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Mid-Term Exam
Name:
ID
:
Notes
1. This is a closed book & closed notes exam
2. There are ( 4 ) problems
3. Do ALL the problems
4. The time allowed is ( 60 ) minuets
5. The exam weights 20% of the nal grade
Results:
Problem Marks
I
II
III
IV
Total
/6
/ 15
/ 10
/9
/ 40
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Scratch space...
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I. Using the ladder program shown in the gure, answer the questions that follows
1. What type of counter has been programmed?
2. What input address will cause the counter to increment?
3. What input address will cause the counter to decrement?
4. What input address will reset the counter to a count of zero?
5. When would output O:6/2 be energized?
6. Suppose the counter is rst reset, and then input I:2/6 is actuated 15 times and input I:3/8 is actuated 5
times. What is the accumulated count value?
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II. The next gure represents the process of making tea every day in the morning
Process:
When pressing the `start' button (push-button), the valve 1 (V1) opens,so the water pass through the valve to
the heating tank.
When the water level reaches the oat switch (FS), the valve should close and heating must begin (E is heater)
When the temperature reach the required level measured by the thermostat (TH) the heater should be disconnected and valve 2 (V2) should be opened for 10 seconds then the alarm bell is activated (as a sign that the tea jug
is lled now with hot water)
1. List the input and output devices in this process
2. Make a PLC ladder logic program to implement the above procedure. (make sure all devices names are shown
in the rungs)
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III.
1. Using timing diagram and your own language, explain the dierence between retentive timer and counter
instructions in PLC ladder language.
2. List 4 discrete input devices, 4 analogue input devices, 2 discrete output devices and 2 analogue output
devices that can be connected to a PLC
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IV. For the peace of PLC ladder logic program shown in the gure, the input signal used for switch I1/0 is shown
in the gure in black as indicated. After this portion of input signal has passed answer the following questions:
1. What is the state of O2:/0? (ON or OFF)
2. What is the value of C5:1 Acc.?
3. What is the value of T4:1 Acc.?
4. Draw the timing diagram as provided.
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