Control of Tea Dispenser PLC program


In this session we are gonna discuss a PLC program of a tea dispenser


I/O assignments


Cup detection X000 (ON when cup is present)
Dispense tea button X001
Check tea leaves button X002
Replenish water tank lower limit switch X003
Replenish water tank upper limit switch X004


Change tea leaves indicator lamp Y000
Dispense tea output Y001
Replenish water output Y003

Explanation of operation

(1) When cup detection X000 is ON, and dispense tea button X001 is pressed (X001 turns ON), dispense tea output Y001 operates, and hot water is poured into the cup. Hot water is poured only for the duration that the button is pressed, and stops being poured when you release your hand from the button.
When cup detection X000 is OFF, hot water is not poured even by pressing dispense tea button X001.

(2) When water in the replenish water tank gets low, lower limit switch X003 turns ON and replenish water output Y003 operates.
When replenish water output Y003 operates and water is poured into the tank, upper limit switch X004 finally turns ON, and replenish water output Y003 becomes non-operational.

(3) When water is replenished five times, the change tea leaves indicator lamp lights.

(4)When the check button is pressed, the change tea leaves indicator lamp goes out.

Ladder Diagram


(1)Output Y001 operates when both inputs X000 or X001 turns ON.

(2)When input X003 turns ON, output Y003 operates, and when input X004 turns ON, output Y003 becomes non-operational.

(3)Each time that output Y003 operates, the value of counter C0 is incremented by one. When C0 reaches “5”, Y000 operates.

(4)When input X002 turns ON, the value of counter C0 returns to “0” and output Y000 becomes non-operational.

You can practice this plc program at a free simulator link in the below
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