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Can someone ELI5 why often lights set up with a dimmer also flicker? (mander.xyz)

submitted 2 months ago by [email protected] to c/[email protected]

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Seen this in many houses, people upgrade their lighting setup and install a dimmer. Which works. But usually it also makes the lights flicker unintentionally, which is super annoying IMO.

Now, my understanding of electrical engineering is pretty rudimentary so I'd appreciate more something that explains the concept in a way that Cavewoman Mothra can understand rather than something technically accurate.

Thanks

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[–] [email protected] 11 points 2 months ago* (last edited 2 months ago)

Well written.

I think an important concept to introduce is Pulse Width Modulation, or PWM for short.

Normal AC Power coming out of wall looks like a sine wave, in that it smoothly cycles between +110/240V and -110/240V. This means that 50% of the time the voltage is positive and 50% of the time the voltage is negative.

PWM usually deals with signals which are either entirely on or off, with no transiton between them. This way, you can vary the amount of "power" delivered by varying how much of the time the signal is on and how much of the time it's off.

Dimmers usually modify the sine way in a way that tries to accomplish the same thing, by chopping up the signal to make the effective "on" time be shorter than 50%.

With non-dimmable LEDs, this messes with the AC to DC circuitry in the lamp in the way slazer2au says, because the lamp doesn't retain enough power between two on-cycles to stay on.