I'd like to make myself a lighting control that would schematically look like this:

enter image description here

I don't know a lot about dimmers, but I heard they have some parameters which might prevent them from working. I'd like to have three dimmers, two of which would control their own branch of lamps (incandescent only, I hate all other lamps atm), and the one that would control both. I assume all dimmers have an option that completely cuts power, because I need that at least on the main dimmer (leftmost on the picture).

What kinds of dimmers (exact parameters are welcome) do I need to use with a maximum of five (on each branch) 75w incandescent lamps?

I wouldn't like this question closed, so I'm adding that this should not only work with exactly (5 + 5) × 75w incandescent lamps, but a maximum of that quantity to include all variants with less lamps, as I believe it should work with equipment required for maximum load (but I am prepared to be corrected on that).

  • If the main dimmer is at half, and the 'sub-dimmer' for branch #1 is full, what power do you want the lights on branch #1 at?
    – Aaron
    Jan 23, 2013 at 23:15
  • See also diy.stackexchange.com/q/4425/80
    – Jay Bazuzi
    Jan 24, 2013 at 2:15

2 Answers 2


You could get pretty close to this with three Insteon switches set up:

  • Switch "A" (the master) connected to line and neutral, load lead capped.
  • Switches "B" and "C" connected to line and neutral, with the load (light bulbs) connected to the load lead and neutral.
  • Create a scene where switch "A" acts as the controller, and "B" and "C" are responders.

Switches B and C will operate independently, but any action at A (on, off, bright, dim) will affect both of them.

Edit: @Matthew PK reminds me to point out that this could be any scene-capable smart switch.

  • 1
    +1 This is the answer: to use digital "smart" switches with scenes. Standard resistive dimmers might work but will likely be unsafe. Triac dimmers will not work.
    – Matthew
    Jan 24, 2013 at 17:59

Commercially available dimmers are not going to play along nicely with other dimmers.

Note that to achieve all possible control over the two branches of lights, you simply need separate dimmers on two completely independent branches.

Two separate dimmers will not provide a master control, but suppose that the dimmers are digitally controlled. Then the configuration of having a master dimmer and two branch dimmers can be simulated in software.

For example, see this video showing an Insteon dimmer being controlled by a script from a PC.

  • Reading this answer I'm left with the impression that the Insteon solution would require a PC to work. This is not true. The solution using three Insteon switches can be programmed and put to use without any PC involved.
    – alx9r
    Jan 24, 2013 at 4:02

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