# What is the difference between dimmable LED bulbs and non dimmable?



## dspiffy (Apr 20, 2014)

Is it the LEDs, the power supply, or both? If the power supply, what specifically is different?


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## caddylover (Apr 20, 2014)

dimmable LED's have a control circuit that allows the use of varying voltages. The LED's are the same, how they react is determined by how they're driven.


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## dspiffy (Apr 20, 2014)

The control circuit is part of the power supply? What differs from a normal power supply?


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## Dave D (Apr 21, 2014)

Deleted.


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## dspiffy (Apr 21, 2014)

Wait, battery? I'm talking about 120vAC bulbs.


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## inetdog (Apr 21, 2014)

The difference is that instead of simply regulating for constantly current through the LEDs, the driver is built to respond to either lower voltage or to phase triggered waveforms by lowering the current to the LEDs.
There is a choice to be made between using a simple circuit that will deliver uniform output despite line voltage variations and a more complex circuit that will allow one or another type of dimmer to work at the expense of variable performance when you are not trying to dim.


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## dspiffy (Apr 21, 2014)

Thanks, that's the best explanation I've heard so far.


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## Dave Ecklein (Feb 19, 2022)

What about table lamps that have just one level of dimming by using a rectifier for the dim switch setting? Will these work with a dimmable LED replacement bulb?


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## JustAnOldFashionedLEDGuy (Feb 20, 2022)

Dave Ecklein said:


> What about table lamps that have just one level of dimming by using a rectifier for the dim switch setting? Will these work with a dimmable LED replacement bulb?



Not normally no. I had a range hood that was like that tried a few dimmable bulbs I had around. They all output 100% on either setting. This was as expected. I modified the range hood.


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## Chauncey Gardiner (Feb 20, 2022)

The last time I purchased dimmable bulbs I called the 800 # on the bulbs and asked what dimmer switch would function properly with their bulbs.


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## lightfooted (Feb 20, 2022)

Chauncey Gardiner said:


> The last time I purchased dimmable bulbs I called the 800 # on the bulbs and asked what dimmer switch would function properly with their bulbs.


And???


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## Chauncey Gardiner (Feb 20, 2022)

lightfooted said:


> And???


 
The person on the other "end" of the phone informed me none of the Home Depot dimmers would function well with their bulbs. This was at least four years ago. I purchased some of the first LED bulbs Cree released for sale. Since then all of them have been replaced with newer offerings. Most recently I purchased a dozen from Prometheus Lights. I love them but three of the 12 have been problematic. One of the issues of being an early adapter.


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