PWM generation using 555 timer using Proteus

PWM stands for pulse width modulation. The duty cycle of the PWM signal varies but the frequency remains the same. PWM signals are widely used to control intensity of the LEDs and also to control the speed of the motors. They can be used for many more applications. 555 is the basic component which can be used to generate PWM device in its Astable mode of operation. Is is easy to implement as it requires very few components. We are going to generate Pwm using 555 timer IC. Learn about working of Astable Multivibrator.

Learn about Pwm using Arduino.

Circuit Diagram:

Circuit Diagram of Variable Duty Cycle PWM Generation
PWM-circuit Diagram-IC555


Select the below components from the library into proteus:


The Required components are:

  • IC-555
  • Diode- 1N4007
  • POT-HG
  • RES (Resistors)
  • CAP(Capacitors)
  • 9V Power supply

Don’t get confused select the resistors and capacitors value similar to the circuit diagram shown above.

Working of Variable duty cycle PWM using 555:

  • Initially the trigger voltage [2nd Pin] is below 1/3 VCC. Therefore the output voltage will be high.
  • The output voltage will charge the capacitor through the diode and Pot. Hence when the voltage across the capacitor reaches above 2/3VCC the comparator gets reset and the output switches to 0v. Now the capacitor starts discharging.
  • Once the capacitor voltage crosses 1/3VCC due to discharging the comparator inside IC555 again switches and the output voltage becomes high.
  • The above process gets repeated.

The charging of capacitor is the function of RV1*RD*C. Where RV1 is the pot resistance. Hence varying the pot we can vary the duty cycle of the PWM output.


PWM Output:

PWM- Output
PWM- Output

Video- How to Change Duty Cycle.



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