Why are dimmable LED lightbulbs not suitable for use with dimmers?


Why are dimmable LED lightbulbs not suitable for use with dimmers?

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LED lights do not dim in the same way as traditional incandescent lights. With at traditional incandescent dimmer it will gradually reduce the amount of electricity flowing through the circuit and as a result through the filament of the bulb, reducing how brightly it glows. But an LED only functions properly in a fairly narrow band of current, instead achieving dimming by being switched on and off extremely quickly. If done rapidly enough the human eye cannot tell it is flickering and instead just perceives the average amount of light being produced. If used with a traditional dimmer the LED will just abruptly stop working when the current becomes insufficient.

Two different things going on here.

Dumb, dimmable bulbs can be used with dimmers no problem.

It’s the smart bulbs that can’t be used with a dimmer. Smart bulbs have a little computer in them that controls everything in it (color, brightness, etc.) and that computer needs the normal voltage to operate properly. A dimmer cuts the voltage (less voltage equals less light) so that can cause issues for the little computer.

Smart bulbs use their own internal dimmer controlled by the little computer. There’s no need for a hardwired dimmer switch, and it’s just asking for issues if there is one.

LEDs work different from incandescent bulbs. (that’s the shortest answer)

Incandescent bulbs are a piece of metal sealed in a glass bulb filled with non-burning gas. It then has enough electricity ran through it to basically burn the metal, but because the gas doesn’t let that happen, it just sends out light and heat. It also lasts much longer because it isn’t burning, but it still is eventually used up. If more electricity goes through it, it ‘burns’ faster and brighter. If less, then it ‘burns’ slower and dimmer. This is how a classic dimmer works.

An LED is a diode (piece of metal/semimetal/plastic that only lets electricity through in one direction) that emits light the moment enough electricity goes through it. It can’t take much more electricity, or it melts. It can’t take much less electricity, or it just stops emitting. There is a small range that more/less electricity means more/less light, but it is too small to be really useful. So the classic dimmer’s method of “just use less electricity” doesn’t work for this “threshold” type of light.

Regular dimmers use a simple electronic circuit which powers itself by stealing a bit of power from the bulb. They require a certain bulb power to work otherwise the dimmer’s share isn’t enough to power the circuit and it doesn’t work right – the bulb flashes or pulses instead of dims.

More advanced dimmers use a better circuit which is more complicated but is able to work better with low power bulbs.

There is a separate problem with LED bulbs which is that they contain an electronic regulator to ensure that the Leds light at the correct brightness. These expect a specific voltage and will malfunction if you use a regular dimmer.

Dimmable LED bulbs contain a modified regulator which is able to detect the action of a dimmer switch, and automatically adjust to a dimmer mode when it detects a dimmer altering the power voltage.