I am trying to control home devices using a microcontroller and a TRIAC. For switching, I intend to use an optocoupler and triac-based circuit. The circuit is given below (also plenty are available on the internet, but all are the same). enter image description here

The question I want to ask is how much power load I can connect to it's terminal because I need to connect a 230V-50A device at its output. So will this circuit, switch On/Off that device.

  • \$\begingroup\$ Consider using devices which integrate the isolator and the triac like: MOC302 \$\endgroup\$
    – stowoda
    Commented May 10, 2019 at 5:29
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    \$\begingroup\$ 50A is near the limit for Triacs. High current designs often use back-to-back SCRs. IMO, you are also past the power limit where hobbyists should be. I have worked with high power stuff, and this is past where I would play with at home with discrete parts. If you can afford them, there are high-power Solid State Relays, these are more suitable for home hobbyists. digikey.com/product-detail/en/carlo-gavazzi-inc/RM1A23D75/… \$\endgroup\$
    – Mattman944
    Commented May 10, 2019 at 7:52
  • \$\begingroup\$ @Mattman944 - I have opened one of these and they contain a triac + opto inside. Is there any benefit in buying these? Is your experience better than mine? \$\endgroup\$ Commented May 10, 2019 at 14:55
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    \$\begingroup\$ @Whiskeyjack - Lower power modules will have a triac. Higher power modules like the one I referenced will have back-to-back SCRs. This module also has built-in zero switching circuitry (option A). The main benefit is safety, IMO inexperienced people should not be designing with high voltage, high current. You may be working with exposed high-voltage for a week while you try to get this to work reliably. Then if you are not careful, you will have a giant electrically hot heatsink. High-voltage at a few amps is different, that you can most likely get working quickly, minimizing the safety risk. \$\endgroup\$
    – Mattman944
    Commented May 10, 2019 at 15:34

2 Answers 2


You need to provide more info. I feel you are misinterpreting the situation at hand. Assuming you are right, you will run into other problems than the circuit:

1) Supply: I could find only 4 triacs which meet the current requirements:


2) Heating: 50 A is a lot of current. Triacs will have a voltage drop across them when conducting. Approximately 1.3-1.6 volts. At 50 amps, you will be dissipating a minimum of 1.3x50 watts = 65 watts. This is a lot of power and you will need beefy heat-sinks with active cooling to get rid of this heat.

This video shows a guy making heat sinks for high wattage LEDs. Your case is more severe because LEDs convert some power to light. In your case, whole power is being converted to heat.

I read your comments on the other answer. No, R and C values are not the only difference when you are controlling 10 vs 50 amps. Snubber design is a topic in itself. However there are many things to take care of, especially the triac ratings and thermal design of the entire setup.


I want to ask is how much power load I can connect to it's terminal because I need to connect a 230V-50A device at its output. So will this circuit, switch On/Off that device.

Broadly saying yes, it will switch on and off the load.

The above is a standard TRIAC driver circuit. You need to select the TRIAC and snubbed circuit as per the load current, voltage and the nature of load.

  • \$\begingroup\$ Means if I am controlling a 10Amps load or a 50Amps load, the only difference between their circuits would be values of R and C of snubber circuit. So how do I select their values ? \$\endgroup\$ Commented May 10, 2019 at 5:27
  • \$\begingroup\$ No, 1. important thing is you need to select a rated triac, 2. Select the gate driving resistor and driver based on gate characteristics. 3. select the snubbed circuit based on load characteristics. I am saying the approach will, be common.. you need to re-design everything from scratch by following the application note of that particular triac and driver \$\endgroup\$
    – Electron
    Commented May 10, 2019 at 5:34

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