it would allow the team and user to display both the
temperature and flow intensity settings to the user and that it is cheaper than other similar
products. The temperature can be displayed at the top in the first row, while the flow intensity
can be displayed in the second row.
Figure 16: 2x16 Backlit LCD [22]
Another concept the group has developed is creating an environment to control the pressure that
would deliver the water throughout the shower system. The idea was to use a CO2 canister, to
pressurize two tanks, one for hot water the other for cold, just like a conventional water pipe
system in a home where water is pressurized upon delivery. Such a system would help the team
in regulating the flow intensity of the fluid traveling through the system. In order for the group
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2009
to safely harness the air supply, an air regulator, shown in Figure 18 along with a pressure gauge,
Figure 19 would be used. The air regulator and pressure gauge allows the system to cut off the
flow of gas at a specific pressure. An air regulator consists of three elements; a loading element,
a measuring element, and a restricting element.
A Restricting Element: This element is a type of valve arrangement; it can be a globe valve,
butterfly valve, poppet valve, or any other type of valve that is capable of operating as a variable
restriction to the flow.
Loading Element: This element is what applies the needed force to the restricting element. This
can be any number of things such as a weight, a spring, a piston actuator, or more commonly the
diaphragm actuator in combination with a spring.
Measuring Element: This element indicates when the inlet flow is equal to the outlet flow. The
diaphragm is widely used because not only is it used for measuring but as well for loading
purposes.
Figure 19: Pressure Gauge [25]
Figure 18: Air Regulator [24]
Figure 17: CO2 Canister [23]
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Team Aquemini:
Fall
2009
Figure 20: Solid Outline of Shaft Adapter
The final shaft adapter design, used to couple the stepper motor shaft to the valve knobs, was
modified for precautionary measures to make sure the adapter was fitted tightly around the valve
pin to prevent any slipping that may occur. Instead of implementing one set screw, it was
decided on using four set screws by recommendation of the manufacturing laboratory professor.
The initial design can be seen in Figure 20 and the final design in 21.
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Team Aquemini:
Figure 21: Modified Shaft Adapter Drawing
32
Fall
2009
Team Aquemini:
Fall
2009
Fitting selections for the assembly of the prototype has required thorough research and various
trips to suppliers. Before any materials were purchased for the fluid delivery system, it was
desirable to make sure the required pressure and flow would be achieved with the materials
obtained. After applying the flow equation, q = av and the Bernoulli equation,
the amount of water that would be output
depending on the diameter of the hose and the pressure being applied to the tank was calculated.
Knowing this, the group decided to use a ½” inner diameter hose for water flow and ¼” hose for
the pressure lines. Since this system is going to be operated at low pressure, the group could
afford to purchase low pressure rubber and transparent vinyl hoses which were inexpensive and
practical.
After choosing the size of the air and water lines, the group had to choose what type of
connection, out of many, for the joints to have. After researching flared fittings, the group found
that the seats are manufactured at two different angles, 37 and 45 . The seat is the angle at
which the mate is machined, the male and female fitting must share the same seat angle in order
for the two surfaces mate and seal properly. The group chose to work with 37 fittings.
Figure 22: Flared JIC [26]
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Team Aquemini:
Fall
2009
Figure 23: Flared SAE [27]
The fluid schematic of the system is as follows: A pressurized CO2 tank is has an adapter with a
1/8” NPT female connection. The group used a nipple to connect the adapter to the pressure
regulator which also has a 1/8” NPT female. A pressure gauge was attached to the regulator in
order to read how much pressure was being supplied to the system, the group plans to pressurize
the tanks to about 5 psi. Coming out of the other end of the air regulator, a NPT to Flared fitting,
which connects to the hose is attached. The group utilized the one pressurized CO2 tank
connected in series to supply the pressure at both tanks but soon found that the CO2 tank only
allowed for a few trials before depleting. The group then chose to work with the compressed air
supplied at the student machine shop to conduct future test. Since the tanks are the same size and
contain equal amounts of water, the pressure one tank will see is equivalent to the pressure the
other tank sees.
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Team Aquemini:
Figure 24: NPT to Male JIC Fitting [29]
Fall
2009
Figure 25: Push on Barb Fittings [30]
Hoses were then used to connect the pneumatic system components. Using push on barb fittings
the group made hose assemblies that would supply pressure to the water tanks and provide the
energy to transport the water from one place to another.
1/8” Nipple
Pressure Regulator
1/8” Male NPT
To
1/4” Male JIC
Tank Connection
Adapter
Pressure Gauge
CO2 Tank
Figure 26: Pressure Tank Assembly
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Fall
2009
In order to connect the hoses to the tanks, it was necessary to machine the tank lids and install
bulkhead fittings. Sealant will be applied in order to prevent any air leaks which cause loss of
pressure.
Figure 28: Installed Fitting on Tank Lid
Figure 27: Machined Lid
The same sealing method is used to provide the water an outlet without leaking, using a larger
size bulkhead fitting the group connected a transparent vinyl hose to the valve input to supply the
hot and cold water to their respective valves.
Figure 29: Machined Outlet Nozzle
Figure 30: Installed Fitting on Tank Nozzle
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Fall
2009
Figure 31: Bulkhead Fitting [31]
The group chose a bulkhead style fitting because it provided the opportunity to install the fitting
on the water tanks without having to tap whole and thread the fitting in. With the bulk head the
group was able to slide the fitting into the orifice and tighten the connection with a nut which
presses against the inside of the tank, as seen in Figure 30. Using this type of fitting along with a
sealant that fills any open spaces, the pneumatic/ hydraulic system would have minimum energy
loss.
2.4
Constraints and Other Considerations
At the moment the constraints selected for the design is for it to be compact, easy to set up and
affordable. Originally the group planned to design a system to replace the analog shower with a
digital version as provided by other makers. An early example of the original design used the
process of reverse engineering and designing the idea around the traditional shower plumbing
configuration. Figure 32 shows how the old design would’ve been implemented into the
traditional setup.
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Team Aquemini:
Fall
2009
Figure 32: System Comparison
In addition, the group has decided to take into account other deciding factors into the approach of
designing such system that will help understand the constraints and the approach of marketing
the final product. These factors are representative of the various needs and wants of the end user
of this prototype, the general public. The group has determined that the direction for the design
of the prototype will be, in turn, be guided by these factors to ensure the successful marketability
and prototype operation. The group has determined these factors by researching a needs
assessment of the general public with respect to portability and cost. The design of the prototype
will be based upon the following; Adaptability, Low Initial Modification Expanse, Low
Maintenance Requirements, Precautionary Safeguards, and Resource Conservation.
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Team Aquemini:
[Design Alternatives]
3.0
Design Alternatives
3.1
Overview of Conceptual Designs Developed
Fall
2009
As the project progressed throughout the semester, the group has undergone several design
changes, some changes were made for aesthetic reasons others were based on component
selection, the group has made numerous changes switching back and forth over the final design
of the system and how the components will be implemented. After dropping the portable shower
idea as an option for campers, the compact design was still maintained and applied to
conventional shower systems. Deciding what types of valves to use, what size fittings, what
length hoses was discussed at length between group members and a consensus was reached. The
final prototype design would consist of a mixing valve in line with a garden hose valve to control
flow, stepper motors would be coupled to the valve knobs to provide control via sensors. A
quarter inch rubber hose was to be used to compress the water tanks and fittings selection would
be restricted to a minimum amount that would provide easy positions for the hoses and other
components to meet.
3.2
Design Alternate 1
At the initial stage of the project, the materials needed to realize such a system was being
collected. Group discussions have taken place to discuss at length which valves would best suit
the needs of the design when it comes to controlling the water flow. Ball valves, cock valves and
needle valves are the three options that have been chosen. The group has decided that Needle
valves, shown in figure1, would better suit the design requirements, given they provide the user
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Team Aquemini:
Fall
2009
better control of the water flow throughout the system, allowing the user better flow precision.
Needle valves are generally more cost effective then the other two options allowing the final
product to be more affordable for the consumer.
Figure 33: Needle Valve Detail [8]
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Team Aquemini:
Fall
2009
Figure 34: Needle Valves [32]
To achieve the preferred temperature, careful calibration will be carried out using a calibration
tank as seen in Figure 35. Using trial and error, insertion of a temperature sensor into a
calibration tank would be used to read the temperature values for the different settings of valve
openings. For instance, when the hot water valve is half opened and the cold water is fully
opened that mixture of water will go into the calibration tank and it will be said that for those
valve settings there is a corresponding output temperature. These readings will be recorded and
programmed into the control panel.
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Team Aquemini:
Fall
2009
Figure 35: Calibration Tank
Implementation of the stepper motors in actuating the needle valves, will involve designing a
shaft adapter. One end of the adapter will consist of an orifice where the shaft of the motor can
be inserted. The other end of the adapter will consist of two protruded rods that will be inserted
into two circular holes in the T-shaped handle. Each step the motor turns the adapter will actuate
and turn the handle. An early concept of the how the group planned to couple the valve and
motor is presented in Figure 36.
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Fall
2009
Figure 36: Conceptual Valve Control Setup
Figure 37: User Interface Display Panel
Figure 37 is the concept for the system’s user interface panel. One can observe the design
includes several displays that reveal the temperature, pressure flow, and the time. Just below
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2009
those LCD displays are the analog controllers (i.e., buttons) for the system, each set of buttons
corresponds to an operation. During the early stages of development, the original idea did not
include the implementation of the shower and bath activation features. The idea was later
included enhance one of the group’s objective of simplicity through functionality.
3.3
System Implementation Expenses
It was of great importance to the group to design a product that could be integrated into an
existing home plumbing system with minimal cost. As a result of achieving seamless adaptability
for the new prototype into the pre-existing plumbing system, high modification expenses can
accrue. Sources of possible expenses can include the type of motorized ball valve, the type of
check valve and the type of directional flow control valves used. Expenses can incur when the
components that are selected have unnecessary additional features. For example, it was
determined that the pressure that the components will experience is in the range of 30 psi. It
would be unnecessary for the group to select valves that are capable of operating under
conditions of 300-500psi. This would be a costly and unnecessary design alternative. Also, the
group has also determined that the operating temperature for the prototype will range from 45°F
to 85°F. Once again, it would be a costly and unnecessary design alternative to select
components that are capable of operating in temperature ranges that are significantly greater than
what is anticipated. Selecting the correct components for the prototype will ensure that initial
modification expenses will be kept at a minimum.
3.4
Low Maintenance Requirements
Another one of the design concerns of the group was to ensure that once a prototype was
eventually marketed to consumers, that product could be easily maintained without using any
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Fall
2009
special equipment or having to use a specialist mechanic. A way to ensure this was to select
components for the product that were not especially made, therefore only required current
knowledge to perform work on. Due to a design selection of everyday, known components,
maintenance costs were kept at a minimum.
3.5
Precautionary Safeguards
One of the design features of the digital shower interface system is the ability for the customer to
see the real time temperature of the water on a seven segment liquid crystal display (LCD) that is
positioned on the digital shower interface display. This design of the prototype serves as the
precautionary safety safeguard measurement. With this LCD display, the temperature of the
water can be determined in a manner that will pose no harm to the costumer. Currently, the way
in which one will measure the temperature of shower water is by gauging it by touch. This
method of checking the temperature of the water can prove have a safety risk. If the water is
extremely hot, and the customer unknowingly makes contact with the water, the water can
potentially scold the customer.
3.6
Resource Conservation
Finally, the prototype places an emphasis on resource conservation. Based upon research, at
60psi, the average shower head will deliver approximately two gallons per minute. To save on
unnecessary water waste, the digitally controlled shower has been designed to have the capability
to significantly decrease the flow of water at times when the customer deems necessary. All the
customer must do is press a single button and the water delivery will decrease from two gallons
per minute to approximately one and a half gallons per minute. The prototype is designed so that
it will not delivered water at 60 psi but at 5 psi.
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Team Aquemini:
3.7
Fall
2009
Feasibility Assessment
After completing the literature survey and discussing at length the parts needed and the design
aspects of the system, the group adamantly believes that the concept is fully feasible. Given the
revisions to the original concept design and elimination of all hurdles that the calibration test
would have given. Measuring the temperature of the water and pinpointing the position of the
shaft at the exact moment of the current water temperature would’ve been time consuming and
could potentially contain many errors that would have resulted in poor performance of the
system. Such arduous tasks can be trouble for the programming portion of the prototype since the
shaft position will have to be pre-set and with whatever temperature the user chooses the shaft
will actuate the valve until the position that correlates with that temperature is reached. In
dealing with this design aspect the group took an easier and much more viable route by giving
the user full control over the system, instead of using preset temperature-shaft positions. The
user will simply choose to increase or decrease the flow and temperature operations.
3.8
Proposed Design
Re-examining the design of the system and taking into consideration the cost of building the
prototype and the goal of a simplified digital shower system the group has decided to discard the
use of needle valves and replace it with a mixing valve. A mixing valve is the perfect component
for the system’s application in achieving more precision and control over the temperature of the
water. The valve simply mixes hot and cold water at a certain temperature, seen in Figure 38,
through separate inlets simultaneously within the same system. The final product of the two sets
of water temperatures allows for a single mixture to exit the third outlet of the valve at a new
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Team Aquemini:
Fall
2009
temperature. This eliminates the method of using the motors to control separate valves for each
inlet and rids the cost of adding a third motor to control the water flow.
Figure 38: Example of Mixer Valve [33]
In the alternate design of the system two motors were used to actuate two valves that were set to
control the flow of the hot and cold liquids respectively, seen in Figure 35. Since then the team
has updated the design and as a result of using the mixing valve mentioned earlier, the decision
was made that a better use of the motors, were to attach one motor to the mixing valve and
another motor to the second valve to control the flow of the liquids seen in Figure 38. By
actuating the mixing valve the user and team can have direct control over the temperature of the
water and no longer have a need to implement a third motor to control the flow of the water
through the system, since a second motor can be used for that purpose.
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2009
A motor controlled flow control valve will be placed in line with the exiting flow of the water.
There are currently little to no mechanical setup for the flow control of a shower system. Once
the system is adapted to the current home shower setup, the user can have full control of the
output flow of the shower.
3.9
Discussion
After analyzing and researching the group has concluded that adaptability would be fully
possible with the proposed designs. Based upon the given conditions of water pressure, water
temperature variations, and the capabilities of the preexisting piping system, the prototype had to
be designed in such a manner so as to allow for seamless adaptation and component
configuration compliance. The various components that make up the prototype must be able to
operate in the preexisting conditions of the bathroom piping system. For example, the prototype
utilizes several motor operated valves to control water flow. The typical home plumbing system
has on average 60psi. The design had to be certain that the prototype components were all able to
operate efficiently while experiencing that amount of pressure. Also, the typical home plumbing
system has a cold water temperature that can be as low as 30°F in the winter time and increase
significantly to 140°F as a result of the water heater. The valves that the group utilizes for the
prototype must be able to adapt to these conditions and withstand the temperature variations.
Over all, this project is meant to provide a service that is currently only available at a very high
cost. Using the ideas mentioned it will be an ideal system that is commercially viable. Minimal
piping would have to be removed to install such a system. Keeping labor costs low for the
customer.
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Team Aquemini:
4.0
Project Management
4.1
Overview
[Project Management]
Fall
2009
Each group member will be assigned a task to perform that fits their strengths accordingly. The
conceptual and structural design, programming, testing and writing the report will all be split
amongst team members. The goal of this group is to develop a well implemented work ethic and
well organized development team to produce the project in a timely and efficient manner.
4.2
Breakdown of Work into Specific Tasks
Parts List and Cost Estimate - the group will gather and list the parts needed for construction and
the estimated costs of the project.
Calibration of Testing Apparatus - before fully designing the actual prototype, a testing model
will be constructed beforehand. This apparatus will be designed to calibrate and partly be used to
implement the programming of the user interface and motorized control sequences of the ball
valves.
Program Development - The design of this program will be the control panel that will control all
parts of the prototype from setting a desired temperature to intensifying the water flow.
Circuitry Implementation - Along with programming the user interface, the circuitry will be
designed and implemented into the system that will help control the current and amount of
voltage passing into the system.
Construction of Prototype - the final construction of the prototype will be fully modeled after the
testing apparatus. All of the crucial parts of the system will be fully implemented into a fully
working apparatus.
Error Adjustments - any errors found during the course of the simulation of the prototype will be
addressed and fixed before final presentations.
Senior Design Report - The report would be a report presenting the idea, objectives and give an
updated status on the production of the prototype.
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Team Aquemini:
4.3
Fall
2009
Organization of Work and Timeline
Table 3: Timeline of Project
The completion of the parts list and cost estimate should be done and ready for ordering by the
final week of April. The group is to analyze which parts are needed to complete the project and
gather the necessary funding to purchase the parts.
Calibration of the testing apparatus will begin in May and carried out for 3 weeks. All data are to
be recorded for later use in implementing the program for the user interface. Key parts for this
apparatus must be in place before conducting experiment.
Program development and circuitry implementation- All data previously collected shall be used
to develop a program that would be used to operate the user interface and fully implement all
necessary components together. The circuitry should be completed before program development
takes place.
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Team Aquemini:
4.4
Fall
2009
Breakdown of Responsibilities Among Team Members
Alberto Garcia: Responsible for component selection and purchase of all pneumatic and
hydraulic equipment including: hoses, fittings, pressure regulators, and valves. Generated
engineering drawings pertaining to thermal and fluid systems. Responsible for the design of the
shaft adapter. Used simulation software for stress and force analysis on certain components of
the prototype. Assisted in the assembly circuitry, by soldering and analyzing schematics. Led the
assembly of the hydraulic and pneumatic components of the prototype. Wrote sections of the
report pertaining to relevant project responsibilities. Organized the final report.
Lorenzo Green: Responsible for component selection and purchase of all electric and digital
equipment including: motor controllers, displays, converters and extensions. Generated 3D
engineering drawings of control panel, valves, stepper motors and circuit boards. Design of the
control panel. Led the assembly of circuitry, soldering and analyzing schematics. Wrote the main
portion of the programming code to control the stepper motors. Wrote sections of the report
pertaining to relevant project responsibilities. Organized the final report layout.
Vladimir Louidor: Assisted with writing the sections report including heat transfer, literature
survey and conclusion, helped obtain technical information regarding the stepper motors.
4.5
Commercialization of the Final Product
Simplicity and the ability of an individual to control their temperature preferences on machines
are highly desired applications in the technologically driven market. The design of the product is
meant to be a low cost alternative to the high cost product that has already been made available
on the market today and is marketed towards higher income individuals. The design will be
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2009
marketed toward individuals with modest incomes, who enjoy applications that bring a level of
simplicity into their lives while enjoying the luxury that has only been previously tailored
towards high end individuals.
The digital, touch less, shower assembly will be marketed as an adaptive system. Marketing the
product as an adaptive system as opposed to requiring a complete overhaul of the current home
plumbing setup is a great cost effective alternative. The final product will have the cost saving
ability to be purchased as an aftermarket component to complement the current plumbing system
of the home owner. The digital shower design project only requires minimal modifications to the
current plumbing system to ensure correct functionality. Modifications of the current system
include: additions of control panel, electrical motors, motor controllers and an available power
supply.
4.6
Discussion
It is hoped that the group designs a product that consumers are intrigued by. The design’s simple
to use features and low cost will hopefully prompt median income home owners who want to
experience an upscale shower system to purchase such a cost effective product. The system is
meant to provide consumers with a low cost alternative to the type of luxury shower systems that
are out in the market. By designing this system the group will be improving upon a system that
is currently not cost effective, does not place emphasis on the cost of maintenance over the long
term and in doing so will be adversely affecting the consumer and turning away potential buyers.
The goal is to market this product to a broad user base, currently systems that already exist in
today’s market simply tailor to high end home owners. So obviously the product itself is a high
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2009
end user device. As a would-be company the priority is to tailor the design to middle class
families, who don’t want to pay for an expensive system that does not take into account the
installation fees nor labor fee. These systems also have high maintenance costs, which is a
component that many consumers think about when making an expensive purchase, with Team
Aquemini’s system they would have less to worry about.
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Team Aquemini:
[Engineering Design and Analysis]
5.0
Engineering Design and Analysis
5.1
Shaft Adapter Design Analysis
Fall
2009
Material selection for the shaft adapters was determined through COSMOSWorks. A static
analysis simulation was carried out applying the maximum torque the stepper motor was capable
of. Knowing that the most common materials in a machine shop are either aluminum or carbon
steel, simulations were run using both materials to choose the best alternative. Once knowing
the load, restrictions and yield strength, choosing the material of the shaft adapter was obvious.
Aluminum would comply with the fit form and function, it s a lightweight material and does not
rust. This is advantageous being as this design has contact with water. Figures 39 and 40 show
the data collected after the simulation was carried out. Using the results from the engineering
software COSMOSWorks allowed for an insight of how the shaft adapter would react under the
applied loads.
Figure 39: Stress Analysis for an Aluminum Key
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Team Aquemini:
Fall
2009
Figure 40: Stress Analysis for a Carbon Steel Key
To verify that the software results and calculations were taken correctly, hand calculations were
carried out and an error analysis was taken.
Maximum shear stress
Torque
Outer radius of the shaft
Polar moment of inertia
Knowing the torque the motor would output, the design came down to picking a radius that
would handle the load. With
The value for
with
. This is the shear stress the shaft adapter will
experience under the given torsional loads. Given that the yield strength of aluminum is
, the aluminum key design is well over design failure point.
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Team Aquemini:
Fall
2009
After an engineering drawing was developed, it was given to the manufacturing center for a cost
estimate. After the machinist reviewed the drawing, he calculated that it would take about 2
hours to manufacture the key. Including cost of material and labor, the key was quoted at $40.00.
Since two keys were required, he offered to do the first one at no cost. Because monetary funds
were running low, it was decided that each key would be manufactured at different machine
shops are avoid costs altogether.
5.2
Heat Transfer Analysis
Heat transfer is the flow of thermal energy from a warm object to a cool object or environment.
When a temperature differential exists between separate objects and or their surroundings, the
transfer of thermal energy takes place until thermal equilibrium is reached.
This process
continues until both bodies reach a steady, equal temperature. Thermal energy transfer always
occurs between objects at different temperatures, especially between an object of a higher –hotter
temperature and that of a cooler temperature. There are three basic modes of heat transfer,
conduction, convection, and radiation.
Conduction is the transfer of heat that is in direct contact to other particles of matter. Transfer of
energy could occur by elastic impact such as those that occur in fluids or by free electron
diffusion most commonly found in metals. Fundamentally, heat is transferred by conduction
when adjacent atoms vibrate against one another, or as electrons move from atom to atom.
Conduction is a phenomenon that occurs in solids more easily since the atoms are in constant
contact with one another. On the other hand in liquids (with the exception of liquid metals) and
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Team Aquemini:
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2009
gases, the molecules are usually further apart, which makes it less likely that the molecules
would be colliding and passing on thermal energy [34].
Metals (particularly copper, platinum, gold, iron, etc.) are the most practical conductors of
thermal energy. This is due to the way that metals are chemically bonded: metallic bonds (unlike
covalent or ionic bonds) have free-moving electrons which are able to transfer thermal energy
rapidly through the metal.
Several other physical characteristic of matter that has an effect on heat transfer is the object’s
density and pressure. As the density decreases so does the potential conduction that may occur.
Hence, fluids and gases are less conductive. This is due to the large distance between atoms in a
gas: fewer collisions between the atoms means less conduction. Gases behave much differently
due to its physical properties, conductivity in gases increase under increasing temperature.
Conductivity increases with increasing pressure from vacuum up to a critical point that the
density of the gas is such that molecules of the gas may be expected to collide with each other
before they transfer heat from one surface to another. After this point in density, conductivity
increases only slightly with increasing pressure and density.
To properly calculate the amount of heat transfer or conduction rate, a few principles must be
understood. The temperature difference causes heat transfer qx to travel in the positive x
direction. Qx is a dependent variable, that relies on the known measurement of a particular
object, such as ∆T the temperature difference and ∆x the length of the object, and A the cross
sectional area [34].
There are three possible scenarios to which can be observed about the behavior of qx. Holding
∆T and ∆x constant and changing A, qx will then be directly proportional to A. If ∆T and A are
held constant and ∆x is allowed to change, qx is now inversely proportional to∆ x. Finally, if A
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2009
and ∆x are held constant then qx is now directly proportional to ∆T [34]. The effect of these
varying variables can be summed in one equation:
When the material is changed for example from metal to plastic, the conductive properties of the
materiel have to be taken into consideration. Although the proportionality equation remains the
same, equal values of A, T, and
x, the value of qx would be smaller for the plastic material.
Hence a new variable that takes into account the behavior of any material is:
Where k is the thermal conductivity (W/m · K) of the material. This can then be rearranged and
interpreted as the heat flux:
The minus sign in both equations is to indicate that the heat transfer always occur in the direction
of the decreasing temperature. Fourier’s law equation, states that the heat flux is a directional
quantity, for instance the direction of the heat flux is normal to the cross sectional area A, known
as an isothermal surface [34]. This equation can now be rearranged to represent a more
generalized conduction rate equation in the form of a vector quantity:
is the three dimensional del operator and T(x, y, and z) is the scalar temperature field. It is
implied that the heat flux vector is in a direction perpendicular to the isothermal surfaces [34].
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This can be shown by an alternative version of Fourier’s law that takes into consideration the
direction
of the heat flux denoted by
:
The heat flux vector equation can also be resolved into components in Cartesian components
with several general expressions:
Each expression depicts the relationship of the heat flux across a surface to the temperature
gradient in a direction that is perpendicular to the surface. It can also be observed that the
medium that the conduction occurs in is isotropic (uniform in all directions), meaning that the
value k is independent of the coordinate direction [34].
The second mode of heat transfer is called Convection. Convection heat transfer involves the
transfer of heat between a solid surface and a nearby gas or fluid that is in motion. As the fluid
flows by quickly the transfer process increases. Unlike conduction, there exist two kinds of
convection:
Natural Convection - This method occurs when fluid motion is caused by buoyancy forces that
result from density differences due to temperature discrepancies in the fluid.
Forced Convection - This mode occurs when a fluid is forced to flow over the surface of an
object by an external source such as fans and pumps. Creating an artificial forced convection of
heat transfer.
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The formula for Rate of Convective Heat Transfer:
Where A is the surface area of heat transfer, Ts is the surface temperature and Tb is the
temperature of the fluid at bulk temperature. However Tb although with each situation and is the
temperature of the fluid “far” away from the surface. The h is the constant heat transfer
coefficient which depends upon physical properties of the fluid such as temperature and the
physical situation in which convection occurs. Therefore, the heat transfer coefficient must be
derived or found experimentally for every system analyzed.
Earlier in this section, the principle of thermal conductivity was briefly discussed along with the
importance of the behavior of different material in relation to amount of heat transfer that can
flow from one matter to another. The thermal conductivity is one of the most important thermal
properties of matter that determines the amount of heat transfer that is being released from a
particular matter. Thermal conductivity related to conduction in the x direction can be defined as:
One can also conclude that as the heat flux increases so does the thermal conductivity. In general
the thermal conductivity of a solid is larger than of a liquid or gas [34]. Figure 41 describes the
thermal conductivity for various materials.
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Figure 41: Thermal Conductivity of Common Materials
In the solid state, the transfer of thermal energy is due to two effects; the movement of free
electrons and lattice vibration waves. These effects can be added so that k is the sum of the
electronic component ke and the lattice components kl [34].
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ke is inversely proportional to the electric resistivity ρe. Pure metals (e.g. zinc and silver) have
low ρe, but their ke is much larger than kl. On the other hand, alloys are rich in ρe; therefore, the
relationship between kl and k is no longer negligible. For nonmetallic solids k is determined
mainly by kl, a characteristic that depends on the frequency of interaction between the atoms of
the lattice [34].
For insulation systems, thermal insulations are made of low thermal conductivity materials that
are combined to achieve a low end thermal conductivity system. Materials such as fiber, power,
and flake type insulators the solid material is delicately dispersed into an air space. Systems like
these effective thermal conductivity, which is dependent upon the value of k and the radiative
properties of the material’s surface as well f the gas and volumetric fraction of the air space that
it will occupy. This type of system also involves the dependency of the bulk density (solid
mass/total volume) a property that depends heavily on the way the solid material is formed [34].
Foamed systems have small and hallow spaces created from the bonding or fusion of the thinly
solid material previously mentioned, that creates a rigid matrix, called cellular insulation.
Reflective insulation is comprised of multilayered, parallel, thin sheets or foils of high
reflectivity, reflecting back radiant energy back to its source [34].
Finally it is important to recognize that heat transfer through these insulted systems can take on
several modes that may include:
o Conduction through the solid materials.
o Conduction or convection through the air in the void spaces.
o Radiation exchange between the surfaces of the solid matrix especially if the temperature is
very high.
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In the fluid state the space between molecules is larger. Due to the larger amount of space
between the molecules, the motion of the molecules is more random in fluids then in solids,
therefore thermal energy transport is less effective. The thermal conductivity of gases and liquids
is now smaller then in solids.
Figure 42: Three Heat Transfer Modes
The materials involved in the shower system utilize several different metals including copper,
brass, polyvinyl chloride (PVC) plastic, and aluminum. Copper is the material of the mixing
valve and the water flow valve is composed of brass. The plastic tubing that is being used for the
fluid delivery is made out of polyvinyl chloride. While the two tanks are produced by a
manufactured brand , Igloo, that uses its own insulation material called Ultratherm insulation.
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The thermal conductivity of the polyvinyl chloride plastic tubing is approximately 0.19 (W/mK)
at 25°C. Given the fact that the tubing is clear plastic, there will be a heat loss through the
system. The type of heat transfer that is accumulating in the tubing is forced internal convective
heat transfer. Two convective heat transfer phenomenon are occurring in the fluid delivery
system; 1) from the fluid to the surface of the tubing and 2) from the surface of the tubing to the
environment. The rate of convective heat transfer can be found through the formula;
Since heat gained or absorbed is positive while heat lost is negative, a negative sign must be
positioned on the heat lost for the equation to hold.
- Heat Loss
– Mass
- Specific Heat
- Temperature Change
For example, if it is desired to mix 50 g of water at 30 °C with 50 g of water at 10 °C
To find the final mixed temperature it is necessary to apply the given formula.
Figure 43: Example Mixing Chamber
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(30g)(4186 J/kg)(
(
- 10 °C) = - (
- 10 °C) = - (30g) (4186 J/kg) (
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- 30 °C)
- 30 °C)
= (30 + 10) °C
= 40 °C
= 20 °C
It can be seen here that as long as the mixture of water is kept equal and neglect the differences
of density, the final mixed temperature is an average between the hot and cold water. The actual
will differ from this value because of some heat loss to the container.
5.3
Component Design Analysis
A major factor in the design of the prototype is the tank storage system. Simulating the pressure
in the water tanks was necessary in order to establish a value of the pressure applied into the
tanks. After the water tanks were drawn to scale using Solidworks, a COSMOSWorks pressure
analysis was carried out. Simulating the pressure, the first component that would fail would be
the lid as can be seen in Figure 44 that the lid has the largest displacement. Once these values
were obtained it was established that the pressure would not be regulated larger than 5 psi to
avoid possible rupture of the tank lid and injury to the team members.
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Table 4: Data and Results of Pressure Analysis on Water Tanks
Name
Type
Min
Location
Max
Location
Displacement1
URES: Resultant
Displacement
0m
(2.59042 in,
6.37894e-008 m
(-0.507391 in,
Node: 3687
-5.41024 in,
Node: 480
7.4175 in,
-1.88396 in)
Stress1
VON: von Mises
Stress
0.279034 in)
7.23128 N/m^2
(-0.623982 in,
1854.16 N/m^2
(-2.1571 in,
Node: 4393
-3.3769 in,
Node: 13996
-3.00524 in,
2.69068 in)
Strain1
ESTRN:
Equivalent
Strain
3.83126 in)
2.76549e-009
(-0.623982 in,
7.09094e-007
(-2.1571 in,
Node: 4393
-3.3769 in,
Node: 13996
-3.00524 in,
2.69068 in)
Figure 44: Displacement Analysis Results
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Figure 45: Stress Analysis
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[Prototype Construction]
6.0
Prototype Construction
6.1
Description of Prototype
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Incorporation of the knowledge obtained from courses such as transport phenomena and design
of thermal fluid systems has allowed for such systems to be used in this design project. Selection
of the containers that held that water required calculations pertaining to how much pressure they
would be able to handle. After researching various water containers, taking into account size and
cost, it was decided that a commercially available water thermos would be one of the best
options. The thermos reviewed could contain 2 gallons of water and provided insulation warm
water reservoir. Knowing that these thermoses’ need be pressurized in order to transport the
water from the tanks to the shower head, formulation was carried out by means of the equation
,
being pressure,
as force and
as area. Measuring the radius of the thermos’ lid,
the effective area was found to be
. Having a constant
source of pressure, calculating the force the lid would experience was now possible. Estimating
that the lid would be able to withstand about 70 lbs of force, it was only a turn of the knob on the
pressure regulator to maintain the force under this threshold. Using
and
the pressure regulator was set to maintain a value of
with
.
Allowing the pressure to be any higher than this would most likely cause the lid to burst off of
the thermos, therefore, prior engineering design calculations, as seen in the previous section,
were necessary to prevent such accidents.
Not only did the thermos need to be able to withstand the accumulated pressure, but also the
other components that supplied, regulated and transported the operating pressure. Fittings, hoses
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and regulators all need to be rated to be able to perform under the given pressure. Knowing that
the thermos’ lids would only be able to hold a pressure of 2 psi research for the remaining
components began. It was found that due to the low pressure of the system an extremely wide
variety of the components could be selected. Further research led to the conclusion that
components that could operate at high pressures (1000 - 3000 psi) where significantly more
costly than low pressure components (100 -500 psi). After analyzing the cost, the selection
process was finalized. All pneumatic components were selected and purchased from the Grainger
Industrial Supply catalogue. Knowing that extensive testing and calibration would require a large
amount of time for this project, a constant supply of compressed air would be needed to
pressurize the thermos and transport the water from the tanks to the shower head. The most
accessible compressed air line was found to be in the student machine shop. The fittings that had
to be purchased were selected by first knowing why type of connections the air line had.
Figure 46: Pressure Regulator with Mounted Fittings
Assessment of this connection was taken and a quick disconnect fitting was selected.
In order to assure a low number of components to keep cost low, connection compatibility
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between system components was necessary research. Grainger provided a great stop for most of
the supplies utilized, they had a wide selection of size and type of connections. Figure 47 shows
the section of the Grainger catalogue used to select the industrial plug used to connect the
compressed air line to the air pressure regulator. For the two components to connect seamlessly,
one of the coupler ends had to be a 1/8 Male NPT thread. This ensured an easy connection to
supply air to the rest of the system.
Figure 47: Grainger Industrial Supply Catalogue Pg.3308 [35]
The use of Teflon tape in this design project was crucial. Air loss as a result of not using the tape
was significant and after this was found, action was taken immediately. Teflon was used on all
tapered threaded (NPT) connections, the teflon served to fill the spaces between each individual
thread where air was initially escaping. All connections into the pressure regulator required
teflon, as all the inlets were 1/8 female NPT. Plumbing sealant was also used along with using
teflon tape to minimize air leaks. The sealant was used in the areas where holes were drilled and
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bulkhead fittings were used, along with o-rings as seen in Figure 48, the sealant provided a leak
free area.
Figure 48: Preventing Leaks Using Sealants
Once all the fittings had been installed, the air hose assemblies were ready to begin. Rubber hose
was chosen for its low cost and it flexibility, after an ideal hose length had been determined a
razorblade was used to shear the hose into the number of pieces required. To complete the hose
assemblies barbed swivel fittings were fixed into a vise, lubrication (DW-40) was sprayed onto
the barb and the hose was forced to slide over the barbed fitting. This process can be seen in the
hose assembly in Figure 58. Now that hose assemblies were complete, all pneumatic system
components were able to be interconnected. The 37 seat angle provides a seal without the need
of teflon tape, slightly tightening these flared fittings provides an efficient and simple method of
assembly and disassembly for the system components.
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Figure 49: Hose Assembly
6.2
Prototype Design
At the 75 percent milestone of the design process, all of the components pieced together will
appear as illustrated in Figure 50.
Figure 50: Constructed Prototype Design
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Figure 50 illustrates the setup of the stepper motor with the modified mixing valve faucet. A
control box has been fabricated to house the Bistep2A controller and the Board of Education. A
feature of the control box is that it protects the sensitive electrical controllers from being
damaged from water. The control panel is connected by wire to the Board of Education, stepper
motor, and the BiStep2A motor controller.
6.3
Prototype Components
Several electrical components were required for the correct operation of this design project;
infrared sensors, stepper motors, motor control board, A/D converters, BASIC stamp circuit,
temperature sensors and LCD displays. All of these components were pivotal in the construction
of the digital shower.
A 3290 pin solderless breadboard served as the foundation of the electrical circuits for the
project. Attached to the breadboard were the four QTI sensors, various resistors, A/D converter,
temperature sensor and I/O switch.
The staple feature for the design project was to create mechanical movement from digital inputs.
For example, the digital input signal generated from the user triggering the infrared sensors
would function as the electronic switch that would enable the movement of the respective stepper
motors. A triggering of one of the four infrared sensors would result in the water flow either
increasing or decreasing, or the water temperature to either cool down or warm up. Four Parallax
QTI infrared sensors were utilized to serve as electrical input signals. Figures 8 and 9 gives an
illustration of the actual QTI sensors as well as the circuitry of the sensors, respectively.
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In addition, analog data input would have to be converted to digital data. This digital data would
then be output as relevant numerical values that would be readable to the user via an LCD
display screen. The retrieval of data in the analog state and the conversion of this data into a
digital state is performed via an analog to digital (A/D) data converter. The 8-Bit serial I/O A/D
converter.
The date to be converted within the A/D converter originates from an LM34 Temperature
Sensor. See Figure 14. This temperature sensor is responsible for measuring the temperature
within the outlet pipe of the shower system. The temperature sensor will be covered in heat
shrink material and then heated to reduce the heat transfer from convection, namely, inside
surface of heat wrap material to surface of temperature sensor. The LM34 is a precision
monolithic temperature sensor. It has an output of 10mV/°F with a typical precision of ±.35°F
over a -50 to +300°F temperature range. The sensor is accurate to within ±0.4°F at 77°F.
To display the temperature readings taken from the LM34 sensor, an LCD (shown in Figure 16)
was connected to the system. Testing the operation of the LCD was fairly straightforward. Figure
51 shows the early stages of programming for the display, in this sample QTI sensors were used
to test whether or not the sensor was operational and see if it was feasible to use it as a user
interface to control the flow and temperature of the water throughout the system as mentioned
earlier in this section. In Figure 52 the board of education circuit set up and wiring has been
implemented to conduct experimentation of the temperature sensor utilizing a fully developed
testing program seen in Figure 51. The LCD displays the temperature reading with help from the
A/D converter that reads the temperature from the sensor in volts. Each 10mV equals to 1
degree, once the converter reads it, the output temperature on the display is converted to digital.
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Figure 51: Sample LCD Testing Program
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It is important to note that the programming code only represents a portion of what is intend for
the application to do. The code in Figure 51 will have to be incorporated into one program so
that the system is entirely functional. Experimentation of all codes and actual operation will still
have to be conducted before simulation.
Figure 52: Temp Readout on LCD w/Temp Sensor
The Board of Education is the control board used for operation of the entire system. The BOE
connects directly to the user input, infrared sensors. It is the primary control board for this
project. It has a 2.1mm center positive plug and a 9-volt battery power supply connection. Three
connections are mechanically linked to prevent dual connections. An on board regulator for the
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BOE delivers up to 1 amp of power for the project. This amperage usage is critical for
determining the total amount of supply amperage needed for the system.
Figure 53: Board of Education [19]
The BOE has 16 I/O pins that are used for the programming of the board, and for the connection
of the electrical components to the mechanical ones. These 16 I/O pins are labeled P0-15. In
addition to these pins, several connections are available for Vdd, Vin, and Vss controls. The
BOE operates by means of BASIC Stamp IC programming.
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The secondary control board is the BiStep2A Motor Controller. This motor controller is a
proprietary controller from Peter Norberg Consulting, Inc. It has the capability to control one or
two motors, either unipolar or bipolar, simultaneously. It has a maximum motor supply voltage
of 45V and a maximum logic supply voltage of 15V. For the design project, a maximum
combined supply voltage for both the motors and the logic is 12V. To calculate for the current
needed to supply to each motor, several steps would need to be followed. The first step would be
to determine the individual motor winding current and voltage requirements. The desired
winding current for each motor is specified by the motor manufacturer. The two bipolar motors
used for the design project were manufactured by JameCo Electronics. There is a rating of 0.16A
for each motor. Since the project is using a non-current regulating microcontroller, the current
that actually flows through the windings of the motor will be based on the voltage of the power
supply chosen and the resistance in the windings. Using the resistor-only based formula V=IR
and rearranging it to find I, I=V/R. V is the voltage of the selected power supply, in this case 12
volts, and dividing that by the resistance in the windings of the motor, 17 ohms. The calculations
gives a value of 0.16 A, exactly what the manufacturer suggest, sometimes the acquired value
maybe higher then what the manufacturer recommends, fortunately in this particular situation it
is not. For the type of motor being utilized by the design project, a 6-wire unipolar motor, it was
necessary to measure the resistances of each winding relative to each other. A diagram was then
constructed to aid in the calculations of the current.
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Figure 54: Motor Winding Resistance
From the measured resistance one can tell which leads are the common leads (wires that would
be grounded), if the measured resistance of those wires; yellow and orange read close to zero
then those wires would be the common leads. The group reaffirmed its findings by further
experimenting with the common lead wires. By measuring the resistance between the common
wires and the four remaining wires, the group was able to read the values shown in the table
below. Measurement of the resistance values across the green wire and the orange and brown
wires, yielded values of 75 and 150 ohms respectively. The wires with double the value belong
to the opposite ends of a given winding. If infinite or large values were given then the wiring
pairs would have belonged to different windings. For example if the resistances between the
orange and red wires were measured, high resistance readings would’ve been obtained which
meant that the red wire would’ve belonged to a completely different winding. In Figure 52, the
wires were paired that belonged to each winding and proceeded to connect them to the Bistep2A
motor controller.
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Once the resistances for the motor windings were found, Ohm’s law was then used to calculate
the voltage and current requirements for the system. Because of the complicity of the BiStep
Motor Controller board, there are four methods in which the motor can be controlled. Control
can be performed using a single winding full step method, a half step alternate winding method,
full step, and a microstep winding method. The method decided upon for the design project is
single winding full step. This is more advantageous due to the low current usage requirement.
Table 5: Current Multipliers
Once the winding setup was determined, the next step would be to determine the voltage for the
motor power supply. It was suggested by Peter Norberg Consulting to use a power supply with a
voltage greater than or equal to the nominal for the JameCo motor. However, this power supply
would have to be less than or equal to the maximum voltage supported by the controller. Higher
voltages increases the top speed of the motor, but also requires a more extensive power supply,
which in turn would make the BiStep2A Motor Controller run hotter. Also, as a general rule of
thumb, the voltage for the power supply should be between 1.15 and 10 times that which would
be required to run the motor with a non-current regulating power supply. The suggestions made
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by the manufacturer left quite a large selection range for power supplies. Another requirement
that must be accounted for is the logic supply current.
Table 6: Controller Boards
The BiStep2A board required the greatest amount of current, when compared to all of the other
motor controllers. When all of the voltage and current requirements were taken into account, a
final decision was made as to the power supply.
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Figure 55: Project Power Supply [36]
An Enercell 6-12VDC was selected to provide regulated, filtered power to the entire system. The
power adapter delivers up to 2.5A. For experimentation purposes the prototype will be
implementing two power supplies. The voltage supply will simply consist of a wall mounted 12
volt plug that will be configured into the wiring diagram to power the microcontroller, while the
board of education will be powered by a 9 volt battery. To prevent any wiring and ground issues,
a single power supply will be used to power both microcontrollers.
Since the prototype will be using one power supply to operate the entire arrangement of
components, the logic requirements of each microcontroller will have to be accounted for. The
Bistep2A and the Board of Education have logic requirements of 1A and 0.003A [20],
respectively. Configuring the wiring of the motor microcontroller was at first confusing given
there were only two wires present, while the controller had 6 inputs. Connecting the wires any
other way would have severely damaged the controller. By contacting the vendor for more
guidance on the wiring of the adapter, the following diagram was produced.
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Figure 56: Wiring Diagram
Since the power adapter only had two wires; a positive and a negative, the idea was to connect
three positive wires and three negative wires to the indicated connectors. To implement this
configuration , two wires were soldered, the positive wire of the adapter and another two to the
negative wires, for a total of six wires.
Component selection for water flow was carried out and assembly of the hydraulic assembly
began. Figure 56 shows the assembly process step by step. Since the two ends of the hose
needed different fittings, this assembly required two different processes to assemble, unlike the
air hoses which were the same at both ends. Figures 56 and 57 show both processes.
Figure 57: Clamped Hose Assembly
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Cutting the hose to a
certain length.
Lubricating the barb
to ease the insertion
process.
Uniting the hose and
the barb by force.
Figure 58: Water Hose Assembly Process with Swivel Fitting
Slide hose onto
fitting
Apply clamp and
tighten with a
screw driver.
Completed
assembly.
Figure 59: Water Hose Assembly Process with Clamped Fitting
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Figure 60: Final Water Hose Assembly
Recreating realistic effects of a shower required supplies of water with a significant temperature
difference. In order to achieve this difference in temperatures, ice was added to the cold water
thermos and a water heater was inserted into the other tank to raise the temperature and increase
the difference. Figure 61 shows the heating element that will be used to increase the water
temperature, it will be placed at the lowest position possible in order to maintain itself
submerged until the water tank is completely emptied. Having to connect the heater to an
electrical source posed a problem, to which Team Aquemini sought a solution. Since the water
tanks hand to be completely sealed to maintain pressure, drilling a hole for the heater’s power
cord was carefully thought out. First, the power cord was cut in two pieces and the thinnest was
measured. A hole that would accommodate the thin section of the cord was drilled and the cord
was passed through. Once through, the positive and negative terminals were soldered back
together and protective heat shrinks were used to wrap the initial cuts.
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Figure 61: Heating Element
Incorporation of a digitally controlled shower system required a system of motorized valves
being controlled by the user in the shower. The approach taken to achieve these actions was to
program a low torque, inexpensive stepper motor and somehow attach it to the knob of a mixing
valve and the flow control valve. A shaft adapter was reverse engineered to meet the fit, form
and function of the motor and 2 valves. For simplicity, valves that were easiest to open and close
were chosen, as these valves required less torque. Since the low torque requirements equaled to a
smaller power supply the cost of the overall design was able to be kept low.
Temperature adjustments were controlled by the stepper motor attached to the mixing valve. The
initial shaft adapter design was meant to use only two set screws on the shaft of the motor the
other end would be machined to fit the end of the valve. From a machinist view, this design may
have been over engineered and a faster, simpler alternative was taken. Applying two set screws
to the valve end, this eliminated the need to machine an end to fit the knob, which was a task far
more difficult to perform. Figure 62 illustrates how the motor is connected to the shaft adapter
and how it can transfer the rotation from the motor shaft to the valve knob. The same idea was
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applied to the flow control valve and since the same model motor was used to control flow, the
only difference in design for the used to control the flow was the diameter of the orifice that fit
over the knob of its respective valve.
Figure 62: Motor with Shaft Adapter
Via the user inputs, the motors will respond and turn a certain direction. While one motor is
turning the mixing valve knob the other is in control of the flow control knob. These inputs
ultimately determine the flow intensity and temperature of the water desired by the user.
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Figure 63: Temperature Control Valve
Figure 64: Flow Control Valve
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Figure 65: Thermal/ Fluid System Diagram
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6.4
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Programming of Prototype
To make all of the mechanical components, input sensors, signal converters, and infrared devices
work cooperatively, all of the devices would need to be controlled by a computer program. This
program would be required to effectively synchronize all of the inputs to the output motors. The
program would be required to allow for various output motion of the motor based upon the user’s
live interaction input. Two devices must be programmed to allow for user input, and to
communicate between each other; the Board of Education and the BiStep2A Motor Controller.
The BiStep2A motor controller board system can be operated using the firmware known as
GenStepper provided by the manufacturer. The programming for the motor controller can be as
simple as a command to slew the motor left or right, or to stop instantaneously. Conversely, a
more complex programming string can be developed to deliver sequential control over several
steps. The BiStep2A motor can be operated in serial command, direct control of the motor
controller via a serial link to a PC. The BiStep2A can also operate in TTL mode, which is in
tandem with another BASIC Stamp microcontroller in which input and output signals are sent to
the BiStep2A via two I/O pins. For serial control of the motor controller, the following are a
quick summary of commands
0-9, +, - – Generate a new VALUE as the parameter for all FOLLOWING commands
A – Select the Auto-Full Power Step Rate
B – Select both motors
E – Enable or Disable Remote Direct Pulse Control
G – Go to position x on the current motor(s)
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H – Operate motors at ½ power
I – Wait for motor „Idle‟
K –Set the "Stop oK" rate
L – Latch Report: Report current latches, reset latches to 0
M – Mark location, or go to marked location
O – step mOde – How to update the motor windings
P – sloPe (number of steps/second that rate may change)
R – Set run Rate target speed for selected motor(s)
S – start Slew
T – limiT switch control (firmware versions 1.65 and above)
V – Verbose mode command synchronization
W – Set windings power levels on/off mode for selected motor
X – Select motor X
Y – Select motor Y
Z – Stop current motor
! – RESET – all values cleared, all motors set to "free", redefine microstep. Duplicates
Power-On Conditions!
= – Define current position for the current motor to be 'x', stop the motor
? – Report status
other – Ignore, except as "complete value here"
The slew (S) command is one of the more important commands for the project. This command
tells the motor to rotate indefinitely in the indicated direction. For example, +s will cause the
motor to move forward or in a counterclockwise direction and a negative sign will have the
opposite effect. A numerical value in front of the “s” executes a “relative seek” command, it
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largely depends on the current location of the motor and the target location. For example if the
current location is 1000 and a slew command such as -500s is implemented, the motor shaft will
move to position 1000-500=500.
The program presented in Figures 65 and 66, will be implemented differently so that the correct
direction and location is represented.
X: The “x” command lets the microcontroller board know which motor to control. In this case
this command is to control the motor attached to the X inputs of the microcontroller board.
Z: This Command tells the motor to stop. The configuration in the program “xz” tells the X
motor to stop moving if the “ELSE” condition(s) is true.
By using a connection to a BASIC Stamp series board provided by Parallax, Inc, the BiStep2A
stepper board can bypass this serial setup configuration and expand the capabilities of the board.
Connection to a BASIC Stamp microcontroller board is via three pins; READY, SERIN, and
SEROUT. Communicatins can be performed via the motor controller and the microcontroller can
be performed at either 9600 baud or 2400 baud rate. The following is a sample code to be used
on the motor controller. This code cycles one motor on a microstep size of 1/64 of full step. The
motor is spin cycled between local positions 2000 and 0. A 1/5 second pause in programmed
between each cycle for visualization puposes.
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Figure 65: Sample BS2 Script
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Figure 66: Sample BS2 Script cont
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Team Aquemini:
Fall
2009
The Board of Education is a complete, low cost development platform designed for aiding in
construction of student learning projects. The Board of Education is developed by Parallax
Incorporated. The BOE is a tool to help get started with Parallax BASIC Stamp ICs. BASIC
Stamp is a family of microcontrollers. The BASIC Stamp has very beneficial control properties.
The small size of the PIC controller and the power and versatility of the controller, along with
extended flash memory, allows for a user friendly programming environment.
The programming language used by the BOE is PBASIC. PBASIC is a microcontroller based
version of the BASIC programming language. This new programming language, created by
Parallax, Inc. was created to bring ease of use to the microcontroller and embedded processor
world. Codes are written to the BASIC Stamp microcontrollers using PBASIC. The PBASIC
programming language has familiar BASIC instructions such as FOR, NEXT, IF, THEN and
GOTO. However, PBASIC has some new commends that are especially useful when using
various inputs and outputs to several different devices.
Several strategies were considered for use to approach the correct programming methodology of
the components to allow for direct, live control of the motors via the motor controller. After
many brainstorming sessions, it was decided upon the use of a simple yet efficient method of
successive IF…THEN…ELSE statements. The following shows a partial script of the entire
motor controller program.
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Figure 67: Motor Control Using QTI Sensor
Thus far, programming the motor to be controlled by the QTI sensors has proven to be a
challenge. The format of the program is to cycle one of the stepper motors in either direction
based upon the QTI sensor that is activated. The program is designed in such a way that the
motor will move continuously until the QTI sensor is no longer activated. This allows for the
user to be able to adjust the position of the mixing valve and the flow regulator valve. Due to the
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fact that the program provides instantaneous response, the temperature and flow of the water will
also respond instantaneously to the user’s input.
6.5
Prototype Cost Analysis
As per the commercialization and objective of the project, the total cost of the prototype must be
kept to a minimum. Much comparative analyzing was performed to select the correct prototype
components that were of at least minimum required quality, performed the correct functions, and
worked cohesively with the other components. Table 6 shows the cost of each component used
with the prototype thus far, as well as the vendor of the component. Total parts purchases come
to a total of $428.85. The majority of the expenses incurred thus far can be attributed to the
BiStep2A motor controller board and the Moen Bath Faucet. The bath faucet will be used as the
primary foundation of this project. All mixing of the hot and cold water will be used via this
faucet, therefore the faucet is a justified purchase.
Given that this is the cost of making a single prototype, a manufactures suggested retail price can
be brought to a significantly lower cost. After researching mass production cost, in general, the
cost that is spent to make a large amount of most products drops about 30 to 40%. Knowing that
the cost of materials for this project can be in the range of $300.00, considering mass production,
the main objective of the team can be met. After visiting various local vendors of similar
products, it was found that the control panel of a simple digital shower control similar to the
group’s prototype cost $1500.00.
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Table 7: Component List
Date
Vendor
8/25/2009 The Home Depot
8/27/2009 Rage Paintball
8/27/2009 Jameco Electronics
8/27/2009 Peter Norberg Consulting
8/28/2009 Grainger
8/28/2009 Grainger
8/28/2009 Grainger
8/28/2009 Grainger
8/28/2009 Grainger
8/28/2009 Walmart
8/28/2009 Walmart
Parallax
Parallax
Parallax
9/23/2009 Radio Shack
9/29/2009 -Parallax
11/1/2009 Jairo Villa
Total
Item
Moen Bath Faucet
Clear 1/2" Hose
Hose Clamps
Barbed Hose Fittings
Adapter
Fitting
Tax
Tank Adapter
Stepper Motor
BiStep2A Board
Air Regulator
Pressure Gauge
1/8" Fitting
Teflon Tape
Tax
2 Gallon Jug
Tax
8-bit A/D converter
Temp Sensor
LCD Display
12Volt 2amp Power
1064 pin Breadboard
Shipping
Control Panel
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Purchased By
Alberto
Alberto
Alberto
Alberto
Alberto
Alberto
Alberto
Alberto
Alberto
Alberto
Alberto
Alberto
Alberto
Alberto
Alberto
Lorenzo
Lorenzo
Lorenzo
Lorenzo
Lorenzo
Alberto
Lorenzo
Lorenzo
Alberto
Cost
Qty Extended Cost
$ 58.00
1 $
58.00
$ 6.67
1 $
6.67
$ 0.95
3 $
2.85
$ 2.75
3 $
8.25
$ 3.26
1 $
3.26
$ 4.47
1 $
4.47
$ 5.85
1 $
5.85
Donated
1
Donated
$ 19.95
1 $
19.95
$ 139.79
1 $
139.79
$ 16.48
1 $
16.48
$ 5.99
1 $
5.99
$ 0.87
1 $
0.87
$ 0.64
1 $
0.64
$ 1.68
1 $
1.68
$ 8.88
2 $
17.76
$ 1.25
1 $
1.25
$ 5.99
1 $
5.99
$ 3.99
1 $
3.99
$ 29.99
1 $
29.99
$ 39.99
1 $
39.99
Donated
1
Donated
$ 10.13
1 $
10.13
$ 45.00
1 $
45.00
$
428.85
Team Aquemini:
7.0
Testing and Evaluation
7.1
Overview
[Testing and Evaluations]
Fall
2009
Testing of the digital shower system was predominantly centered on the digital features of the
shower. The features that allow the user to digitally control the mixing of the hot and cold water
and to control the flow intensity of the outlet pressure was tested for their performance. Recall
that QTI infrared sensors are used to activate the motors which control the temperature mixing
valves as well as the outlet water pressure flow intensity. To activate the motors, the user will
place a finger in the path of the infrared sensor. During the entire length of time that the finger is
placed in the path of the sensor, the motor will continue to cycle. The pressure control motor,
however, will stop cycling once the flow valve reaches either the completely open or completely
closed position.
Testing is also required for the safety system of the prototype. If the product is to be
commercialized with the advertising feature of being safety cautious, it is imperative that the
safety feature is tested. The safety feature implemented within the prototype is a buzzer that will
sound at 89db when a predetermined high temperature set point is reached. The suggested
normal operating temperature of a shower for an adult is 104°F. For an infant child, this
extremely hot water temperature will scorch their skin. A child can be severely scalded in under
a second with a water temperature of around 140°F, which is common in many American homes.
Setting a maximum temperature of 120°F is much safer, as at this temperature it takes five
minutes to severely scald a child [28]. However, for a safe bath, an infant child should be given a
bath in water temperature around 99°F. It is also important to note that not only will high
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temperature water scald the child’s skin, but low temperature water will drop the child’s body
temperature dangerously low. For this purpose, a low level water temperature setting has been
set to 95°F.
In addition to the control of the valve motors and testing of safety systems, the structural
integrity of the system would have to be evaluated prior to commercialization of the prototype.
The prototype is built to operate with 2 gallon Igloo plastic water containers. The containers are
used to replicate the hot and cold water normally supplied by existing shower and tub plumbing.
It has been discussed that as a design alternative, the system can be fabricated to accommodate
the needs of a camping trip, or be used in a remote location where readily available access to a
plumbing supply is nonexistent. In the event that the system could possibly be used for these
purposes, testing of the water tanks must be performed.
7.2
Design of Experiments - Description of Experiments
Testing of the QTI infrared inputs will return data that allows the developer to determine the
angle of the mixing valve based upon the length of time that the QTI sensors are activated. Since
the motor will adjust the maxing valve to control hot and cold water distribution, it is required to
know exactly how many degrees the mixing valve is turned over a given amount of time. For
example, if the user wishes to increase the temperature of the outlet water, the rate at which the
temperature increases is desired to be known. To test this, the prototype was setup to its fully
operational stage. The hot water was heated to its maximum temperature of 86°F. To simulate a
much broader range of temperature variation, the cold water tank as filled with cold water, and
additionally ice was poured within the tank to make it colder. Also, to aid in visually observing
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the water change temperatures from cold to hot, blue food coloring was added to the cold water
and red food coloring was added to the hot water tanks. The tanks were then pressurized to the
normal pressuring amount of ~2psi. The control system was turned on and power was given to
the controls. To determine the elapsed time needed to change the temperature from completely
and full blue water to completely hot and full red water, a testing trial run was setup. The mixing
valve was positioned as to allow only fully cold water to flow. The system was turned on, the
intensity flow valve was set to 75% open, and the water began to flow. One group member was
positioned in front of the control panel to activate the temperature increase sensors. Another
group member was alongside the first group member and has a stopwatch ready to measure the
elapsed time necessary for the water to turn from completely cold to completely hot. The time
required for this change was determined and its results recorded. The findings of these results
are detailed in Test Results and Data section 7.3
For the testing of the safety system high temperature and low temperature buzzer, a more straight
forward approach was taken. The buzzer was programmed within the logic of the system to
alarm at a high temperature of 86°F and a low temperature of 45°F. Based upon the guidelines
outlined in the previous section, high and low temperature setpoints of 120°F and 95°F
respectively would be expected. However, due to the inability of the prototype to reach a high
temperature of 120°F, or even 95°F, the accepted values were decreased to a more workable
temperature range. If this prototype was commercialized to operate within a home setting, it
would be simple to change the high and low temperature alarm points to reflect a more practical
and safe temperature. Prior to production, the logic of the system would reflect the correct 120°F
and 95°F alarm setpoints. For the purposes of the prototype, the modified temperature setpoints
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are sufficient. The safety alarm buzzer works directly with the temperature reading sensor. Once
the sensor detects the temperature of the water to rise above the high alarm setpoint or below the
low alarm setpoint, the buzzer is programmed to alert the user by buzzing at a frequency of
6400Hz and 89db. The findings of these results are detailed in Test Results and Data section 7.3
To determine the safest water pressure that the Igloo brand water coolers can withstand, the
group decided to pressurize the prototype to a conservative level. When given a pressure of
10psi, the lid of the water cooler deformed by approximately a half inch. Unknowing of the total
amount of pressure that the tanks was capable of withstanding, it was decided to keep the
pressure around a safe range of 2 psi.
7.3
Test Results and Data
The initial testing of the changing of the water temperature from cold to hot returned values that
were close to the unacceptable range. The determining basis of acceptability for the mixing valve
control was based on the time it takes to make a full cycle from cold to hot water. If the cycle
time was too quick, it would mean that the system was too sensitive, and an accurate and reliable
control of the temperature settings is not achievable.
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Table 8: Temperature Trial Analysis
Position In Degrees
0
20
40
60
80
100
120
140
160
180
200
220
240
260
280
300
320
340
350
Experimental Data
Temperature ( ̊F)
Trial 1
Trial 2
46
44
47
48
50
51
52
52
55
56
57
59
60
62
62
65
64
66
65
67
69
71
71
72
74
75
76
76
78
79
81
81
82
84
84
85
85
86
103
Average
45
47.5
50.5
52
55.5
58
61
63.5
65
66
70
71.5
74.5
76
78.5
81
83
84.5
85.5
Fall
2009
Team Aquemini:
Fall
2009
Temperature Vs. Angular Position
90
85
Temperature ( ̊F)
80
75
y = 0.1159x + 45.959
70
Trial 1
65
Trial 2
60
Average
55
Linear (Average)
50
45
40
0
50
100
150
200
250
300
350
400
Position in Degrees
Figure 68: Temperature vs. Position Analysis
The results of the first test showed that once the user activated the QTI sensor to control the
motor to change the water temp from cold to hot, the time it took for the water change cycle was
approximately three seconds. A total water temperature change of 39°F was experienced. This
means a typical temperature increase of approximately 13°F per second that the QTI sensor is
pressed. This is too quick of a temperature change to be able to select a desired temperature with
ease. As a result, modifications were made to the stepping motor stepping time. The previous
stepping time of the motor was 1/16th of a step. In order to lengthen the time required to make a
complete cycle of cold to hot water, the stepping rate of the motor would have to be decreased.
Within the logic of the stepping program, the rate was changed from 1/16th of a step to 1/64th of
a step. The step change resulted in an elapsed time increase of 17°F. This new cycle time is more
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acceptable and will be the final design of the prototype. Figure 68 shows a graph of the
temperature increase of the outlet water as a function angle that the mixing valve is positioned.
To test the temperature safety system, a high alarming setpoint and low alarming setpoint was set
to 86°F and 45°F. The user of the system then systematically increased and decreased the
temperature of the outlet water. The user was able to see on the LCD display screen the real time
temperature of the system. To test the high setpoint, the user increased the temperature. Once the
temperature reached 87°F the buzzer sounded. To test the low setpoint, the user decreased the
temperature. Once the temperature reached 44°F the buzzer sounded.
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[Design Considerations]
8.0
Design Considerations
8.1
Assembly and Disassembly
Fall
2009
Designing a presentable fixture to encase and display the prototype was necessary for the setup
to look attractive. Once all the components had been selected, a determination of how much
volume the entire system would take was established and a fixture was reverse engineered
around the system components. Laminate wood composite was used to construct what would be
the main display panel, holding the different sections of wood laminate together were thin
rectangular beams of pine wood that can be seen in Figure 70. Preliminary sketches were
generated and the most aesthetic design was chosen. Using the machines and hand tools
Figure 69: Front Panel Construction
available to students in the FIU machine shop, the construction began. A rectangle was cut out
using a power drill and a jig-saw as seen in Figure 69, and a half inch hole was drilled. The
rectangle and half inch hole were cut out to accommodate the wiring of the control panel and the
pipe of the shower head, respectively. Once this was complete the board was spray painted grey
which provided a nice contrast with the anodized blue control panel and the chrome shower
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2009
head. To erect the front panel, the wooden rods were machined using a band saw with 45 degree
angled cuts, measured using a ruler, on both ends and two holes were drilled to facilitate the
insertion of the screws. Figure 73 shows the semi constructed panel.
Figure 70: Machining Wood Beams
Once the display had been erected, a bottom panel was attached to the other end of the wooden
beams. This provided a space for the water tanks and, in turn, acted as counter weight to the front
panel which was holding most of the electrical and some of the hydraulic components. As the
frame of the display panel was completed, mounting of the flow and temperature control valves
with their respective motors could begin. Again, a reverse engineering approach was taken to
design how the motors would be fixed to the wooden beams that would provide a reaction
torque. This reaction torque was necessary to prevent the stepper motors to spin freely. Knowing
that the maximum torque the motor could output, the design was restricted to this value. Since
the stepper motors supplied a relatively low amount torque, the design of the system that could
withstand the torque did not require materials of high yield strength.
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Figure 71: Complete Motor and Valve Assembly
Figure 72: Semi-Constructed Display Stand
Support for the motor attached to the mixing valve was provided by the beam traversing the top
section of the front display panel. Using a bendable piece of sheet metal, the motor was fixed to
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the wooden beam. The same method was applied to the motor that controlled the flow intensity
valve. This can be seen in Figure 74, and the entire motor and valve support assembly can be
seen in Figure 75.
Figure 73 : Fixed Motor on Mixing Valve
Figure 74 : Motor and Valve Support Assembly
Having a system including both electrical and hydraulic components, it was decided that a
protective compartment should be made to enclose the Board of Education, BiStep2A and
electrical circuits. Said enclosure was designed to be small, conveniently fit alongside the
remaining system components and provide protection from any possible water leaks. The same
type of material used to construct the display panel was used to assemble the small compartment.
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After the breadboards were measured, a bandsaw was used to cut the box’s sides to meet the
dimensions needed and all the sides were held together using metal plates bended at 90 degrees.
Figure 75 : Assembled Electrical Compartment
Once the this all assemblies were mounted, it was possible to position the remaining system
components including the control panel, the electrical box and water tanks into the most
convenient locations. Trying to maintain water and electrical system separate, it was decided that
the shower head should not be directly on top of the electrical control panel.
Figure 76 : Electrical Components in Compartment
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As seen in Figure 77, the shower head is mounted on the right side of its electrical elements. Not
only did this prevent the LCD screen and sensors from being splashed with water, it also allowed
the wiring behind the panel to be on opposite sides of the water hoses and valves.
The overall presentation of the prototype proves to be a compact system designed knowing that
electrical components are being used alongside water hoses, tanks and valves. The most difficult
hurdle in the design of the prototype assembly was fixing the motors so that they would not spin
freely. This required precise measurements and cuts at various lengths and angles that proved to
be time consuming. After taking all design alternatives and comparing them, the chosen one was
the design that would provide a safe, efficient and aesthetic appeal which was described and
shown in this section of the report.
Figure 77 : Complete Prototype Assembly
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8.2
Fall
2009
Regular Maintenance of the System
Components of the system that could require regular maintenance can be mostly found on the
parts that provide connections from one part to another, (i.e., fittings, joints, sealants). Here is
where a regular leak is most common found. A preventive maintenance plan should be followed
through to avoid water leaks as this would prove to be disastrous for the electrical parts of the
system.
Fittings should be checked and tightened regularly. It should be observed that all NPT joints are
wrapped with teflon tape prior to being tightened and sealant should be used in areas where there
seems to be a fracture in the fluid system. Obviously sealant would only provide a temporary
solution and major maintenance should be considered. Regular maintenance also includes
replacing old o-rings and hoses, applying grease to the valve knobs in order to reduce friction
that could cause the motors to work harder than they should.
Applying this preventive maintenance procedure, the digitally controlled shower should function
flawlessly over an extended period of time.
8.3
Major Maintenance of the System
Every system requires regular maintenance in order for it to perform at its maximum efficiency,
failure to do so can lead to further problems that require a major maintenance. This system is no
exception, failure to check hoses, valves and fitting for leaks can cause electronic components to
be exposed to water and permanently damage these costly items. If not properly grounded,
sudden power surges could cause the circuitry to experience a short circuit. This would most
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probably by the worse case as the electric parts of the system are the most costly and are more
difficult to set up than the hydraulic fittings, valves and hoses.
Leaking water can also cause the materials behind the walls to rot, this can greatly weaken the
structural components, if this were the case, an overhaul of the interior should be considered as
the mold can spread out to other areas behind the shower. Overall, the most important issue,
pertaining to maintenance, is to maintain a system free of any type of leakage.
Figure 78: Pneumatic and Hydraulic System Assembly
Figure 79 : Behind the Prototype
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8.4
Fall
2009
Environmental Impact
The present environment impact the digitally controlled shower system has, can be considered
low. This system does not replace the shower, but enhances the experience and provides a luxury
to those interested in such devices. That being said, measures can be taken within the scope of
the digitally controlled shower that could have a positive impact to the environment.
From an environmental perspective, this system has potential to be green engineered. For
example, as a design alternative, some buttons may be programmed to different presets. One of
these presets can be a “green shower”, where water temperature is brought below the usual
showing water temperature. This relieves the water heater of heating excessive amounts water
which in turn requires less electricity. Also, the “green shower” setting can be set to restrict the
waters flow rate to a minimum that is both environmentally friendly and enough water to take
good shower. A timer could be incorporated to the system and make the user conscious of how
much water is being used over the time that he/she may be showering.
8.5
Risk Assessment
As with most engineering designs, there is a degree of risk be it small or large, it should always
be considered. As mechanical engineers, this is viewed as the safety factor, and systems are
usually designed around this number. Fortunately, structural design was not the main design
criteria in the project, although there are other factors to be noticed. As mentioned before, this
system has both electrical and hydraulic components, if proper measures are not taken this can be
extremely dangerous to the user. Even though, the components operate at low voltages
appropriate precautions should be taken.
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All electrical sensors and buttons should be water proofed as these will be the components the
user will be in contact with. Electrical equipment behind the shower must also be protected from
any possible exposure to water as this may cause sparks and create a risk of fire. Also, some type
of fuse box should be considered for future design to act as a fail-safe.
Figure 80: Digitally Controlled Shower
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Team Aquemini:
9.0
Conclusion
9.1
Conclusion and Discussion
[Conclusion]
Fall
2009
The team’s project went through several design stages. These stages include changing certain
interface aspects. For example the older interface included the use of buttons to control the
operating functions of the shower. Upon further research, the group decided to implement the
use of infrared sensors as opposed to push buttons. Using these sensors the user can simply tap
his or her finger in the view of the sensor and permit the operating functions to take place (i.e.
increasing/decreasing) the temperature and the water flow. The group then decided to include a
power switch to turn on/off the system when not in operation, this way energy consumption can
be preserve and extend the life of the components.
Selection of the valves and motors was crucial in the design, since they are the key components
in the team’s design objective; to change an analog shower system into a digital system at a
reasonable price for the consumer. Selecting the valves revolved around only one constraint,
providing the user with precise control over the temperature and flow rate of the water. In the
original design of the system, the idea was to use two separate needle valves, one for the cold
and one hot water pipes. In the final design of the system it was decided that it would be more
efficient to implement a single mixing valve. Thus, the final design would eliminate the use of
two valves for both fluid delivery systems therefore making it cheaper to construct, since the new
design would eliminate the purchase of an extra motor to control the flow valve.
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[Conclusion]
Fall
2009
Using the two valves the team opted for, selection of the two motors could begin. To make sure
the correct motors were chosen, measurement of the amount of torque that would be needed to
actuate the valve pins needed to be noted. Using a torque wrench the measured value that the
motor would have output about 16 in-oz. This measurement along with the cost would be the
parameters in choosing the type of motors for the system. Upon researching the different motors
that were available on the market, it was suggested by the team’s advisor that stepper motors
would be the best type of motor to use for our application since the system needed accurate
control over its counterparts. The team was then directed to an online manufacturer of stepper
motors. With the design parameters in mind, a unipolar stepper motor with a torque of 1.32
kg•cm (18.33 in•oz) at a cost of $19.95 was chosen.
For the selection of the temperature sensor and LCD, the group decided to purchase the items
from the online robotics store, Parallax. The temperature sensor had to be purchased with another
component; an 8 bit analog to digital converter chip, because the sensor reads the temperature in
mV and the chip converts it into a digital signal. The liquid display was selected on the constraint
that the display had to be able to present two sets of data being measured one being the
temperature and the other being flow rate.
Another key component in the design of the prototype was choosing a stepper motor
microcontroller to operate both motors one at a time. The particular controller the group selected
at that time was the BiStep2A motor controller. This allowed operation any particular motor no
matter what the voltage requirements were, which would give the design more versatility in case
the motors the group selected could not actuate the valves pins at their current voltage ratings,
which may lead the group to select more powerful stepper motors. The manual that the vendor
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2009
provided for reference helped the team with the wiring and programming of the controller and
motors. Unfortunately, the controller had malfunctioned and another new controller had to be
ordered in its place. The team was able to get a good portion of the programming completed
before hardware failure occurred and the wiring is completely finished.
Once the motors and the microcontroller were obtained, the next step was to determine the
wiring sequence and prepare for the programming process. The manual that came with the motor
did not specify which color wire were the center taps, fortunately to identify these wires, the
“First Use” manual along with the advice from the vendor of the motor controller were
extremely helpful. By measuring the resistances between one particular wire against the other 5
wires, the group was able to locate 2 sets of 3 wires; one set belonging to winding A and the
other to winding B. If the wires were attached any other way to the terminals of the controller,
the board would have been severely damaged, although the group doesn’t not suspect this caused
hardware failure. Next, the amount of power that our components would need had to be
determined before deciding on a power supply. The voltage supply the project needed had to be a
minimum of 12 volts, but the amount of current would largely depend on the power requirements
of all our components. Take for example the two motors; by dividing the voltage supply over
their winding resistances (75 ohms) a value of .16 Amps is obtained. By following the suggested
multiplier factor provided in the first use manual, multiplying .16 and 2.5 giving us a current of
.40A for both motors simply multiply by 2 to obtain a value of 0.8A.
For the programming portion of the project, members of the team had previously obtained
another microcontroller from a previous course design project. The language used for controlling
the functions was PBASIC which is a very simple computer language to implement and is
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[Conclusion]
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2009
completely compatible with the motor controller. With this particular BS2 chip microcontroller
the device would be able to read the signal coming from the temperature sensor and display the
information on the LCD along with controlling the motor microcontroller.
The Prototype assembly was conceptualized through the use of sketches and Solidworks. The
team purchased and commissioned the construction materials and the machining services of the
machine shop available to students on site at Florida International University. The purchase of
two 1 gallon “Igloo” water coolers would be the tanks that would be pressurized and set to
deliver both the hot and cold fluids, through the use of a pressure gauge. Earlier in the project’s
concept stage the group had decided to use an C02 air tank to provide pressure to the two
coolers, but due to the size of the tank, it’s limited capacity and the needs of the design
application the tank would not be able to last us long enough to keep the system fully operable
for presentation purposes. Upon further consideration the team decided that use of the machine
shop’s pressurized air supply would better suite our application. Screw on bulk head fittings
were purchased to connect the plastic tubing from the coolers to the inlet pipes of the mixing
valve and from the outlet of the mixing valve to the inlet of the flow valve as seen in the figures
in the prototype assembly section. The next stage of assembly was to combine all of the
components together to form one assembly of the entire system. Laminate plywood was used to
build the “skeleton” for the assembly and mount the control panel onto the square shaped
wooden beams previously shown in the assembly section of this report.
Overall the project has progressed as smooth as the team expected, minus a few setbacks in the
case of faulty electrical equipment. As deadlines approached, difficult decisions were made
regarding the purchases of replacement equipment including the stepper motor controller
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[Conclusion]
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2009
BiStep2A and the LCD. These hurdles were overcome as required and a final working prototype
has been produced before the given deadlines. Besides the hurdles and the inconveniences the
team is happy with the final design of the prototype.
9.2
Patent/Copyright Application
Currently the team has no intention of filing g a patent application, since the group is designing a
low cost system and provides no other unique function. Although the team suspects that if given
the opportunity to further develop the system with a much larger budget, unique applications and
operations can be conceptualized and implemented into the current system. Perhaps from further
research into the design specifications of similar systems, one can build a more unique cost
effective product with the same if not better features then what others have to offer.
9.3
Commercialization Prospects of the Product
The team’s project has met the design objectives originally put forth. The design includes simple
to use features that will introduce a low cost product into the market and hopefully prompt
median income home owners who want to experience a moderately convenient upscale shower
system to purchase such a system. The system is meant to provide consumers with a low cost
alternative to the type of luxury shower systems that are readily available in the market.
Our goal is to market this product to a broad user base, current systems that exist in today’s
market simply tailor to high end home owners, so the product itself is a high end user device.
Approaching this with a business-like mind set, the priority would have to be to tailor our system
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Team Aquemini:
[Conclusion]
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2009
to the middle class, a group who don’t want to pay for an expensive system that would over
burden them with future maintenance cost. This cost constraint was kept in mind as the group
conceptualized and further developed their design. Another aspect that might turn off potential
buyers is the system involving too many functions and different interfaces that it may confuse
the user and might not motivate the user to ever use a particular feature at all. Our design focuses
on a simple user interface with two functions that would be preferable to the user.
The system would come packaged as a kit that any mechanically inclined individual can easily
install it him or herself, if a plumber was needed the labor and installation fees would be low due
to of the simple design of the system.
9.4
Future Work
Like all designs there is always room for optimization, especially in the group’s current project.
Given the limited budget, the group wasn’t given the full opportunity to explore any unique
function’s that could have been implemented in the conceptual design of the system. Earlier in
the design process the group discussed including a system where each member of the household
can preset their own temperature and flow rate of the shower, so when they entered the shower
just one push of a button would deliver their shower preferences. Creating a easy to carry
portable shower was an idea the group thought about for a while during this design project, and
the idea is could very well be applied to what the group has accomplished. The group also
brainstormed on employing a device that would be integrated with the actual tub that would be
able to massage the body while the user lay down while enjoying a nice bath. Further research
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Team Aquemini:
[Conclusion]
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2009
would have to be made on developing and implementing such a system and could add a large
cost, but such a system would probably be available only as an option for customers.
Furthermore, another system that would be compatible with our current design can be provided;
the system’s purpose would be to produce steam or mist that would provide the user with the
feeling of being in a sauna. Other products on the market offer functions such as mood lighting
or audio options, though those functions might be nice to have, the group does not feel that a
customer would not get a lot value from such operations. The team wants to provide realistic
functions that the user can get the maximum enjoyment out of at a reasonable price.
122
Team Aquemini:
[Appendices]
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10.0 References
1. Parallax Inc. “LM34 Temperature Sensor”. Parallax Inc. 2009. 9 March 2009.
http://www.parallax.com/Store/Sensors/TemperatureHumidity/tabid/174/CategoryID/49/List/
0/Level/a/ProductID/87/Default.aspx?SortField=ProductName%2cProductName
2. Stonybrook University. “Bragg's Law and Diffraction: How waves reveal the atomic
structure of crystals”. Parallax Inc. 2009. 9 March 2009.
http://www.eserc.stonybrook.edu/ProjectJava/Bragg/`
3. Norberg, Peter. “First Use”. Peter Norberg Consulting, Inc. 2002-2008.Web. 21 June 2009.
http://www.stepperboard.com/Downloads.htm
4. Norberg, Peter. “AppNotePNC001Parallax Quick Start”. Peter Norberg Consulting Inc.
2006. Web. 14 February 2008. http://www.stepperboard.com/Downloads.htm
5. Sinotech Shanghai. “Jameco Part Number 172646”. Jameco Electronics. 2009. Web. 16
September 2009. http://www.jameco.com/Jameco/Products/ProdDS/172646.pdf
6. Parallax Inc. “QTI Line Follower AppKit-v2.0”. Parallax Inc. 2009. Web. March 2009.
http://www.parallax.com/Store/Robots/AllRobots/tabid/755/CategoryID/51/List/0/Level/a/Pr
oductID/77/Default.aspx?SortField=ProductName%2cProductName
7. Globalvillageidiot. “Microcontroller”. Web. 6 April 2006.
http://www.globalvillageidiot.info/grey/archives/00000006.htm
8. Gostar. “Needle Valve”. Gostar. 2008. Web. 21 August
2009.http://www.gostarcn.com/product_detail.asp?id=272
9. Jones, Douglas W. “Stepping Motor Types” Control of Stepper Motors: A tutorial. 1995.
Web. n.pag. 1998. http://www.cs.uiowa.edu/~jones/step/index.html
123
Team Aquemini:
[Appendices]
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2009
10. Peiró, Salvador Torres. , Antonio Díez, José Luis Cruz, and Miguel Vicente Andrés.
“Temperature Sensor Based on Ge-Doped Microstructured Fibers.” Journal of Sensors
Vol.2009. Web. 2009. http://www.hindawi.com/journals/js/2009/417540.html
11. Paschotta, Dr. Rüdiger. “Fiber Bragg Gratings”. Encyclopedia of Laser Physics and
Technology. 2009. Web. 11 March 2009. http://www.rpphotonics.com/fiber_bragg_gratings.html
12. L. Jin, W. Zhang, H. Zhang, et al., “An embedded FBG sensor for simultaneous
measurement of stress and temperature,” IEEE Photonics Technology Letters, vol. 18, no. 1,
pp. 154–156, 2006.
13. S. K. A. K. Bey, T. Sun, and K. T. V. Grattan, “Optimization of a long-period grating-based
Mach-Zehnder interferometer for temperature measurement,” Optics Communications, vol.
272, no. 1, pp. 15–21, 2007
14. S. Torres-Peiró, A. Díez, J. L. Cruz, and M. V. Andrés, “Fundamental-mode cutoff in liquidfilled Y-shaped microstructured fibers with Ge-doped core,” Optics Letters, vol. 33, no. 22,
pp. 2578–2580, 2008.
15. Y. J. Rao, “In-fiber Bragg grating sensors,” Measurement Science and Technology, vol. 8,
no. 4, pp. 355–375, 1997.
16. Moen. “Chrome ioDigital Shower Only””. 2009. Web. 9 November 2009.
http://www.moen.com/ecatalog/detail/moen/chrome-iodigital-tm-shower-only/_/RCONSUMER%3AT3405
17. Kohler. “DTV Custom Shower Experience”. 2009. Web. 9 November 2009.
http://www.us.kohler.com/performanceshowers/dtv.jsp
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Team Aquemini:
[Appendices]
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18. Jameco. “MOTOR,STEP,12VDC/30 ohm,”. 2009. Web. 9 November 2009.
http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=1&storeId=10001&catalogId=10001&productId=155460
19. Parallax Inc. “Board of Education”. Parallax Inc. 2009. Web. November 2009.
http://www.parallax.com/Store/Microcontrollers/BASICStampDevelopmentBoards/tabid/137
/CategoryID/12/List/0/SortField/0/Level/a/ProductID/125/Default.aspx
20. Norberg, Peter. “BiStep2A Serial Board”. Peter Norberg Consulting, Inc. 2002-2008.Web.
21 June 2009. http://www.stepperboard.com/AssembledBiStep2A.htm
21. Parallax Inc. “8 Bit A\D Converter”. Parallax Inc. 2009. Web. November 2009.
http://www.parallax.com/Store/Microcontrollers/BASICStampDevelopmentBoards/tabid/137
/CategoryID/12/List/0/SortField/0/Level/a/ProductID/125/Default.aspx
22. Parallax Inc. “2x16 Backlit LCD”. Parallax Inc. 2009. Web. November 2009.
http://www.parallax.com/Store/Accessories/Displays/tabid/159/CategoryID/34/List/0/Level/a
/ProductID/50/Default.aspx?SortField=ProductName%2cProductName
23. Ultimate Paintball Gear “CO2 Canister”. Ultimate Paintball Gear . 2009. Web. November
2009. http://ultimatepaintballgear.biz/catalog/images/20oz_co2_tank.jpg
24. Ultimate Paintball Gear “Air Regulator”. Ultimate Paintball Gear . 2009. Web. November
2009. http://ultimatepaintballgear.biz/catalog/images/200psi_air_reg.jpg
25. Ultimate Paintball Gear “Pressure Gauge”. Ultimate Paintball Gear . 2009. Web. November
2009. http://ultimatepaintballgear.biz/catalog/images/prssure_guage.jpg
26. Sideways Technologies “Flared JIC”. Sideways Technologies . 2009. Web. November
2009. http://www.sideways-technologies.co.uk/images/pipedia.gif
125
Team Aquemini:
[Appendices]
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27. Sideways Technologies “Flared SAE”. Sideways Technologies . 2009. Web. November
2009. http://www.sideways-technologies.co.uk/images/pipedia.gif
28. Raising Children. “Bath Temperature: Raising Temperature Network”. 2009. Web. 9
November 2009. http://raisingchildren.net.au/articles/safe_water_temperature.html
29. AliBaba.com. “NPT to Male JIC Fitting”. 2009. Web. 9 November 2009.
http://img.alibaba.com/photo/222150136/male_fitting.summ.jpg
30. AliBaba.com. “Push on Barb Fittings”. 2009. Web. 9 November 2009.
31. AliBaba.com. “Bulkhead Fitting”. 2009. Web. 9 November 2009.
32. AliBaba.com. “Needle Valve Detail”. 2009. Web. 9 November 2009.
http://img.alibaba.com/photo/11826787/Needle_Valve.jpg
33. PlumbingHelp.ca “Example of Mixer Valve”. 2009. Web. November 2009.
http://www.plumbinghelp.ca/images/mixing%20valve%20operation.JPG
34. Incropera, Frank P and David P. DeWitt. Fundamentals of Heat and Mass Transfer.
4th Edition, John Wiley & Sons, NY 1996.
35. Grainger "Pneumatic System Components: Industrial Supply Catalogue." International
(2007): pg 3308. Print.
36. Radio Shack. “Project Power Supply”. Enercell™ Multivoltage 2.5A AC Power Adapter.
2009. Web. November 2009.
http://www.radioshack.com/product/index.jsp?productId=3832487
126

Digitally Controlled Shower, Alberto Garcia, Lorenzo Green

Transcription

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