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Pulse Generation using Timer in Siemens PLC

This article is about a pulse generation PLC program using Siemens TIA PORTAL.

In industries, we use special audio and visual indications to notify the operators about the alarms and trips of the process. Different types of indications are flashing LED, beacons with different tones, etc.

We can set the rate of pulses from slow to fast as per our requirement by changing the timing of the timers. Here we will be discussing the pulse generation using timer instruction in Siemens PLC.

Below I have explained the PLC program for pulse generation.

Inputs and Outputs

  • Inputs: START(I0.0), STOP (I0.1)
  • Outputs: LED_INDICATION (Q0.0)
  • Timers: T0 & T1
  • Memory Bit: M0.0

Pulse Generation using TimerPulse Generation using Timer in Siemens PLC


When you press the start button (%I0.0), then the flip-flop (M0.0) energizes then it will pass the signal through NC contact of timer (T2) then timer 1 will energize.

Here I have used S_Pulse timer which will run in our case for 2 seconds after 2 seconds timer will energize.

We can change the timing of the timer to change the flashing rate as per our requirement.

If Timer 1 is not energized then first NOT instruction will energize the Timer 2 allowing output to turn ON for 2 seconds.

Both the timers will run for 2 seconds simultaneously allowing LED to turn ON and OFF for every 2 seconds thus flashing the LED.

Author: Suhel Patel

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Kumar April 5, 2020 at 11:48 am


What is the need of two timers?

Suhel April 5, 2020 at 1:03 pm

To generate the pulses, 1 timer stay ON for 2 sec, so another timer will remain OFF for 2 sec. thus generating pulse for that interval


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Pulse Generation using Timer in Siemens PLC

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