Grounding

I'm having a bit of an issue with either an eletronic pulse going through the air or possibly power leakage. I dunno which one or how to describe it but i'll do my best.

I have a setup where i'm connecting 24V solenoids to a relay board that is controlled by an arduino. When I flip the switch to turn the transformer off after its been on it is making the arduino do very strange things. Ex. Its blanking out my LCD Screen.

The solenoids are completely isolated to the transformer and the relay board, the relay board is a solid state and there should be absolutely no connection going to the arduino. So why would it be affected by the transformer turning off. The transformer is located in a metal box by itself, not near the arduino.

The transformer is a bell transformer.
Input: 120V AC
Output: 24V AC

Thanks,

  • B

You need to do a process of elimination by altering things one step at a time:
*Disconnect the relay board from the Arduino . Fixes it ?

*Try powering Arduino a different way ( e.g. Battery). Fixes it ?

Etc ... this should identify the area that is creating a problem . When you turn a transformer on or off it can generate quite a spike in the supply. If it seems mains bourne some form of mains filter might stop it.
If the relay board is solid state , is it optically isolated ? That would help too

PaulHammy:
You need to do a process of elimination by altering things one step at a time:
*Disconnect the relay board from the Arduino . Fixes it ?

*Try powering Arduino a different way ( e.g. Battery). Fixes it ?

Etc ... this should identify the area that is creating a problem . When you turn a transformer on or off it can generate quite a spike in the supply. If it seems mains bourne some form of mains filter might stop it.
If the relay board is solid state , is it optically isolated ? That would help too

The solid state relay board is "Phototriac" isolated. So if i'm correct that means its optically isolated from the 24V going to it. (I'm not very good at electrical engineering, so do please correct me if i'm wrong)

I did disconnect the ground from the solidstate relay board to the arduino but no change. I changed the power to USB power coming from my laptop with no connection to the mains from my laptop and no change.

I did some research yesterday about using capacitors to filtering power to a motor but would a capacitor help in my case? and if so where would the capacitor be needed? Going to the transformer or going to the arduino?

A link to the relay board can be found here. Amazon

I'm honestly clueless... Is there a way for me to ground the arduino to the mains? I have the arduino power in, and return line connected to the power supply (when in use). but I have a third prong for i'm assuming the actual ground. Like I said i'm no electrician by any means so if i'm completely shooting in the dark on this then I understand...

Many relay boards have the option to opto-isolate, but you only get the isolation if you have a
separate supply to power the relay board and remove the jumper that allows powering the
relay board from the Arduino 5V.

You can verify isolation with a multimeter, disconnect everything but the cabling between Arduino
and relay board, then test for continuity between Arduino ground and 5V and the relay board's
power rails (the ones that power the transistor switches, not the opto coupler input LEDs!)

MarkT:
Many relay boards have the option to opto-isolate, but you only get the isolation if you have a
separate supply to power the relay board and remove the jumper that allows powering the
relay board from the Arduino 5V.

You can verify isolation with a multimeter, disconnect everything but the cabling between Arduino
and relay board, then test for continuity between Arduino ground and 5V and the relay board's
power rails (the ones that power the transistor switches, not the opto coupler input LEDs!)

Right, I had read that as well so I already had a power supply specifically setup for the relay board to completely isolate it from the arduino.

I also tried the condutivity test and the only conductivity I could find was from the ground from the relay board to the ground on the signal side of the relay board. Is this correct?

Theoretically if I have the ground (signal side of the relay board) connected to the ground on the arduino that would pair the grounds thus not isolating the arduino. but I tried this with both the ground connected and unconnected and no change.

Did you remove the jumper between "VCC" and "JD-VCC"?

Chagrin:
Did you remove the jumper between "VCC" and "JD-VCC"?

I don't believe the solidstate relay board has one. I know the mechanical relay one does, but I don't see one on this board.

The problem is that the AC coil is suddenly being disconnected and the collapsing magnetic field is generating an electro magnetic pulse. This is then interfering with the Arduino. Do not attempt to do any grounding, this is not the problem and could be dangerous.

I did some research yesterday about using capacitors to filtering power to a motor but would a capacitor help in my case? and if so where would the capacitor be needed?

Yes what you need is called a snubber circuit, across the solid state switch, so in series with the coil.

Grumpy_Mike:
The problem is that the AC coil is suddenly being disconnected and the collapsing magnetic field is generating an electro magnetic pulse. This is then interfering with the Arduino. Do not attempt to do any grounding, this is not the problem and could be dangerous.
Yes what you need is called a snubber circuit, across the solid state switch, so in series with the coil.

Snubber - Wikipedia

Yeah I ended up finding out it was flooding the transformer (AC converter) to the relay board; Like you described above. Not quite sure I fully understand how to fix this though. You say I need to create a snubber switch to the solid state switch in series with the coil. Which coil are you referring? The 24V transformer?

The 24V Transformer is AC, where my transformer (AC converter) is DC.

We are planning on having the transformer in a separate box anyway, so shouldn't that keep any electromagnetic pulses out?

Last question, The snubber circut that you posted uses a resistor, switch, and a capacitor, but how do they intertwine with the solid state relay board? the resistor/capacitor I get but where does the switch come into play?

The 24V Transformer is AC, where my transformer (AC converter) is DC.

Sorry that doesn’t make sense.

Is the solenoid being driven by AC - I am assuming so because otherwise you couldn’t switch it with a solid state relay.

The snubber is a circuit that will reduce the rate of change of current in the solenoid. So it goes across the switch that is controlling the solenoid, like it showed in that link.

I think you better post a schematic of what you have wired.

Grumpy_Mike:
Sorry that doesn't make sense.

Is the solenoid being driven by AC - I am assuming so because otherwise you couldn't switch it with a solid state relay.

The snubber is a circuit that will reduce the rate of change of current in the solenoid. So it goes across the switch that is controlling the solenoid, like it showed in that link.

I think you better post a schematic of what you have wired.

Yes the solenoid is being driven by AC. However when I plugged the transformer into a different outlet it didn't happen. So wouldn't a snubber powering the relay board be a fix?

Schematic here:

Blade2021:
Schematic here:

That link doesn't work for me.

My apologies, I've had these linking issues with dropbox. They don't like to share to websites to embed images. Kinda annoying, I re-uploaded it to google instead. This one should work.

The digital pin numbers might not exactly match the schematic and there is no more connection of ground between the ground next to the signal pins on the relay board and the ground to the arduino.

EDIT:
Would a 5V voltage regulator work? Going from the power adapter to power the relay board with a voltage regulator in between?

Blade2021:
This one should work.

Nope. That's still an "Error 403 (forbidden)" for me. So still not properly shared publicly.

If you are logged in to your google account then you might see the image, but others not necessarily so. A good test when uploading files for public consumption is to log yourself out of whatever account you are using for that particular service, (be it google or dropbox or whatever), then clear your browser cache and reload the forum page and see if your link still works.

Read this image guide

See Attached.

What is the components marked S1 to S7?

Also why does your relay on the schematic have a normally closed output where as the relay module posted does not have one. In fact there is no solid state relay that has a normally closed output.

Grumpy_Mike:
What is the components marked S1 to S7?

Also why does your relay on the schematic have a normally closed output where as the relay module posted does not have one. In fact there is no solid state relay that has a normally closed output.

S1 to S7 are optic sensors.

I use it in my schematic but I don't show any connections to the N/C due to that fact. It was the only part that I could find for Fritzing.

was the only part that I could find for Fritzing.

That is one of the big problems using Fritzing. When this happens then you are supposed to make your own component, but people don't.

Why is pin 15 of the relay board connected directly to the mains?

mmmm... I don't see a pin 15 on the relay board. The only two components with #15 pin would be the arduino or the LCD. I followed the arduino pin 15 to a output of a sensor which would be below 5V at its highest.

EDIT:
The only connections I see to the mains for the relay board are the vcc and gnd. The power adapter I have is only supplying 5V to the relay board.

But I did try a voltage regulator and it still messed with the LCD. BUT! the voltage regulator is only going to the relay board not the arduino.