speed control of stepper motor by using ucn5804b translator

Transcription

SPEED CONTROL OF STEPPER MOTOR USING UCN5804B TRANSLATOR
SPEED CONTROL OF STEPPER MOTOR
BY
USING UCN5804B TRANSLATOR
PRAKASAM ENGINEERING COLLEGE
I
Contents
INTRODUCTION.............................................................................................................................. 1
CIRCUIT DESCRIPTION.................................................................................................................... 3
ASSEMBLY INSTRUCTIONS............................................................................................................. 6
PARTS LIST FOR THE STEPPER MOTOR CONTROL........................................................................ 11
STEPPER MOTOR.......................................................................................................................... 14
UCN5804 STEPPER-MOTOR TRANSLATOR/DRIVER...................................................................... 28
555 Timer..................................................................................................................................... 41
VOLTAGE REGULATOR................................................................................................................. 62
LED............................................................................................................................................... 80
OPERATION OF STEPPER MOTOR USING UCN5804B TRANSLATOR............................................. 86
APPLICATIONS:............................................................................................................................. 89
HARDWARE COMPONENTS .................................................................................. 91
II
ASSEMBLY INSTRUCTIONS
The easiest way to build the stepper motor controller is to use an etched circuit
board as shown in Figure 2. If you don’t want to fabricate your own board, a pre-etched
and drilled board Can be purchased from the source shown in the parts list.
III
IV
Fig.2
Locate all the components shown in the parts list and use
Figure 3 to determine component placement on the PC board.
Begin by using three pieces of solid wire for J1, J2, and J3.Next install and
solder the four diodes in place, noting their polarity. Then move on to the resistors and
ceramic capacitors.
When installing the 5-watt resistors R1 and R2, leave a small space between
the resistors and the PC board to allow for air circulation. Be sure to observe proper
polarities when installing
The electrolytic and tantalum capacitors and the voltage regulator. Note
that it may be necessary to bend the leads of the U4 to fit the PC board.
Now solder IC sockets for U1, U2, and U3 to the board. If you use the
switch specified in the parts list for S5, it can be soldered directly on the printed circuit
board. Then install the four LEDs as shown in Figure 3.
V
Fig.3
It is recommended that you use screw-terminal connectors for P1 andP2.
Potentiometer R13 can be either PC mount style or panel mount style. To use a panel
mount potentiometer, cut three pieces of stranded wire to connect R3 to the PC board. If
you plan to use the controller in standalone mode, solder a four-position DIP witch for
S1-4. You may omit the DIP switch if you plan to use the P3 connector for remote
interfacing. Next, locate the UCN5804B integrated circuit (U1). Since U1 is a CMOS
device, it can be easily damaged by static electricity. Take proper anti-static precautions
when handling the chip. Refer again to Figure 3 before installing U1 to make sure of the
proper orientation of pin 1, then press the IC firmly into the 16-pin socket. Repeat the
procedure with ICs U2 and U3
ASSEMBLY
Before continuing, clean the foil side of the PC board with alcohol or flux
remover. Then refer to Figure 4 for details on connecting the stepper motor and DC
power supply. Note that the wire colors for the stepper motor shown in Figure 4 apply
only to the PF-42 motor that is included in the purchased kit. If you usea different motor,
VI
you will need to determine the appropriate wire connections to P2. Also note that the
circuit is designed to drive six-wire UNIPOLAR motors only. Next, attach the wires
from the DC power source to the PC ard,observing the polarity show in Figure 4.
VII
PARTS LIST FOR THE STEPPER MOTOR CONTROL
 STEPPER MOTOR
 SEMI CONDUCTORS
o U1 ........... UCN5804B, Stepper Controller IC
o U2,3 ......... LM555N, Timer IC
o U4 ........... LM78L05, 5 Volt DC Regulator (TO92)
o D1-4.......... 1N4001 (or 1N4004), Rectifier Diode
o L1-4 ......... RED Light Emitting Diode

Resistors (Except where noted, resistors are 5%, 1/4 Watt)
o R1,2 ....... 50 Ohm, 5 Watt
o R3 ........ 330 Ohm (Orange, Orange, Brown, Gold)
o R4 ........ 10 K Ohm (Brown, Black, Orange, Gold)
o R5 ........ 22 K Ohm (Red, Red, Orange, Gold)
o R6 ........ 220 K Ohm (Red, Red, Yellow, Gold)
o R7-12 ..... 100 K Ohm (Brown, Black, Yellow,
Gold)
o R13 ....... 100 K Ohm Potentiometer
o Capacitors
o C1-3 ......... 0.1 uF, Ceramic, marked: [104]
o C4-6 .......... 1.0 uF, 16V Tantalum or Electrolytic
o C7 ........... 470 uF, 35V Electrolytic
o Miscellaneous Items
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
JP1 — Wire Jumper, 0.4 inches long



J1 — 3-pin Jumper Post & Shorting Blocks

J2 — 2-pin Jumper Post & Shorting Blocks

P1 — 2-pos Terminal Block

P2 — 6-pos Terminal Block

P3 — 7-pin Jumper Post

S1-4 — 4-position DIP Switch

S5 — Miniature Pushbutton Switch

U1 — 16-Pin IC Socket

U2,3 — 8-Pin IC Socket

PCB — Etched Printed Circuit Board
(STP0297)

MOT — Unipolar (6-wire) Stepper Motor

TXFMR — 12-14V DC, 500mA Wall
Transformer or DC power supply
•
Misc: Hook-up Wire, Hardware, Solder,
Etc.
IX
STEPPER MOTOR
INTRODUCTION
Motion Control, in electronic terms, means to accurately control the movement
of an object based on either speed, distance, load, inertia or a combination of all these
factors. There are numerous types of motion control systems, including; Stepper Motor,
Linear Step Motor, DC Brush, Brushless, Servo, Brushless Servo and more. This
document will concentrate on Step Motor technology.
In Theory, a Stepper motor is a marvel in simplicity. It has no brushes,
or contacts. Basically it's a synchronous motor with the magnetic field electronically
switched to rotate the armature magnet around.
A Stepping Motor System consists of three basic elements, often combined with some
type of user interface
The Indexer (or Controller) is a microprocessor capable of
generating step pulses and direction signals for the driver. In addition, the
indexer is typically required to perform many other sophisticated command
functions.
Example Indexer: IBC-400
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The Driver (or Amplifier) converts the indexer
command signals into the power necessary to energize the motor windings.
There are numerous types of drivers, with different current/amperage ratings
and construction technology. Not all drivers are suitable to run all motors, so
when designing a Motion Control System the driver selection process is
critical.
Example Driver: DR-38M
The Step Motor is an electromagnetic device that converts digital pulses into
mechanical shaft rotation. Advantages of step motors are low cost, high reliability, high
torque at low speeds and a simple, rugged construction that operates in almost any
environment. The main disadvantages in using a step motor is the resonance effect often
exhibited at low speeds and decreasing torque with increasing speed.
Example Step Motors: AM Series
TYPES OF STEPPER MOTORS
There are basically three types of stepping motors; variable reluctance,
permanent magnet and hybrid. They differ in terms of construction based on the use of
permanent magnets and/or iron rotors with laminated steel stators.
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VARIABLE RELUCTANCE
The variable reluctance motor does not use a permanent magnet. As a result,
the motor rotor can move without constraint or "detent" torque. This type of construction
is good in non industrial applications that do not require a high degree of motor torque,
such as the positioning of a micro slide.
The variable reluctance motor in the above illustration has four
"stator pole sets" (A, B, C,), set 15 degrees apart. Current applied to pole A through the
motor winding causes a magnetic attraction that aligns the rotor (tooth) to pole A.
Energizing stator pole B causes the rotor to rotate 15 degrees in alignment with pole B.
This process will continue with pole C and back to A in a clockwise direction. Reversing
the procedure (C to A) would result in a counter clockwise rotation.
PERMANENT MAGNET
The permanent magnet motor, also referred to as a "canstack" motor, has, as the
name implies, a permanent magnet rotor. It is a relatively low speed, low torque device
with large step angles of either 45 or 90 degrees. It's simple construction and low cost
make it an ideal choice for non industrial applications, such as a line printer print wheel
positioner.
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Unlike the other stepping motors, the PM motor rotor has no teeth and is
designed to be magnetized at a right angle to it's axis. The above illustration shows a
simple, 90 degree PM motor with four phases (A-D). Applying current to each phase in
sequence will cause the rotor to rotate by adjusting to the changing magnetic fields.
Although it operates at fairly low speed the PM motor has a relatively high torque
characteristic.
HYBRID
Hybrid motors combine the best characteristics of the variable reluctance and
permanent magnet motors. They are constructed with multi-toothed stator poles and a
permanent magnet rotor. Standard hybrid motors have 200 rotor teeth and rotate at 1.80
step angles. Other hybrid motors are available in 0.9ºand 3.6º step angle configurations.
Because they exhibit high static and dynamic torque and run at very high step rates,
hybrid motors are used in a wide variety of industrial applications.
MOTOR WINDINGS
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UNIFILAR
Unifilar, as the name implies, has only one winding per stator pole. Stepper
motors with a unifilar winding will have 4 lead wires. The following wiring diagram
illustrates a typical unifilar motor:
BIFILAR
Bifilar wound motors means that there are two identical sets of windings on
each stator pole. This type of winding configuration simplifies operation in that
transferring current from one coil to another one, wound in the opposite direction, will
reverse the rotation of the motor shaft. Whereas, in a unifilar application, to change
direction requires reversing the current in the same winding.
The most common wiring configuration for bifilar wound stepping motors is 8
leads because they offer the flexibility of either a Series or parallel connection. There are
however, many 6 lead stepping motors available for Series connection applications.
STEP MODES
Stepper motor "step modes" include Full, Half and Micro step. The type of step mode
output of any motor is dependent on the design of the driver.
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FULL STEP
Standard (hybrid) stepping motors have 200 rotor teeth, or 200 full steps per
revolution of the motor shaft. Dividing the 200 steps into the 360º's rotation equals a 1.8º
full step angle. Normally, full step mode is achieved by energizing both windings while
reversing the current alternately. Essentially one digital input from the driver is
equivalent to one step.
HALF STEP
Half step simply means that the motor is rotating at 400 steps per revolution. In
this mode, one winding is energized and then two windings are energized alternately,
causing the rotor to rotate at half the distance, or 0.9º's. (The same effect can be achieved
by operating in full step mode with a 400 step per revolution motor). Half stepping is a
more practical solution however, in industrial applications. Although it provides slightly
less torque, half step mode reduces the amount "jumpiness" inherent in running in a full
step mode.
MICROSTEP:
Micro stepping is a relatively new stepper motor technology that controls the
current in the motor winding to a degree that further subdivides the number of positions
between poles. AMS micro step drives are capable of rotating at 1/256 of a step (per
step), or over 50,000 steps per revolution.
Micro stepping is typically used in applications that require accurate positioning and a
fine resolution over a wide range of speeds.
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MAX-410/MAX-420 micro step drives integrate state-of-the-art hardware with "VRMC"
(Variable Resolution Micro step Control) technology developed by AMS. At slow shaft
speeds, VRMCs produces high resolution micro step positioning for silent, resonancefree operation. As shaft speed increases, the output step resolution is expanded using
"on-motor-pole" synchronization. At the completion of a coarse index, the target micro
position is trimmed to 1/100 of a (command) step to achieve and maintain precise
positioning.
MAX-410 and MAX-420 with VRMC.
DESIGN CONSIDERATIONS
The electrical compatibility between the motor and the driver are the most
critical factors in a stepper motor system design. Some general guidelines in the selection
of these components are:
INDUCTANCE
Stepper motors are rated with a varying degree of inductance. A high
inductance motor will provide a greater amount of torque at low speeds and similarly the
reverse is true.
SERIES, PARALLEL CONNECTION
There are two ways to connect a stepper motor; in series or in parallel. A
series connection provides a high inductance and therefore greater performance at low
speeds. A parallel connection will lower the inductance but increase the torque at faster
speeds. The following is a typical speed/torque curve for an AMS driver and motor
connected in series and parallel:
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DRIVER VOLTAGE
The higher the output voltage from the driver, the higher the level of torque vs.
speed. Generally, the driver output voltage should be rated higher than the motor voltage
rating.
MOTOR STIFFNESS
By design, stepping motors tend to run stiff. Reducing the current flow to the
motor by a small percentage will smooth the rotation. Likewise, increasing the motor
current will increase the stiffness but will also provide more torque. Trade-offs between
speed, torque and resolution are a main consideration in designing a step motor system.
MOTOR HEAT
Step motors are designed to run hot (50º-90º C). However, too much current may
cause excessive heating and damage to the motor insulation and windings. AMS step
motor products reduce the risk of overheating by providing a programmable Run/Hold
current feature.
DRIVER TECHNOLOGY OVERVIEW
The stepper motor driver receives low-level signals from the indexer or control
system and converts them into electrical (step) pulses to run the motor. One step pulse is
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required for every step of the motor shaft. In full step mode, with a standard 200 step
motor, 200 step pulses are required to complete one revolution. Likewise, in micro
stepping mode the driver may be required to generate 50,000 or more step pulses per
revolution.
In standard driver designs this usually requires a lot of expensive circuitry. (AMS is able
to provide equal performance at low cost through a technology developed at AMS
known as VRMC®; Variable Resolution Micro step Control).
Speed and torque performance of the step motor is based on the flow of current from the
driver to the motor winding. The factor that inhibits the flow, or limits the time it takes
for the current to energize the winding, is known as inductance. The lower the
inductance, the faster the current gets to the winding and the better the performance of
the motor. To reduce inductance, most types of driver circuits are designed to supply a
greater amount of voltage than the motors rated voltage.
TYPES OF STEPPER MOTOR DRIVERS
For industrial applications there are basically three types of driver technologies. They all
utilize a "translator" to convert the step and direction signals from the indexer into
electrical pulses to the motor. The essential difference is in the way they energize the
motor winding. The circuit that performs this task is known as the "switch set."
UNIPOLAR
The name unipolar is derived from the fact that current flow is limited to one
direction. As such, the switch set of a unipolar drive is fairly simple and inexpensive.
XVIII
The drawback to using a unipolar drive however, is it's limited capability to energize all
the windings at any one time. As a result, the number of amp turns (torque) is reduced by
nearly 40% compared to other driver technologies. Unipolar drivers are good for
applications that operate at relatively low step rates.
R/L
R/L (resistance/limited) drivers are, by today's standards, old technology but
still exist in some (low power) applications because they are simple and inexpensive.
The drawback to using R/L drivers is that they rely on a "dropping resistor" to get almost
10 times the amount of motor current rating necessary to maintain a useful increase in
speed. This process also produces an excessive amount of heat and must rely on a DC
power supply for it's current source.
BIPOLAR CHOPPER
Bipolar chopper drivers are by far the most widely used drivers for industrial
applications. Although they are typically more expensive to design, they offer high
performance and high efficiency. Bipolar chopper drivers use an extra set of switching
transistors to eliminate the need for two power sources. Additionally, these drivers use a
four transistor bridge with recirculating diodes and a sense resistor that maintains a
feedback voltage proportional to the motor current. Motor windings, using a bipolar
chopper driver, are energized to the full supply level by turning on one set (top and
bottom) of the switching transistors. The sense resistor monitors the linear rise in current
until the required level is reached. At this point the top switch opens and the current in
the motor coil is maintained via the bottom switch and the diode. Current "decay" (lose
over time) occurs until a preset position is reached and the process starts over. This
"chopping" effect of the supply is what maintains the correct current voltage to the motor
at all times.
XIX
Example: Chopper Drives with built-in Power Supply
INDEXER OVERVIEW
The indexer, or controller, provides step and direction outputs to the driver. Most
applications require that the indexer manage other control functions as well, including
acceleration, deceleration, steps per second and distance. The indexer can also interface
to and control, many other external signals.
Microprocessor based indexers offer a great deal of flexibility in that they can operate in
either stand-alone mode or interfaced to a host computer. The following illustration
highlights the elements of a typical AMS indexer:
XX
Example: Indexer SMC-40
Communication to the indexer is either Bus-based or through an RS-232/
RS-422 serial port. In either case, the indexer is capable of receiving high level
commands from a host computer and generating the necessary step and direction pulses
to the driver. The indexer includes an auxiliary I/O for monitoring inputs from external
sources such as a Go, Jog, Home or Limit switch. It can also initiate other machine
functions through the I/O output pins.
STAND-ALONE OPERATION
In a stand-alone mode the indexer can operate independent of the host
computer. Once downloaded to the non-volatile memory motion programs can be
initiated from various types of operator interfaces, such as a keypad or switch, or through
the auxiliary I/O inputs. A stand-alone stepper motor control system is often packaged
with a driver and/or power supply and optional encoder feedback for "closed loop"
applications that require stall detection and exact motor position compensation.
XXI
INTEGRATEDCONTROL
Integrated control means the indexer is embedded within the complete system
and accepts commands from the host computer "on-line" throughout the entire motion
process. Communication, operator interface and the I/O functions are designed as
separate elements of the system. Control and management of the motion sequence is
done by the host computer. In this case the indexer acts as an intelligent peripheral. CNC
(computer numerical control) applications are well suited for integrated control because
the data input is "dynamic", or changing frequently.
MULTI-AXIS CONTROL
Many motion applications have more than one motor to control. In such cases a
multi-axis control system is available. A PC Bus step motor controller card for example,
may have up to four indexers mounted on it; each one connected to a separate driver and
motor. In a serial communication mode, up to 32 axis can be controlled from a single
communication port and/or I/O channel.
XXII
Example: Muli-axis Control: DAX
Some applications require a high degree of synchronization, such as circular or linear
interpolation. Here, it may be necessary to coordinate the movement with a central
processor. AMS provides a variety of single board or modular level controllers for these
types of operations
UCN5804 STEPPER-MOTOR TRANSLATOR/DRIVER
INTRODUCTION:
Combining low-power CMOS logic with high-current and high-voltage
bipolar outputs, the UCN5804B and UCN5804LB BiMOS II translator/ drivers provide
complete control and drive for a four-phase unipolar stepper motor with continuous
output current ratings to 1.25 A per phase (1.5 Astartup) and 35 V.
XXIII
The CMOS logic section provides the sequencing logic, DIRECTION and
OUTPUT ENABLE control, and a power-on reset function. Three stepper-motor drive
formats, wave-drive (one-phase), two-phase, and half step are externally selectable. The
inputs are compatible with standard CMOS, PMOS, and NMOS circuits. TTL or LSTTL
may require the use of appropriate pull-up resistors to ensure a proper input-logic high.
The wave-drive format consists of energizing one motor phase at a time
in an A-B-C-D (or D-C-B-A) sequence.
This excitation mode consumes the least power and assures
positional accuracy regardless of any winding In balance in the motor. Two-phase drive
energizes two adjacent phases in each detent position (AB-BC-CD-DA).
This sequence mode offers an improved torque-speed product, greater detent
torque, and is less susceptible to motor resonance. Half-step excitation alternates
between the one-phase and two-phase modes (A-AB-B-BC-C-CD-D-DA), providing an
eight-step sequence.
The bipolar outputs are capable of sinking up to 1.5 A and withstanding
50 V in the off state (sustaining voltages up to 35 V). Ground-clamp and fly back diodes
XXIV
provide protection against inductive transients. Thermal protection circuitry disables the
outputs when the chip temperature is excessive.
Both devices are rated for operation over the temperature range of -20°C
to +85°C. The UCN5804B is supplied in a 16-pin dual in-line plastic batwing package
with a copper lead frame and heat-sinkable tabs for improved power dissipation
capabilities; the UCN5804LB is supplied in a 16-lead plastic SOIC batwing package
with a copper lead frame and heat-sinkable tabs.
FEATURES
 1.5 A Maximum Output Current
 35 V Output Sustaining Voltage
 Wave-Drive, Two-Phase, and Half-Step Drive Formats
 Internal Clamp Diodes
 Output Enable and Direction Control
 Power-On Reset
 Internal Thermal Shutdown Circuitry
ABSOLUTE MAXIMUM RATINGS
•
Output Voltage, VCE ..........................................................50 V
•
Output Sustaining Voltage, VCE (suss) ......................................35 V
•
Output Sink Current, IOUT ................................................1.5 A
•
Logic Supply Voltage, VDD ...............................................7.0 V
•
Input Voltage, VIN ..............................................................7.0 V
•
Package Power Dissipation,
PD .............................................See Graph
•
Operating Temperature Range,
TA ..................................................-20°C to +85°C
•
Storage Temperature Range,
TS ................................................-55°C to +150°C
TYPICAL INPUT CIRCUIT
XXV
TYPICAL OUTPUT DRIVER
XXVI
Characterstics
XXVII
TRUTH TABLE
XXVIII
TIMING CONDITIONS
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A. Minimum Data Set Up Time . . . . . . . . . . . . . . . . . . . . . . . . 100 ns
B. Minimum Data Hold Time . . . . . . . . . . . . . . . . . . . . . . . . . . 100 ns
C. Minimum Step Input Pulse Width . . . . . . . . . . . . . . . . . . . . . 3.0
APPLICATIONS INFORMATION
Internal power-on reset (POR) circuitry resets OUTPUTA (and OUTPUTD
in the two-phase drive format) to the on state with initial application of the logic supply
voltage. After reset, the circuit then steps according to the tables.
WAVE- DRIVE SEQUENCE
XXX
The outputs will advance one sequence position on the high-to-low
transition of the STEP INPUT pulse. Logic levels on the HALF-STEP and ONE-PHASE
inputs will determine the drive format (one-phase, two-phase, or half-step). The
DIRECTION pin determines the rotation sequence of the outputs. Note that the STEP
INPUT must be in the low state when changing the state of ONE-PHASE, HALF-STEP,
or DIRECTION to prevent erroneous stepping.
TWO-PHASE DRIVE SEQUENCE
All outputs are disabled (off) when OUTPUT ENABLE is at a logic high. If
the function is not required, OUTPUT ENABLE should be tied low. In that condition, all
outputs depend only on the state of the step logic.
During normal commutation of a unipolar stepper motor, mutual coupling
between the motor windings can force the outputs of the UCN5804B below ground. This
condition will
cause forward biasing of the collector-to-substrate junction and source current from the
output.
For many L/R applications, this substrate current is high enough to
adversely affect the logic circuitry and cause misstepping. External series diodes
XXXI
(Schottky are recommended for increased efficiency at low-voltage operation) will
prevent substrate current from being sourced through the outputs. Alternatively, external
ground clamp diodes will provide a preferred current path from ground when the outputs
are pulled below ground.
HALF- STEP DRIVE SEQUENCE
Internal thermal protection circuitry disables all outputs when the junction
temperature reaches approximately 165C. The outputs are enabled again when the
junction cools down to approximately 145C.
XXXII
TYPICAL APPLICATION
L/R Stepper-Motor Drive
UCN5804B
Dimensions in Inches
(controlling dimensions)
XXXIII
XXXIV
Dimensions in Millimeters
(for reference only)
XXXV
555 Timer
General Description
The LM555 is a highly stable device for generating accurate time
delays or
oscillation. Additional terminals are provided for triggering or resetting if
desired. In the time delay mode of operation, the time is precisely controlled by one
external resistor and capacitor. For astable operation as an oscillator, the free running
frequency and duty cycle are accurately controlled with two external resistors and one
capacitor. The circuit may be triggered and reset on falling waveforms, and the output
circuit can source or sink up to 200mA or drive TTL circuits.
Features:
 Direct replacement for SE555/NE555
 Timing from microseconds through hours
 Operates in both stable and monostable modes
 Adjustable duty cycle
 Output can source or sink 200 mA
 Output and supply TTL compatible
 Temperature stability better than 0.005% per °C
 Normally on and normally off output
XXXVI
 Available in 8-pin MSOP package
Schematic Diagram:
XXXVII
Connection Diagram
Dual-In-Line, Small Outline and Molded Mini Small Outline
Packages
XXXVIII
Typical Performance Characteristics
Minimum Pulse Width
Supply Current vs. Supply Voltage
XXXIX
Required for Triggering
XL
High Output Voltage vs. Output
Low Output Voltage vs.
Output
Sink Current
Low Output Voltage vs.
vs.
Output Sink Current
Source Current
Low Output Voltage
Output Sink Current
XLI
Output Propagation Delay vs.
Delay vs Voltage Level of Trigger Pulse
Output Propagation
Voltage Level of
Trigger Pulse
Discharge Transistor (Pin 7)
oltage vs. Sink Current
Discharge Transistor
Voltage vs. Sink Current
XLII
Applications Information
MONOSTABLE OPERATION
In this mode of operation, the timer functions as a one-shot (Figure 1). The
external capacitor is initially held discharged by a transistor inside the timer. Upon
application of a negative trigger pulse of less than 1/3 VCC to pin 2, the flip-flop is set
which both releases the short circuit across the capacitor and drives the output high.
FIGURE 1. Monostable
XLIII
The voltage across the capacitor then increases exponentially for a period of t
= 1.1 RA C, at the end of which time the voltage equals 2/3 VCC. The comparator then
resets the flip-flop which in turn discharges the capacitor and drives the output to its low
state. Figure 2 shows the waveforms generated in this mode of operation. Since the
charge and the threshold level of the comparator are both directly proportional to supply
voltage, the timing interval is independent of supply.
VCC = 5V
TIME = 0.1 ms/DIV
RA = 9.1k∧
Top Trace: Input 5V/Div.
.
Middle Trace: Output 5V/Div.
Bottom Trace: Capacitor Voltage 2V/Div.
C = 0.01μF
FIGURE 2. Monostable Waveforms
During the timing cycle when the output is high, the further application of a
trigger pulse will not effect the circuit so long as the trigger input is returned high at least
10μs before the end of the timing interval. However the circuit can be reset during this
time by the application of a negative pulse to the reset terminal (pin 4). The output will
then remain in the low state until a trigger pulse is again applied. When the reset function
is not in use, it is recommended that it be connected to VCC to avoid any possibility of
false triggering.Figure 3 is a nomograph for easy determination of R, values for various
time delays.
XLIV
FIGURE 3. Time Delay
ASTABLE OPERATION
If the circuit is connected as shown in Figure 4 (pins 2 and
6connected) it will trigger itself and free run as a multivibrator. The external capacitor
charges through RA + RB and discharges through RB. Thus the duty cycle may be
precisely set by the ratio of these two resistors.
FIGURE 4. Astable
XLV
In this mode of operation, the capacitor charges and discharges between
1/3 VCC and 2/3 VCC. As in the triggered mode, the charge and discharge times, and
therefore the frequency are independent of the supply voltage.
Figure 5 shows the waveforms generated in this mode of operation.
VCC = 5V
Top Trace: Output 5V/Div.
TIME = 20μs/DIV.
Bottom Trace: Capacitor Voltage
1V/Div.
RA = 3.9k∧
RB = 3k∧
C = 0.01μF
FIGURE 5. Astable Waveforms
The charge time (output high) is given by:
t1 = 0.693 (RA + RB) C
And the discharge time (output low) by:
t2 = 0.693 (RB) C
Thus the total period is:
T = t1 + t2 = 0.693 (RA +2RB) C
XLVI
The frequency of oscillation is:
The duty cycle is:
Figure 6 may be used for quick determination of these RC values.
FIGURE 6. Free Running Frequency
FREQUENCY DIVIDER
The monostable circuit of Figure 1 can be used as a frequency divider by
adjusting the length of the timing cycle. Figure 7 shows the waveforms generated in a
divide by three circuit.
XLVII
VCC = 5V
TIME = 20μs/DIV.
RA = 9.1k∧
Bottom Trace: Capacitor 2V/Div.
C = 0.01μF
FIGURE 7. Frequency Divider
PULSE WIDTH MODULATOR
When the timer is connected in the monostable mode and triggered
with a continuous pulse train, the output pulse width can be modulated by a
signal applied to pin 5. Figure 8 shows the circuit, and in Figure 9 are some
waveform examples.
FIGURE 8. Pulse Width Modulator
XLVIII
VCC = 5V Top
TIME = 0.2 ms/DIV.
Trace: Modulation 1V/Div.
Bottom Trace: Output Voltage
2V/Div.
RA = 9.1k
C = 0.01μF
FIGURE 9. Pulse Width Modulator
PULSE POSITION MODULATOR
This application uses the timer connected for astable operation, as in
Figure 10, with a modulating signal again applied to the control voltage terminal. pulse
position varies with the modulating signal, since the threshold voltage and hence the time
delay is varied. Figure 11 shows the waveforms generated for a triangle wave
modulation signal.
XLIX
VCC = 5V
Top Trace: Modulation Input
1V/Div.
TIME = 0.1 ms/DIV.
Bottom Trace: Output 2V/Div.
RA = 3.9k
RB = 3k
C = 0.01μF
FIGURE 11. Pulse Position Modulator
L
LINEAR RAMP
When the pullup resistor, RA, in the monostable circuit is replaced by a
constant current source, a linear ramp is generated. Figure 12 shows a circuit
configuration that will perform this function.
FIGURE 12.
Figure 13 shows waveforms generated by the linear ramp.
The time interval is given by:
VBE = 0.6V
LI
VCC = 5V
TIME = 20μs/DIV.
R1 = 47kBottom Trace: Capacitor Voltage 1V/Div.
R2 = 100k
RE = 2.7 k
C = 0.01 μF
FIGURE 13. Linear Ramp
50% DUTY CYCLE OSCILLATOR
For a 50% duty cycle, the resistors RA and RB may be
connected as in Figure 14. The time period for the output
high is the same as previous, t1 = 0.693 RA C. For the output
low it is t2 =
Thus the frequency of oscillation is
LII
FIGURE 14. 50% Duty Cycle Oscillator
Note that this circuit will not oscillate if RB is greater than 1/2 RA because
the junction of RA and RB cannot bring pin 2 down to 1/3 VCC and trigger the lower
comparator.
ADDITIONAL INFORMATION
Adequate power supply bypassing is necessary to protect associated
circuitry. Minimum recommended is 0.1μF in parallel with 1μF electrolytic. Lower
comparator storage time can be as long as 10μs when pin 2 is driven fully to ground for
triggering. This limits the monostable pulse width to 10μs minimum. Delay time reset to
output is 0.47μs typical. Minimum reset pulse width must be 0.3μs, typical. Pin 7 current
switches within 30ns of the output (pin 3) voltage.
LIII
Physical Dimensions inches (millimeters) unless otherwise noted
Small Outline Package (M) NS Package Number M08A
LIV
LV
8-Lead (0.118” Wide) Molded Mini Small Outline Package
NS Package Number MUA08ALM555
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Molded Dual-In-Line Package (N)
NS Package Number N08E
LVI
VOLTAGE REGULATOR
INTRODUCTION
A voltage regulator is an electrical regulator designed to automatically
maintain a constant voltage level. It may use an electromechanical mechanism, or
passive or active electronic components. Depending on the design, it may be used to
regulate one or more ac or dc voltages. With the exception of shunt regulators, all
modern electronic voltage regulators operate by comparing the actual output voltage to
some internal fixed reference voltage. Any difference is amplified and used to control the
regulation element. This forms a negative feedback servo control loop. If the output
voltage is too low, the regulation element is commanded to produce a higher voltage. For
some regulators if the output voltage is too high, the regulation element is commanded to
produce a lower voltage; however, many just stop sourcing current and depend on the
current draw of whatever it is driving to pull the voltage back down. In this way, the
output voltage is held roughly constant. The control loop must be carefully designed to
produce the desired tradeoff between stability and speed of response.
Different types of voltage regulators
 Electromechanical regulator
 Mains regulators
 Coil rotation ac voltage regulator
 Ac voltage stabilizer
 Dc voltage stabilizer
 Active regulators
•
Linear regulators
•
Switching regulators
•
Scr regulators
•
Hybrid regulators
LVII
Electromechanical regulators
Circuit design for a simple electromechanical regulator.
Graph of voltage output on a time scale.
In older electromechanical regulators, voltage regulation is easily
accomplished by coiling the sensing wire to make an electromagnet. The magnetic field
produced by the voltage attracts a moving ferrous core held back under spring tension or
gravitational pull. As the voltage increases, the magnetic field strength also increases,
pulling the core towards the field and opening a mechanical power switch. As the voltage
decreases, the spring tension or weight of the core causes the core to retract, closing the
switch allowing the power to flow once more.
LVIII
If the mechanical regulator design is sensitive to small voltage
fluctuations, the motion of the solenoid core can be used to move a selector switch across
a range of resistances or transformer windings to gradually step the output voltage up or
down, or to rotate the position of a moving-coil AC regulator.
Early automobile generators and alternators had a mechanical
voltage regulator using one, two, or three relays and various resistors to stabilize the
generator's output at slightly more than 6 or 12 V, independent of the engine’s rpm or the
varying load on the vehicle's electrical system. Essentially, the relay(s) employed pulse
width modulation to regulate the output of the generator, controlling the field current
reaching the generator (or alternator) and in this way controlling the output voltage
produced.
The regulators used for generators (but not alternators) also disconnect
the generator when it was not producing electricity, thereby preventing the battery from
discharging back through the stopped generator. The rectifiers diodes in an alternator
automatically perform this function so that a specific relay is not required; this
appreciably simplified the regulator design.
More modern designs now use solid state technology (transistors) to perform
the same function that the relays perform in electromechanical regulators.
Mains regulators
Electromechanical regulators have also been used to regulate the voltage on AC
power distribution lines. These regulators generally operate by selecting the appropriate
tap on a transformer with multiple taps. If the output voltage is too low, the tap changer
switches connections to produce a higher voltage. If the output voltage is too high, the
tap changer switches connections to produce a lower voltage. The controls provide a
dead band wherein the controller will not act, preventing the controller from constantly
hunting (constantly adjusting the voltage) to reach the desired target voltage.
LIX
Coil-rotation AC voltage regulator
Basic design principle and circuit diagram for the rotating-coil AC voltage regulator .
This is an older type of regulator used in the 1920's that uses the principle
of a fixed-position field coil and a second field coil that can be rotated on an axis in
parallel with the fixed coil.
When the movable coil is positioned perpendicular to the fixed coil, the magnetic forces
acting on the movable coil balance each other out and voltage output is unchanged.
Rotating
the coil in one direction or the other away from the center position will
increase or decrease voltage in the secondary movable coil.
This type of regulator can be automated via a servo control mechanism to
advance the movable coil position in order to provide voltage increase or decrease. A
braking mechanism or high ratio gearing is used to hold the rotating coil in place against
the powerful electromagnetic forces acting on the moving coil.
The overall construction is extremely similar to the design of standard AC
dynamo windings, with the primary difference being that the rotor does not spin in this
device, and instead is held against spinning so the fields of the rotor and stator can act on
each other to increase or decrease the line voltage.
AC voltage stabilizers
A voltage stabilizer is a type of household mains regulator which uses a
continuously variable autotransformer to maintain an AC output that is as close to the
standard or normal mains voltage as possible, under conditions of fluctuation. It uses a
servomechanism (or negative feed back) to control the position of the tap (or wiper) of
the autotransformer, usually with a motor. An increase in the mains voltage causes the
LX
output to increase, which in turn causes the tap (or wiper) to move in the direction that
reduces the output towards the nominal voltage.
An alternative method is the use of a type of saturating transformer
called a ferroresonant transformer or constant-voltage transformer. These
transformers use a tank circuit composed of a high-voltage resonant winding and a
capacitor to produce a nearly constant average output with a varying input. The
ferroresonant approach is attractive due to its lack of active components, relying on the
square loop saturation characteristics of the tank circuit to absorb variations in average
input voltage. Older designs of ferroresonant transformers had an output with high
harmonic content, leading to a distorted output waveform. Modern devices are used to
construct a perfect sinewave. The ferroresonant action is a flux limiter rather than a
voltage regulator, but with a fixed supply frequency it can maintain an almost constant
average output voltage even as the input voltage varies widely.
The ferro resonant transformers, which are also know as Constant Voltage
Transformers (CVTs) or ferros are also a good surge suppressors, and it provides high
isolation and an inherent shortcircuit protections.
It can operate with an input voltage range as wide as ±40% or more of the
nominal voltage.Output power factor remains in the range of 0.96 or higher from half to
full load.Because it regenerates an output voltage waveform, output distortion, which is
typically less than 4%, is independent of any input voltage distortion, including
notching.Efficiency at full load is typically in the range of 89% to 93%. However, at low
loads, efficiency can drop below 60% and no load losses can be as high as 20%.
The current-limiting capability also becomes a handicap when a
CVT is used in an application with moderate to high inrush current like motors,
transformers or magnets. In this case, the CVT has to be sized to accommodate the peak
current, thus forcing it to run at low loads and poor efficiency.
Minimum maintenance is required beyond annual replacement of failed
capacitors. Redundant capacitors built into the units allow several capacitors to fail
between inspections without any noticeable effect to the device's performance.Output
voltage varies about 1.2% for every 1% change in supply frequency. For example, a 2PRAKASAM ENGINEERING COLLEGE
LXI
Hz change in generator frequency, which is very large, results in an output voltage
change of only 4%, which has little effect for most loads.It accepts 100% single-phase
switch-mode power supply loading without any requirement for derating, including all
neutral components.
Input current distortion remains less than 8% THD even when supplying
nonlinear loads with more than 100% current THD.One of the draw back of
CVT(constant voltage transformer) is its higher size and high audible humming sound.
DC voltage stabilizers
Many simple DC power supplies regulate the voltage using a shunt regulator
such as a zener diode, avalanche breakdown diode, or voltage regulator tube. Each of
these devices begins conducting at a specified voltage and will conduct as much current
as required to hold its terminal voltage to that specified voltage. The power supply is
designed to only supply a maximum amount of current that is within the safe operating
capability of the shunt regulating device (commonly, by using a series resistor). In shunt
regulators, the voltage reference is also the regulating device.If the stabilizer must
provide more power, the shunt regulator output is only used to provide the standard
voltage reference for the electronic device, known as the voltage stabilizer. The voltage
stabilizer is the electronic device, able to deliver much larger currents on demand.
Active regulators
Because they (essentially) dump the excess current not needed by the load, shunt
regulators are inefficient and only used for low-power loads. When more power must be
supplied, more sophisticated circuits are used. In general, these can be divided into
several classes:

Linear regulators


SCR regulators
LXII
Linear regulators
Linear regulators are based on devices that operate in their linear region
(in contrast, a switching regulator is based on a device forced to act as an on/off switch).
In the past, one or more vacuum tubes were commonly used as the variable resistance.
Modern designs use one or more transistors instead. Linear designs have the advantage
of very "clean" output with little noise introduced into their DC output, but are less
efficient and unable to step-up or invert the input voltage like switched supplies.
Entire linear regulators are available as integrated circuits. These chips come in either
fixed or adjustable voltage types.
Switching regulators rapidly switch a series device on and off. The duty
cycle of the switch sets how much charge is transferred to the load. This is controlled by
a similar feedback mechanism as in a linear regulator. Because the series element is
either fully conducting, or switched off, it dissipates almost no power; this is what gives
the switching design its efficiency. Switching regulators are also able to generate output
voltages which are higher than the input, or of opposite polarity — something not
possible with a linear design.
Like linear regulators, nearly-complete switching regulators are also
available as integrated circuits. Unlike linear regulators, these usually require one
external component: an inductor that acts as the energy storage element. (Large-valued
inductors tend to be physically large relative to almost all other kinds of componentry, so
they are rarely fabricated within integrated circuits and IC regulators — with some
exceptions.)
SCR regulators
Regulators powered from AC power circuits can use silicon controlled
rectifiers (SCRs) as the series device. Whenever the output voltage is below the desired
value, the SCR is triggered, allowing electricity to flow into the load until the AC mains
voltage passes through zero (ending the half cycle). SCR regulators have the advantages
LXIII
of being both very efficient and very simple, but because they cannot terminate an ongoing half cycle of conduction, they are not capable of very accurate voltage regulation
in response to rapidly-changing loads.
Combination (hybrid) regulators
Many power supplies use more than one regulation method in series. For
example, the output from a switching regulator can be further regulated by a linear
regulator. The switching regulator accepts a wide range of input voltages and efficiently
generates a (somewhat noisy) voltage slightly above the ultimately desired output. That
is followed by a linear regulator that generates exactly the desired voltage and eliminates
nearly all the noise generated by the switching regulator. Other designs may use an SCR
regulator as the "pre-regulator", followed by another type of regulator. An efficient way
of creating a variable-voltage, accurate output power supply is to combine a multi-tapped
transformer with an adjustable linear post-regulator.
LM78L05 voltage regulator IC
Description
The MC78XX/LM78XX/MC78XXA series of three terminal positive
regulators are available in the TO-220/D-PAK package and with several fixed output
voltages, making them useful in a wide range of applications. Each type employs internal
current limiting, thermal shut down and safe operating area protection, making it
essentially indestructible. If adequate heat sinking is provided, they can deliver over 1A
output current. Although designed primarily as fixed voltage regulators, these devices
can be used with external components to obtain adjustable voltages and currents.
LXIV
Internal Block Digram:
Features:
o Output Current up to 1A
o Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V
o Thermal Overload Protection
o Short Circuit Protection
o Output Transistor Safe Operating Area Protection
LXV
Typical Perfomance Characteristics
Figure 1. Quiescent Current
Figure 2. Peak Output Current
Figure 3. Output Voltage
LXVI
Figure 4. Quiescent Current
Typical Applications
Figure 5. DC Parameters
LXVII
Figure 6. Load Regulation
Figure 7. Ripple Rejection
Figure 8. Fixed Output Regulator
LXVIII
Figure 9. Constant Current Regulator
Figure 10. Circuit for Increasing Output Voltage
LXIX
Figure 11. Adjustable Output Regulator (7 to 30V)
Figure 12. High Current Voltage Regulator
LXX
Figure 13. High Output Current with Short Circuit Protection
Figure 14. Tracking Voltage Regulator
Figure 15. Split Power Supply ( ±15V-1A)
LXXI
Figure 16. Negative Output Voltage Circuit
Figure 17. Switching Regulator
Mechanical Dimensions
LXXII
LXXIII
LED
LED's are special diodes that emit light when connected in a circuit. They are
frequently used as "pilot" lights in electronic appliances to indicate whether the circuit is
closed or not. A a clear (or often colored) epoxy case enclosed the heart of an LED, the
semi-conductor chip.
LEDs must be connected the correct way round, the diagram may be labelled a or + for
anode and k or - for cathode (yes, it really is k, not c, for cathode!). The cathode is the
short lead and there may be a slight flat on the body of round LEDs. If you can see inside
the LED the cathode is the larger electrode
LEDs can be damaged by heat when soldering, but the risk is
small unless you are very slow. No special precautions are needed for soldering most
LEDsThe most important part of a light emitting diode (LED) is the
semi-conductor chip located in the center of the bulb as shown at the
right. The chip has two regions separated by a junction. The p region is
dominated by positive electric charges, and the n region is dominated
by negative electric charges. The junction acts as a barrier to the flow
of electrons between the p and the n regions. Only when sufficient voltage is applied to
the semi-conductor chip, can the current flow and the electrons cross the junction into the
p region. charges. The junction acts as a barrier to the flow of electrons between the p
and the n regions. Only when sufficient voltage is applied to the
semi-conductor chip, can the current flow, and the electrons cross
the junction into the p region. In the absence of a large enough
LXXIV
electric potential difference (voltage) across the LED leads, the junction presents an
electric potential barrier to the flow of electrons.
What Causes the LED to Emit Light and What Determines the Color of
the Light?
When sufficient voltage is applied to the chip across the leads of the
LED, electrons can move easily in only one direction across the junction between the p
and n regions. In the p region there are many more positive than negative charges. In the
n region the electrons are more numerous than the positive electric charges. When a
voltage is applied and the current starts to flow, electrons in the n region have sufficient
energy to move across the junction into the p region. Once in the p region the electrons
are immediately attracted to the positive charges due to the mutual Coulomb forces of
attraction between opposite electric charges. When an electron moves sufficiently close
to a positive charge in the p region, the two charges "re-combine". Each time an electron
recombines with a positive charge, electric potential energy is converted into
electromagnetic energy. For each recombination of a negative and a positive charge, a
quantum of electromagnetic energy is emitted in the form of a photon of light with a
frequency characteristic of the semi-conductor material (usually a combination of the
chemical elements gallium, arsenic and phosphorus). Only photons in a very narrow
frequency range can be emitted by any material. LED's that emit different colors are
made of different semi-conductor materials, and require different energies to light them.
How Much Energy Does an LED Emit?
The electric energy is proportional to the voltage needed to cause
electrons to flow across the p-n junction. The different colored LED's emit
predominantly light of a single color. The energy (E) of the light emitted by an LED is
related to the electric charge (q) of an electron and the voltage (V) required to light the
LED by the expression: E = qV Joules. This expression simply says that the voltage is
proportional to the electric energy, and is a general statement which applies to any
circuit, as well as to LED's. The constant q is the electric charge of a single electron, -1.6
x 10-19 Coulomb.
Testing an LED
LXXV
Never connect an LED directly to a battery or power supply!
It will be destroyed almost instantly because too much current will
pass through and burn it out.
LEDs must have a resistor in series to limit the current to a safe
value, for quick testing purposes a 1k
resistor is suitable for most
LEDs if your supply voltage is 12V or less. Remember to connect the LED the correct
way round!
Colours of LEDs
LEDs are available in red, orange,
amber, yellow, green, blue and white.
Blue and white LEDs are much more
expensive than the other colours.
The colour of an LED is determined by
the semiconductor material, not by the colouring of the 'package' (the plastic body).
LEDs of all colours are available in uncoloured packages which may be diffused (milky)
or clear (often described as 'water clear'). The coloured packages are also available as
diffused
(the
standard
type)
or
transparent.
Tri-colour LEDs
The most popular type of tri-colour LED has a red and a green
LED combined in one package with three leads. They are called tri-colour
because mixed red and green light appears to be yellow and this is
produced when both the red and green LEDs are on.
The diagram shows the construction of a tri-colour LED. Note the
different lengths of the three leads. The centre lead (k) is the common
cathode for both LEDs, the outer leads (a1 and a2) are the anodes to the
LEDs allowing each one to be lit separately, or both together to give the third colour.
LXXVI
Bi-colour LEDs
A bi-colour LED has two LEDs wired in 'inverse parallel' (one forwards, one
backwards) combined in one package with two leads. Only one of the LEDs can be lit at
one time and they are less useful than the tri-colour LEDs described above.
Sizes, Shapes and Viewing angles of LEDs
LEDs are available in a wide variety of sizes
and shapes. The 'standard' LED has a round crosssection of 5mm diameter and this is probably the best LED Clip
type for general use, but 3mm round LEDs are also
Photograph © Rapid Electronics
popular.
Round cross-section LEDs are frequently used and they are very easy to install on boxes
by drilling a hole of the LED diameter, adding a spot of glue will help to hold the LED if
necessary. LED clips are also available to secure LEDs in holes. Other cross-section
shapes include square, rectangular and triangular.
As well as a variety of colours, sizes and shapes, LEDs also vary in their viewing angle.
This tells you how much the beam of light spreads out. Standard LEDs have a viewing
angle of 60° but others have a narrow beam of 30° or less.
Calculating an LED resistor value
An LED must have a resistor connected in
series to limit the current through the LED, otherwise it
will burn out almost instantly.
The resistor value, R is given by:
R = (VS - VL) / I
VS = supply voltage VL = LED voltage (usually 2V, but 4V for blue and white LEDs)
I = LED current (e.g. 20mA), this must be less than the maximum permitted
LXXVII
If the calculated value is not available choose the nearest standard resistor value which is
greater, so that the current will be a little less than you chose. In fact you may wish to
choose a greater resistor value to reduce the current (to increase battery life for example)
but this will make the LED less bright.
For example
If the supply voltage VS = 9V, and you have a red LED (V L = 2V), requiring a current I =
20mA = 0.020A, R = (9V - 2V) / 0.02A = 350 , so choose 390
(the nearest standard
value which is greater).
Working out the LED resistor formula using Ohm's law
Ohm's law says that the resistance of the resistor, R = V/I, where:
V = voltage across the resistor (= VS - VL in this case) I = the current through the resistor
So R=(VS-VL)/I
Connecting LEDs in series
If you wish to have several LEDs on at the same time it may be possible to
connect them in series. This prolongs battery life by lighting several LEDs with the same
current as just one LED.
All the LEDs connected in series pass the same
current so it is best if they are all the same type. The power
supply must have sufficient voltage to provide about 2V for
each LED (4V for blue and white) plus at least another 2V
for the resistor. To work out a value for the resistor you
must add up all the LED voltages and use this for VL.
Example
calculations:
A red, a yellow and a green LED in series need a supply voltage of at least
3 × 2V + 2V = 8V, so a 9V battery would be ideal. VL = 2V + 2V + 2V = 6V (the three
LED voltages added up). If the supply voltage V S is 9V and the current I must be 15mA
LXXVIII
= 0.015A, Resistor R = (VS - VL) / I = (9 - 6) / 0.015 = 3 / 0.015 = 200 ,
so choose R = 220
(the nearest standard value which is greater).
Avoid connecting LEDs in parallel!Connecting several LEDs in
parallel with just one resistor
shared between them is generally not a good idea.
If the LEDs require slightly different voltages only the lowest voltage LED will light and
it may be destroyed by the larger current flowing through it. Although identical LEDs
can be successfully connected in parallel with one resistor this rarely offers any useful
benefit because resistors are very cheap and the current used is the same as connecting
the LEDs individually. If LEDs are in parallel each one should have it sown resistor. In
multi-axis applications that do not require simultaneous motion, where only one motor
moves at a time, it is possible to "multiplex" the step and direction pulse from one
indexer to multiple drivers.
LXXIX
OPERATION OF STEPPER MOTOR USING UCN5804B
TRANSLATOR
To run the stepper controller using the on-board oscillator, install jumper J1 in
the “A” position and leave J2 open.On the four-position DIP switch,set S1, S2, S3, and
S4 all to the “OFF” position. Switch the DC power source ON and the stepper motor
should start to turn. The speed can be regulated with potentiometer R13. Installing jumper
J2 will switch to a low-speed range. If you try to drive a stepper motor too fast or with too
large of a load, it can stall .With the motor turning properly, you can switch S2, S3, and
S4 to change the direction, step size, or phasing (see Figure a). Note that S1 is
FIG.a
the output enable and will stop the motor when the switch is in the “ON”
position. To control the stepper functions remotely, set all of the DIP switches to the
“OFF” position and then use P3 to connect the control signals to an external
microcontroller or toggle switches.To operate the stepper controller in the single-step
mode, install jumper J1 in the “B” position. Each time you press witch S5, the LN555
(U3) will produce a single pulse and will cause the UCN5804 to advance the motor one
sequence position. The motor sequence will still be determined by the settings of S2, S3,
and S4.For single-step to work properly,you must release S5 before U3 completes its
output pulse or else the LM555 will automatically re-trigger. The single-step mode is a
great educational tool because you can actually observe the various step sequences in the
LEDs (L1-4).
U1 can generate waveforms for three different sequence modes:
LXXX
(1)FULL-STEP with two phases energized,
(2) FULL-STEP WAVE and
(3) HALF-STEP.
The waveforms for these three sequence modes are shown in Figure b.
FIG.b
LXXXI
APPLICATIONS:
A Unique feature of the stepper motor is that it’s output shaft rotates in a series discrete
angular intervals or steps. due to feature in recent years there has been wide spread
demand of stepper motor.
And this will be used different applications like
 Robotics
 Type writers and line printers
 Computer peripherals
 Textile industry
 Tape drives,floppy disk drives
 Numerically controlled machine tools
 Process control systems,X-Y plotters
 Commercial applications,military and medical applications
 Mixing,cutting,striking,metering.
 Manufacture packed foodstuffs
 Production science fiction movies.
Conclusion:
here Our project provides not only for controlling the motor with
technique is useful for different types controls such as controlling the
satellites,controlling the robots e.t.c
LXXXII
HARDWARE COMPONENTS
Stepper motor
LXXXIII
Complete kit
LXXXIV

speed control of stepper motor by using ucn5804b translator

Transcription

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