I simulated this circuit in multisim. It is working fine. However, I am just curious to know if it is possible to drive multiple loads with multiple opto-isolators with single TRIAC? Something like this: Sorry for the rough drawing. Is it understandable? All loads are parallel to the TRIAC.

I am going to put arduino instead of that +3V.


  • \$\begingroup\$ I don't see multiple loads in your second schematic, only multiple optos. \$\endgroup\$
    – brhans
    Sep 3, 2018 at 9:09
  • \$\begingroup\$ I forgot to state that! I have re-uploaded it. \$\endgroup\$
    – Parth
    Sep 3, 2018 at 9:14
  • \$\begingroup\$ There are two different identities (numbers 157724 and 73158) called Transistor in this group, see the answer to this question. \$\endgroup\$
    – Uwe
    Sep 3, 2018 at 9:41
  • \$\begingroup\$ I realized it just now. Should I change it? Are mods ok with it? \$\endgroup\$
    – Parth
    Sep 3, 2018 at 9:48
  • 1
    \$\begingroup\$ You would not make two live connections to the circuit. Similarly all the loads would connect to the same neutral. By the way, I'm the real Transistor. \$\endgroup\$
    – Transistor
    Sep 3, 2018 at 16:51

1 Answer 1


You can switch that one triac with multiple optos. The leakage current will be multipled by the number of optos so you might want to adjust R3 downward to compensate (read the datasheets and calculate the worst case gate current leakage at maximum opto temperature).

The triac will turn on when any one of the optos is 'on', so it's kind of a power 'OR' gate.

The one triac can switch multiple loads in parallel with each other, all on and off at the same time, of course.

It's probably better to combine the signals on the LED side of one optoisolator unless you have some motivation for isolating those signals from each other. A simple 74HC NOR gate will work well if the signals share the same power supplies.


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