How to Program a Star-Delta System using 1 Button in PLC?

This PLC Program uses the differentiate UP (DIFU) and differentiate DOWN (DIFD) functions that can be used to teach PLC programming logic to students.

Star-Delta System using 1 Button

The PLC program only uses 1 button. TRIGGER_BUTTON (0.00) button is used to Turn On the system and Turn Off the system.

When the TRIGGER_BUTTON (0.00) button is Pressed once, the system is ON and when the TRIGGER_BUTTON (0.00) button is pressed once again, the system will be OFF.

Logic-1

When the TRIGGER_BUTTON (0.00) button is Pressed, the memory bit SYSTEM_ON (W0.00) will become a HIGH state. Because in this logic, the TRIGGER_BUTTON(0.00) button uses a NO contact Differentiate UP/DIFU type, the memory bit SYSTEM_ON (W0.00) changes to HIGH state when button TRIGGER_BUTTON (0.00) changes from LOW state to HIGH state.

When the memory bit SYSTEM_ON (W0.00) changes to a HIGH state, the output STAR_MODE (100.00) will be ON and the system will RUN in STAR mode.

After 5 seconds the system will change to DELTA mode, Output DELTA_MODE (100.01) becomes ON, and Output STAR_MODE (100.00) changes to OFF.

Logic-2

When the TRIGGER_BUTTON (0.00) button is Released, the memory bit IR_1 (W0.01) will become a HIGH state. Because in this logic, the TRIGGER_BUTTON (0.00) button uses a NO contact Differentiate DOWN/DIFD type, the memory bit IR_1 (W0.01) changes to the HIGH state when button TRIGGER_BUTTON (0.00) changes from the HIGH state to LOW state.

Logic-3

Memory bit IR_2 (W0.02) is used as an Interlock to Turn Off memory bit SYSTEM_ON (W0.00). So when the TRIGGER_BUTTON (0.00) button is Pressed again, the system will be OFF.

PLC I/O Details

Comment	Input (I)	Output(Q)	TIMER	Word Memory
TRIGGER_BUTTON	0.00
STAR_MODE		100.00
DELTA_MODE		100.01
SYSTEM_ON				W0.00
IR_1				W0.01
IR­_2				W0.02
TIMER_CUTOFF			T0000

PLC Programming

RUNG 0 (TRIGGER AREA)

In this Rung, when the TRIGGER_BUTTON (0.00) button is pressed, the memory bit SYSTEM_ON (W0.00) will become a HIGH state Because it uses Latching, the memory bit SYSTEM_ON (W0.00) remains in the HIGH state even though the TRIGGER_BUTTON (0.00) button is only Active for a moment.

The memory bit SYSTEM_ON (W0.00) will be in the LOW state when the NC contact of memory bit IR_2 (W0.02) is in the HIGH state.

RUNG 1

In this Rung, when the NO contact of memory bit SYSTEM_ON (W0.00) in the HIGH state and the TRIGGER_BUTTON (0.00) button is Released, the memory bit IR_1 (W0.01) will become to HIGH state. Because it uses Latching, the memory bit IR_1 (W0.01) remains in the HIGH state even though the TRIGGER_BUTTON (0.00) button is only Active for a moment.

RUNG 2

The memory bit IR_2 (W0.02) will be in the HIGH state when the NO contact of memory bit IR_1 (W0.01) in the HIGH state and the TRIGGER_BUTTON (0.00) button is Pressed.

RUNG 3 (STAR ​​MODE)

When the NO contact of memory bit SYSTEM_ON(W0.00) in the HIGH state, the STAR_MODE (100.00) output will be ON, and the TIMER_CUTOFF (T0000) timer Starts counting up to 5 seconds.

When the timer TIMER_CUTOFF (T0000) finishes counting, the STAR_MODE (100.00) output becomes OFF.

RUNG 4 (DELTA MODE)

The DELTA_MODE (100.01) output will be ON when the NO contact of memory bit SYSTEM_ON (W0.00) and the timer TIMER_CUTOFF (T0000) in HIGH state.

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