I want to switch on/off some AC device using solid state Omron G3MB relay I know that for magnetic relay there should be transistor and flyback diode, but what about SSR? Can I connect it directly to arduino digital pin without any transistors and anything else?

In a closer look on special arduino module, we can see some extras. Are they necessary? I want to put solid state relay (not separated module) into my custom PCB, and I'm confused about that extras.

Arduino module

  • yes, that's the idea; it's just a resistor and an LED as far as Arduino sees.
    – dandavis
    Commented Nov 23, 2020 at 20:18
  • Mate, according to the datasheet you provided it's safe to hook the arduino, but to be safe put a resistor in between, just to be sure the SS relay don't pull up to much current from the Arduino, as this may casue harm to your device.
    – k.Cyborg
    Commented Nov 24, 2020 at 4:49
  • @k.Cyborg am I misreading the datasheet? The way I read it, there are multiple (sub-) models of the G3MB. Some of which don't require a resistor, but some do.
    – Gerben
    Commented Nov 24, 2020 at 14:55

2 Answers 2


According to the datasheet there are multiple models.

Some already have an input resistor for the led (in the opto-isolator) inside the package, but some don't. For the ones that don't have a resistor inside, you'd need to add one yourself, to limit the current to around 10mA.

Some models also have a snubber circuit inside the package. The need for this depends on what kind of load is connected (inductive vs. resistive (AFAIK)).

I thinks the green thing, in the picture, is a fuse. On the other side of the SSR you can see and indicator led, transistor, and 3 resistor (one to limit current to the SSR, one to limit the current through the indicator led, and on for the base of the transistor.). They probably use a transistor, because the current for the SSR and the indicator led combined, is to high for certain micro controllers.

  • the transistor is likely used as a current limiter for the ssr's led, just like commercial fotek et al.
    – dandavis
    Commented Nov 24, 2020 at 20:06

The answer is a qualified yes. In this case the relay is optically isolated from the load so there is no cross conduction. You need to connect the relay to the Arduino power +5 and Ground supply. I would not connect more then one to any arduino pin as the relay has a max requirement of 20mA. Not all SS relays are the same so you need to check there specs if you use another one.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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