Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Homework Tasks

The 555 Fan

1 Pulse Width Modulation (PWM)

Learn It

  • The 555 timer chip creates pulses on the outputs based on how quickly the capacitor on the input charges and discharges.
  • We want to control the speed of the fan, so how can we use these pulses to change how fast the motor spins.
  • Below you will be introduced to the PWM concept, you only need to watch the first 2 minutes.

  • Below is a video of the 555 Fan connected to an oscilloscope where you can visually see the pulse widening and narrowing.

Research It

  • Conduct a little web research to find out what is meant by Pulse Width Modulation (PWM).

Badge It - Silver

  • Upload your research, explaining how PWM works. You need to include images.

Badge It - Gold

  • A 555 timer circuit can generate PWM, but a microcontroller (Genie chip) can do the same thing.
  • We can program an output of a Genie chip to create PWM.
  • Design the circuit below.


  • The flowchart is below.


  • Describe what happens when you adjust the potentiometer.

Badge It - Platinum

  • Write a program that allows the user to change the speed the fan spins at by using what you have learned about PWM.