I have a relay board but I dont know if it has optocoupler built in?

Hi there I have a project for controlling 220v motor. I have the relay shown on the pics. But I am not sure if it has built in optocoupler to seperate 5v and 220v lines. Here I am asking if it includes that? Thank you in advance.

Well it might have one but you have not shown us a good image of the PCB and you have not supplied a link to the module.

Please post a link to where you bought it from

Links to that module, or closer and more pictures please,.

I doubt it, but as noted, from that picture it's hard to be sure.

Sorry but it keeps me blocking adding more than one picture since I am a new user. The best of images I took is below. Thank you! Also I have the link I bought from but it is a Turkish website that does not describe it well and also proposed images are different than what I recieved.

1 Kanal 5 V Röle Kartı this is the link I bought from. A Turkish ecommerce platform. The shown images on the web page is different than what I recieved. They also does not answer my questions because of lack of knowledge. Yes I know I can return it back but I want to make sure if it does not include optocoupler. If it does I will use it.

Most likely that module is using opto coupling.

An opto coupler is a rectangular block with four pins.
So no, it does NOT have an opto coupler.

@burakertr , the relay board on the website has an optocoupler shown, but I think your relay board may have a simple transistor to do the switching (it's not that clear in your photo).

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I do not see any optoisolators. I do see what looks like a FET.


These come in single, double, and quad versions - I always keep a few on-hand. For reasons I don't understand the double and quad versions usually have optocouplers but the single versions don't.

3 Suggestions that might solve the problem for you:

  1. Buy a double version (look for 2 tiny black chips with 4 leads on each one).

  2. Add an optocoupler to your existing relay; they're dead easy to use ... but do remember that the input side contains an LED - so you need a 220 ohm resistor in series if switching to 5V

  3. Consider a solid state relay; no moving parts - handles AC - but generally only a maximum of 2 amps (not sure what your motor draws). Here's a link to one:

Hope this helps.

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This is what you're looking for in locating an optoisolators/coupler

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Unfortunately, your module does not have an optocoupler. It only has a transistor to turn on the relay. Compare the two photos.
Relay without Opto
Relay with Opto

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BTW: Even the optocoupler does not separate the 5V from the 230V (That's what the relay does). And if that is done safely, depends rather on the pcb board design, and on the professional electrician you should consult about questions regarding 230V.

If the relay module has opto isolation or not is irrelevant.
It is the isolation between the three switching pins and the rest of the PCB that matters.

@burakertr can you post an image of the other side of the PCB, the copper track side?

Thanks.. Tom... :smiley: :+1: :coffee: :australia:

Wow, well done, @TomGeorge. Indeed, the optocoupler does not make any sense in this circuit due to the jumper, if you do not use a separate power supply.

The only advantage of the opto is if you have a relay coil that is higher voltage or needs more current than the controller power supply can give.

Tom... :smiley: :+1: :coffee: :australia:

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Thanks to all of you for all the proposed solutions which are all true.

I also thought it does not have an opto isolator like most of you suggested . But one part made me suspicious which is the relay it self. I though relay had built in opto isolator inside of it which I tought was solid state relay because of its look(I did not know what the solid state relay is when I asked the question). But, I still want to learn the type of the relay in the picture, ex; mechanical electronical? As I read on the datasheet it states silver contact relay but I dont think it is mechanical. Is it?

I bought a solid state relay to solve my problem which is opto isolated by its nature that is given in the picture below. Its input is between 3-32v dc and 12.0 mA which can be driven easliy by the arduino. Also, it is suited for driving motor since it allows inductive loads between its ac terminals. Again stating that I plan to seperate arduino and sensors with the motor output by using this solid state relay.

Thanks for all your answers.

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There's clearly no optocoupler on that PCB. Optocouplers are 4-pin DIL packages.