Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I am building an AC dimmer circuit to control from an Arduino using this schematic:


I need to make this dimmer so that it can be used as a three way switch as well. How would I modify this circuit to work in place of a three way switch?

share|improve this question
Do you mean that you want to control three light bulbs independently? – Cornelius May 18 '14 at 19:23
Or, do you want three separate switches controlling one lamp? – Andy aka May 18 '14 at 19:24
No, I want to have two switches control the same circuit. I.e top and bottom of staircase – user43028 May 18 '14 at 19:25

I would have both switches connected to the Arduino, with the Arduino firmware allowing both switches to control the same dimmer.

For this to work, you would have "bright" and "dim" switches at both control points, rather than having a pot somewhere to control the dimmer. (For bonus points, you could have rotary encoders at both locations, rather than switches. :-) )

share|improve this answer

Here's what a three way switch circuit looks like: -

enter image description here

If you only need two locations then omit the more complicated DPDT in the centre: -

enter image description here

Should it be that you want the switches going to the MCU then please note that they enact the logical ex-or function.

share|improve this answer
ok, but how would I integrate the dimmer circuit in so that the other switch works if turned off from the dimmer? – user43028 May 18 '14 at 19:29
Put the dimmer anywhere in series with the load OR put two dimmers in the two common lines between the switches; one controlled at one end and one controlled at the other. If you want either end to be able to dim the lamp then you need to wire pots to your MCU so that the correct pot is chosen as "master". – Andy aka May 18 '14 at 19:32

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.