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Single Push button to ON and OFF a Bulb using Ladder Logic

Learn how to use Single Push button to ON and OFF a Bulb using Ladder Logic in programmable logic controllers (PLC) control system.

  • I0.0  : Input Push-Button (Normally-Open)
  • Q0.0 : Output Coil (Bulb)
  • Q1.5 & Q1.6 : Flags

Single Push button Ladder Logic

As soon as the push button I0.0 (N-O) is pressed ,it becomes N-C and coil Q1.5 (flag) is energized. The another flag Q1.6 will not energize as the output coil contact  Q0.0 is N-O, which breaks the circuit to the flag Q1.6.

As soon as the flag Q1.5 is energized ,the contact Q1.5 (N-O) becomes N-C and out bulb coil Q0.0 gets energized and bulb becomes ON.

Single Push button to ON and OFF a Bulb using Ladder Logic

Now, if the push button is released the coil Q0.0 will remain energized because of latching applied as latch contact Q0.0 (N-O) in last rung. To switch off the bulb the push button is again pressed which closes the N-O contact of o/p coil Q0.0 and energizes the flag coil Q1.6.

Due to energize of flag Q1.6 , the N-C contact of this flag in last rung becomes N-O  and as a result of this ,the last rung goes false and output coil Q0.0   is de-energized and bulb goes OFF.

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Jakaria December 18, 2019 at 9:03 pm

Very nc

Sergey January 15, 2020 at 6:01 pm

DO not fill people, this will not work.

Raj January 16, 2020 at 10:38 pm

This will not work….gave a try

Brett March 21, 2020 at 9:41 am

I’m no expert but this should turn it on, just to turn it right off again. Just based on me reading it. The bulb will open the top closed contacts to open, and the contacts below that to close, causing the second flag to get power. Once that gets power, it will then open it’s corresponding contacts, cutting off power to the bulb.

So it will turn it on, then turn off. Basically flicker. Though maybe I’m wrong in my observation, though I don’t see how it could work regardless.

Olgierd December 4, 2020 at 10:41 am

This will cause output Q0.0 to flicker as it will be set in one program cycle just to get reset in next and again and again.
You will need to add rising edge detection dor input I0.0 for it to work.

Ilahi December 12, 2020 at 12:47 pm

It’s a flicker for led not working properly as gets flick when turn on and similar when turning off.


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Single Push button to ON and OFF a Bulb using Ladder Logic

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