RC Resistance Surge Absorption Circuit Relay Contact Protection Circuit Electrom

Hello everyone,
I have built a circuit that triggers a few relays like this one

This produces a lot of noise in the circuit and sends false impulses to arduino activating randomnly different inputs, making arduino do weird stuff.
I have done some research and found this product:

This will technically remove the issues, but I am not sure how to install it.
The specification of the product only sais:

When used, the two connectors of the module connect to two contacts of the relay,
or parallel with the thyristor, to avoid induced electromotive force damage the relay or thyristor.

here is a link: STUBBER
Not very clear which contacts of the relay I should connect it to? is it in paralel between gnd and vcc?
Or maybe between gnd and signal for each channel? or between signal and vcc for each channel? or in series on ground wire?... I am very confused.

The snubber is wired across the relay
switch terminals that you are using.

I would check the circuit for the relay board to make sure the opto isolators are connected correctly and operating as isolators. Chances are they are not and that is the reason why you are seeing the issues.

I have never used one of the boards, but I have seen the posts. I made my own with ULN2003/2008 chips which avoids the pitfalls of using someone else’s poorly documented, poor designed and/or poorly manufactured product.

The snubber is wired across the relay
switch terminals that you are using.

So it will be "isolated" from the arduino? how is this going to help with the noise in the Arduino circuit? maybe this is not even the issue, and it is as adwsystems mentioned, a malfunctioning of the solid state isolator that comes onboard with the relays?

Maybe instead of the snubber, a better solution would be a ferrit core?

I don't have an osciloscope, and my electronic knowledge is very limited.

So here is how I know there is an issue with that relay:
I have my arduino conneted through SCL and SDA to a display. it works perfectly, until the relay starts swtiching on/off... it's completely random, but at one point the display freezes and the arduino doesn't respond to any input command... it's like it's stuck.

So maybe it's related to long wires (induction issues), or maybe radio waves created by relay when switching on/off... it is very hard to tell...

I would even take a software suggestion as of how to bypass the i2c error...

or maybe just a flywheel diode will fix the issue?

I believe there is already a diode across the relay. Its likely that orange with black stripe glass component right at the end of the relay.

I believe the issue has a lot to do with your physical wiring. The way grounds are / are not connected and the proximity of the various wires.

Can you share a photo of the circuit where you see this issue?


You are right, it is a "long wire" issue.
I have a buzzer in the system too, connected to one of the arduino pins. If I connect the buzzer close to the arduino, I have no issue, once i connect the long wire that goes through the wall close to other wires (about 30 feet), it freezes the arduino right away, when the first impulse is sent through the "buzzer" pin. And that's just the wire, with nothing connected to the other side (I removed the buzzer completely)... my guess, is that buzzer impulse sent through the wire creates some kind of noise in the SCL/SDA wires...
Any suggestion about how to go about this?... I read something about twisting wires, but I don't know how to do that, because usually I have 2 wires (gnd and 5v) that i can twist together, but all the other wires are signals, like for example a relay, or a sensor, or a buzzer...
I can't put pictures, because it's impossible to take pictures. my setup requires a "control center" where the arduino is, and then all kinds of inputs and outputs spread around the room via long wires. I am using cat5 wires because they are already twisted 2 by 2 and somehow isolated from each other, but doesn't seem to fix the issues.

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