RE: MicroPython #3: PWM, LED Fade

colporteur — Fri, 08 May 2020 15:22:08 GMT

Great technical tutorial.

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During my early electronic training, I was fascinated how human anomalies we taken advantage of. An example is how the frequency of a digital signal can effect the way the eye sees things. If you apply a digital signal with a frequency of less than 30Hz, the LED light will appear to flicker (waveforms A). The absence of light during the off cycle is picked up by the human eye as flicker.

The frequency rate of 30Hz that creates flicker is not a fixed value. Human eyes and brains are unique; Some people may not see a flicker at a frequency of less than 30Hz, and others (me!–Sean) do.

Increase the frequency above 30Hz, the eyes persistence retains the light over a short period of time (waveforms B). The eye sees the LED light on but doesn’t see the LED off because it occurs to fast.

Increase the frequency above 30Hz (waveforms C) and reduce the duty cycle (pulse width), the higher frequency takes advantage of the eyes persistence. The LED is turning on and off but the human eye sees the light on but dimmer.