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I recently installed eight recessed LED fixtures and one hanging fixture in my living room. The hanging fixture has three small LED flood/spot lights to illuminate built in shelving on the stone fireplace. All fixtures are currently controlled by a single dimmer.

My problem is that the three small floods are too bright. I've already got the lowest wattage dimmable bulbs available with this G10 style base. Can I wire in a second dimmer in series with the main dimmer, to reduce power to just the one fixture? I'd still like all fixtures to be controlled by the single main wall switch/dimmer but just want the flood fixture to put out less light.

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  • Perhaps try a diode in series with the 110v feeding the LEDs.
    – Yehuda_NYC
    Commented Feb 17, 2016 at 1:06

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No, this really won't work. Suppose you have 2 dimmers at 20% and 50%. You are hoping the effect will be multiplicative, that is, 50% of 20% is 10%. It won't.

Two SCR dimmers in series will, at best, give you the lower dimming level of the two, i.e. 20%.

A PWM dimmer, commonly used on dedicated LED circuits, pulses at its own high frequency. If you have two of them, they will pulse at different frequencies. This will create a much lower "beat frequency", in music this is what makes it annoying when instruments are out of tune with each other. In light, this would look like pulsing or shimmering. You won't like it.

Actual LED emitters can be dimmed very effectively to absolutely any light level. Turn the LED on for 10 microseconds and off for 990 microseconds, you will get 1% brightness - they can be controlled that precisely. It's a lot harder in built commercial products, which have to work with a variety of existing dimmer technologies made for incandescents, and also hit a "price point" that will make you snatch it off the shelf at Home Depot. The result of these compromises is lousy dimming range.

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Most dimmers use SCR (silicon controlled rectifiers) adding a second dimmer should work to reduce just the single lamp. With that said if you turn the first dimmer down two far there may not be enough “gate” voltage to operate the second one but it is worth a try.

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  • Cool thanks. Hope I can find one small enough to mount directly into the base of the fixture.
    – Steveo539
    Commented Feb 16, 2016 at 18:05
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Can you get at the wiring inside the hanging fixture? Try wiring the three small floods in series instead of in parallel. If that works but is too dim you can then substitute higher wattage bulbs.

Of course if one bulb fails then all three will go out...

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  • Yes I can get to these wires. They are crimped together but could easily be separated. Can you wire the LED's in series? If not, I guess I could switch these to incandescent bulbs.
    – Steveo539
    Commented Feb 16, 2016 at 18:05
  • "Can you wire the LED's in series?" Truthfully, I don't know. I was hoping to use you as a cat's-paw to find out.
    – A. I. Breveleri
    Commented Feb 16, 2016 at 20:38
  • Don't wire LED bulbs in series. They have a power converter in them which will be very confused by being connected in series with other power converters. Incandescent in series won't work so well either, the bulbs won't get anywhere near as hot as they are designed to be.
    – greggo
    Commented Jul 30, 2021 at 11:05
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Sure, resistance in series is additive and works as described. But that explanation is irrelevant, given commercially available dimmers do not work by varying resistance. While you may very well be able to engineer a series-combination that works as desired, assembling one from off-the-shelf dimmers would be a long shot.

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This was a fun question for me!

enter image description here

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  • Whoever voted this down obviously doesn't know anything about electricity. If you don't understand something, test it by building this circuit on a board, or pick up a book about series and parallel circuits.
    – Ben Welborn
    Commented Apr 5, 2016 at 12:17
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    Resistive dimming is not used in mains power... There are several dimming schemes, mostly wave shaping, that are cheaper and reduce heat. These systems do not play well with switching power supplies used in CFL and LED dimming, so for LEDs designed for external dimming this quickly becomes a design morass. This is all news to you, eh? Anyway, mains dimmers play even more badly with each other. Your answer is just wrong...
    – Harper - Reinstate Monica
    Commented Jan 1, 2019 at 16:20

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