1.
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a. Identify real inputs and outputs:
○ Real Inputs:
■ Start Pushbutton (PB1)
■ Stop Pushbutton (PB2)
■ Temperature Switch (TS3)
■ Foot Switches (FS4 and FS5)
○ Real Outputs:
■ Solenoids (SOL1 and SOL2)
■ Heating Element (H3)
■ Lamps (PL1, PL2, PL3)
b. Assign the I/O addresses:
○ PLC has modularity of 8 points per module.
○ Inputs:
■ Start PB1 = I0.0
■ Stop PB2 = I0.1
■ Temperature Switch (TS3) = I0.2
■ Foot Switch 1 (FS4) = I0.3
■ Foot Switch 2 (FS5) = I0.4
○ Outputs:
■ Solenoid 1 (SOL1) = O0.0
■ Solenoid 2 (SOL2) = O0.1
■ Heating (H3) = O0.2
■ Lamp 1 (PL1) = O0.3
■ Lamp 2 (PL2) = O0.4
■ Lamp 3 (PL3) = O0.5
c. Assign internal addresses:
○ CR1 = M0.0
○ CR2 = M0.1
○ CR3 = M0.2
d. Draw I/O connection diagram:
○ Inputs: Connect inputs like PB1, PB2, TS3, FS4, FS5 to the corresponding
I/O terminals.
○ Outputs: Connect solenoids, heating element, and lamps to their respective
output terminals.
2.
Create a ladder diagram for the competition push-button:
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Group A: Two elementary students with two push buttons.
Group B: One junior high student with one push button.
Group C: One teacher with one push button.
The fastest person to press their button turns on their light, and other lights are
locked out.
Approach:
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Use latch coils for each light output.
Each push button triggers a corresponding output and disables the other buttons by
energizing a latching relay.
The MC (Master Control) has the ability to reset all latches.
Ladder Logic:
1.
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4.
Group A PB1 turns on light A and locks out other inputs.
Group B PB2 turns on light B and locks out other inputs.
Group C PB3 turns on light C and locks out other inputs.
MC reset button clears all latches.
3.
Draw a PLC ladder diagram for the mixing vat system:
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a. Inlet valve opens until the vat is full:
○ Start button activates the inlet valve (controlled by a solenoid).
○ The level switch (normally open) closes when the vat is full, deactivating the
inlet valve.
b. Mixer motor comes on for 5 minutes:
○ After the vat is full, start a 5-minute timer.
○ The mixer motor is activated while the timer runs.
c. Outlet valve opens until the vat is empty:
○ Once mixing is complete, open the outlet valve until the level switch detects
an empty vat.
Ladder Logic:
1. Start button triggers the inlet solenoid and timer.
2. Timer triggers mixer motor for 5 minutes.
3. When mixing is done, the outlet solenoid opens and remains open until the vat is
empty.
4.
Draw a PLC ladder diagram for the motor control system:
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Normally Open start button (NO)
Normally Closed stop button (NC)
Overload protection device (normally closed, opens if motor overheats)