I have a system that modulates PWM current output, and for a demo targeted at a general audience, I want to show that the duty cycle of the output is being modulated.

The easy way to do this would be with an oscilloscope (seeing the output square wave), but again, not very flashy and simple for a general audience.

Two more ideas are lightbulbs and fans since their brightness and speed would vary with the duty cycle, but the problem there is that 80% brightness/fan speed is hard to distinguish from 60% for example.

So, I'm looking for a visual, aesthetically pleasing, current sensor that is easy to see and not too complicated in terms of circuitry.

  • \$\begingroup\$ Just increase the period, a PWM period of 10 seconds with a flashing LED 80% would be 8 seconds, 60%, 6 seconds. easy enough to see. Or go to 100 second period. \$\endgroup\$
    – Tyler
    Mar 24, 2022 at 19:05
  • 2
    \$\begingroup\$ Have a LED at full brightness next to PWM LED. Have 2 LEDs. One at 100%, the other at 50%. Then your PWM. Which is brighter? \$\endgroup\$ Mar 24, 2022 at 19:36

1 Answer 1


Two ideas from some colleagues that I really liked:

  1. A fan pointed upwards, blowing on a ping pong ball so the height represents duty cycle.

  2. A servo or solenoid holding a window so it can allow LEDs to be shown.

The suggestions in the comments don't meet my requirements (which I didn't necessarily share, to be fair), because:

  1. Long period PWM defeats the purpose of PWM IMO.
  2. Two LEDs would work but the difference would still not be that noticeable.
  3. The wheels don't use the PWM system, which is the actual thing we want to show off.

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