RC snubber for relays module

Other Hardware General Electronics
1

Hello,

I've built the classic greenhouse control using a relays module. I've had issues with the arduino crashing due to, I guess, "current overload" (I'm not sure this is the correct term) when the relays module is activated/deactivated. I've read that an RC snubber could fix the problem. I bought the classic RC snubber module that is sold on Amazon, can someone explain to me how it is wired to the relays module?
Please note that I just started out playing with arduino and electric stuff so my knowledge is limited.
Additional info: the relays module is powered by a separate USB power supply and the GND are separated. I'm not sure it matters but the wires that go from the board to the relays module are 1.5mt longs.

this is the RC snubber:

image
image522×522 31.9 KB

2

That's likely intended to connect across the relay contacts.

This RC snubber won't solve the problem you're having.
Please post a schematic of your project and let's see what we can come up with.

3

Hi,

As @anon35827816 has suggested a circuit diagram would be essential.
Also some pictures of your project so we can see your component layout.

I hope the 1.5M of signal wires do not share the same route as the power, AC, wires.

Thanks.. Tom...

  • List item :smiley: :+1: :coffee: :australia:
4

Thanks both for your help. This is the schematic:

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image873×535 7.81 KB

Please note that the power strip is the only source of current possible there.

@anon35827816 Could you please be more specific about how to wire the RC?

5

Hi,
io-io25

Place the snubber across the COM and NO terminals.

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

6

Thank you very much!
Do you see any issue with the schematic?

7

Hi,
A hand drawn circuit with pins and components labelled would have been more informative.
What voltage and current are the relays switching?
What are the loads?

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

8

Yes. You have two USB supplies in the power strip, one going to the relay module and one to whatever unspecified thing the "MCU" is, then you have ground and 5 V connecting between the two, so both power supplies are connected together!

9

Thanks. I imagined this could be an issue but I have only one electric socket in the basement. The only different setup I can do would be to connect the arduino power supply directly to the electric socket but I'm not sure this changes things

10

Hi,
How far apart are the MCU and the relay module?

If you have a supply for the MCU and another for the relay module, you do not need the +5V wire between the MCU and the relay module.
You still need the gnd wire.

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

11

They should be around 60-70cm far.

I had a 4 relays module previously and there wasn't a separate GND but 2 separate 5v. I've read that the 5v from the arduino is used to power the LEDs. Anyway I have a 2 relays module with separate GND now, I'll try without the 5v from the micro

12

Hi,
Can you post a link to your relay module please?

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

13

it's this: https://www.ebay.it/itm/353665419304?chn=ps&norover=1&mkevt=1&mkrid=724-128315-5854-1&mkcid=2&itemid=353665419304&targetid=1274925907178&device=c&mktype=pla&googleloc=1008459&poi=&campaignid=9556812461&mkgroupid=128145112008&rlsatarget=pla-1274925907178&abcId=1145978&merchantid=116447982&gclid=CjwKCAjw4qCKBhAVEiwAkTYsPKFs3kyy1umRveqoC47O-wI1BtP6wQQNtZAU0urhOoN62-5w-MgdHxoC28sQAvD_BwE

but I had the same problem with the elegoo 4 relays module

14

That has nothing to do with both USB power supplies sharing a GND.

Also:

I can't make out much useful from the schematic, sorry.

15

ah, now I get what you guys mean. This is the relay module:

image
image1096×1054 115 KB

I've removed the jumper and connected that pin and the GND near it to the USB power. That provides power to the module. The other pins are controlled by the micro and are 5v and GND to the micro and the 2 signal pins that command the relays. So the power should be separated there.

16

better img:

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image1066×784 83.2 KB

17

in the previous module I used, the elegoo 4 relays module, the GND wasn't separate. Unfortunately, changing the module didn't fix the problem

18

OK, to actually achieve isolation with that module, you connect "JD-VCC" and "Gnd" to the 5 V relay supply, and you connect "In1", "In2" and "Vcc" to the Arduino but not "Gnd".

Different module but same circuit:

(And I am not going to say this correction will necessarily fix your problem. :grin:)

19

There should only 3 wires from MCU to relay board, 2 for the trigger inputs and 1 common wire to MCU VCC if relays are triggered by a LOW level or GND if triggered by a HIGH level, NEVER both vcc AND gnd.
Snubber should be across coil, not contacts.

21

Snubber can go across contacts. You meant freewheel diode?