AC Light Dimmer


I was making a light dimmer for light regulation. It’s supposed to be running on 230V 50Hz mains and designed to handle 8 amps. Design is classic that can be found in triac or optocoupler design guidelines ( It should support also inductive load because I have plan to use same circuit to regulate thermoelectric heating heads (that’s why there is additional resistance and capacitor).

I would be grateful if someone would make a review of the circuit. It’s always good to be sure when working with mains. :slight_smile:

Also suggestions what capacitor to use are welcome!


Dimmer Module by vexfalard 17aeed03144f3d19 - Upverter


One of our in-house HW engineering experts can take a look at the design. We’ll keep you posted. Thanks for sharing it here.


Hey there,

We consulted some experts on this type of circuit and they came back with the following feedback. Much if the circuit looks good! ([OK])

  • [OK] Topology of snubber circuit for inductive loads;

  • [OK] The values for the input current surge rating for the input resistor

  •      [OK] The values for the snubber circuit (R2 and C1);
  •      [OK] U1 model MOC3023 for 230Vac;
  •      [OK] LED driver suited to 3.3V logic; (as cited on Readme note);
  •      [OK] Triac Q1 rated for 4A and 8A current;

If you are using a microcontroller to control the dimmer, refer to figure 10 of Fairchild application note to monitoring the zero cross of the AC Line.

In this case, the different grounds can affect the functionality of controller and the proposed solution it’s a method to solve this issue.

Hi vexfalard,
I looked at yout layout and I would suggest you use thick traces for the snubber circuit,C1 and R2, too. They handle high transient current.

Now I see it was 2015. Oh, well.