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PLC Basic Course on Ladder Logic Diagrams Programming
Exercise 1: Combination Circuits using Contacts/Switches and Relays/Coils
1.1. The door bell y0 is only rung when the door switch push button x0 is pressed
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PLC Basic Course on Ladder Logic Diagrams Programming
1.2. Define OR Gate function with the help of ladder.
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PLC Basic Course on Ladder Logic Diagrams Programming
1.3. Define NOR Gate function with the help of ladder
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PLC Basic Course on Ladder Logic Diagrams Programming
1.4. Define AND Gate function with the help of ladder
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PLC Basic Course on Ladder Logic Diagrams Programming
1.5. Define NAND Gate function with the help of ladder
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PLC Basic Course on Ladder Logic Diagrams Programming
1.6. Define XOR Gate function with the help of ladder
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PLC Basic Course on Ladder Logic Diagrams Programming
1.7. Multiplexer Circuit. Use the truth table below
x0 x1 y0 y1 y2 y3
0 0 0 0 0 1
0 1 0 0 1 0
1 0 0 1 0 0
1 1 1 0 0 0
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PLC Basic Course on Ladder Logic Diagrams Programming
Problems:
Problem 1-A. Design circuit to control start/Stop operation of a Fan. (Use two push buttons X0, X1
for start stop operations)
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PLC Basic Course on Ladder Logic Diagrams Programming
Problem 1-B. Solve (Problem 1-A).Design a circuit to control start/Stop operation of a Fan. (Use two
push buttons X0, X1 for start stop operations) using Hold condition of Push Button
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PLC Basic Course on Ladder Logic Diagrams Programming
Problem 1-C. Solve (Problem 1-A).Design a circuit to control start/Stop operation of a Fan. (Use two
push buttons X0, X1 for start stop operations) using Hold condition of Push Button by Internal retentive
coil of PLC
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PLC Basic Course on Ladder Logic Diagrams Programming
Problem 1-D. Solve (Problem 1-A).Design a circuit to control start/Stop operation of a Fan. (Use two
push buttons X0, X1 for start stop operations) using Hold condition of Push Button by Set And Reset
Instruction of PLC.
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PLC Basic Course on Ladder Logic Diagrams Programming
Problem 1-E. Solve (Problem 1-A).Design a circuit to control start/Stop operation of a Fan. (Use two
push buttons X0, X1 for start stop operations) using only one pushes Button.
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PLC Basic Course on Ladder Logic Diagrams Programming
Problem 1-F. Solve (Problem 1-A).Design a circuit to control start/Stop operation of a Fan. (Use two
push buttons X0, X1 for start stop operations) using only one push Button by toggle instruction.
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PLC Basic Course on Ladder Logic Diagrams Programming
Exercise 2:
Timers
2.1. Timers CV accumulate counting after PV is met, when no stop contact is added.
2.2. Timer reset to its original value and starts counting again when stop contact of the
same timer is added.
2.3. Timer CV stops counting using built in function M1957.
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PLC Basic Course on Ladder Logic Diagrams Programming
PROBLEMS
Problem 2-A. Output y0 is "ON" After 20 Seconds when Push Button X0 is pushed.
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PLC Basic Course on Ladder Logic Diagrams Programming
Problem 2-B Output y0 is flickered by using two timers, when push Button X0 is pushed. (Use
5 second interval between ON/OFF)
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PLC Basic Course on Ladder Logic Diagrams Programming
Problem 2-C X0 and X1 are two push buttons. When X1 is pushed Lamp "L1" and "L2" will go
"ON" after 10 seconds "L1" will be "OFF" and "L3" "ON". Whereas "L2" remains
"ON". Whole Circuit is stopped by Pushing "X0".
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PLC Basic Course on Ladder Logic Diagrams Programming
Problem 2-D Motor control circuits
There are three push buttons X0, X1, X2. When X1 is pushed motor Starts rotating Clock wise. When
push Button X2 is pushed it rotates CCW while it stops Rotating by pushing X0.
(a) Design the ladder logic assuming there is no delay in changing the direction of motor
(b) Design the ladder logic Assuming 10 second delay in changing the direction of motor
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PLC Basic Course on Ladder Logic Diagrams Programming
Problem 2-E Traffic Signals Ladder logic. Push Button X0 is used to start the signals. Green signal is
"ON" for 30 seconds then yellow for 10 seconds then red for 30 seconds then
yellow for 10 seconds and it repeats.
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PLC Basic Course on Ladder Logic Diagrams Programming
COUNTERS
Exercise 3:
Problem 3-A. When push button X1 is pressed 10 times then Led1 is "ON". It is "OFF" by X0.
Note: Problem with push button: It creates noise due to mechanical contacts. Solution: function
of plc difu and upper/down edge contact input
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PLC Basic Course on Ladder Logic Diagrams Programming
Problem 3-B. Solve problem 3-A above using upper/down edge contact or Difu
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PLC Basic Course on Ladder Logic Diagrams Programming
Problem 3-C. Counting Boxes: Boxes move continue on conveyor belt one by one. And one counter
counts boxes, when counter count 10 boxes then conveyor belt will be stopped
and alarm “ON”. After 1 minute alarm will be stopped and conveyor belt will be shut
down.
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PLC Basic Course on Ladder Logic Diagrams Programming
Problem 3-D. Automatic count boxes (use M1922). When counter counts 10 boxes then conveyor stop
and alarm "ON" and after "1" minute Alarm "FF"
NOTE: M1922 gives a pulse clock of 1 second
Other Instructions:
MOV
INC
Shift right
Shift left
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PLC Basic Course on Ladder Logic Diagrams Programming
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PLC Basic Course on Ladder Logic Diagrams Programming
This control system will work fine, so long as no one pushes both buttons at the same time. If someone were to do that, phases A and B would be short-circuited together by virtue of the fact that contactor M1 sends phases A and B straight to the motor and contactor M2 reverses them; phase A would be shorted to phase B and vice-versa. Obviously, this is a bad control system design! To prevent this occurrence from happening, we can design the circuit so that the energization of one contactor prevents the energization of the other. This is called
Interlocking and it is accomplished through the use of auxiliary contacts on each contactor, as such:
Now to add hold condition of push buttons and momentarily stop button
Now to add Delay Between the Change of Direction of Motor to accommodate the inertia forces.
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PLC Basic Course on Ladder Logic Diagrams Programming
Problem 3-C:
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