4 Channel Relay reliability issue


first of all please excuse my english, I am not a native speaker so you may find some incorrect terms.

I am reaching out to the Arduino community because so far I was not able to get something set up which should be very very simple but turns out to have some issues I do not understand.

I have an Arduino Nano (Clone). I would like to attach a 4 channel relay board (like this https://www.amazon.com/SainSmart-101-70-101-4-Channel-Relay-Module/dp/B0057OC5O8) to it and turn the channels on or off to drive 24V.

For the software side I use the default Firmata sketch, but I believe I do have an hardware issue.

First of all I tried to power everything via USB from a Raspberry Pi, so I connected VCC and GND on the relay to 5V and GND on the nano. Then I added four more wires to control the relays to D6, D7, D8 and D9 on the nano.

All went good, but I noticed when all relays are turned on the LEDs on the relay board flicker and sometimes you hear that a relay does not click at all or they click multiple times a second. So I thought this must be a problem with powering, so I powered the whoe setup from a 2A USB wall plug.

This increased the situation, but did not completely solve it. I still found - every now and then - one of the relays (in most cases channel 2 or 3) started flickering… both LED and “click” noises.

So I thought I still might have a power problem, so I set up everything from scratch. Now I have a 24V power supply with 3A which goes into a step down converter, which produces 5V.

I use this 5V power supply to power both, the relay and the nano, USB is no longer connected at the moment, the Sketch turns on the relays once the Nano finished booting. I have attached the wiring I created.

With that set up now the relay channels stay turned on permanently… for a while. Sometimes they are turned on for a few hours, sometimes only for a few minutes, then one of the relays (again in most cases 2 or 3) starts flickering and turning on and off over and over again. That happens for a couple of minutes - then they turn on and all is good.

When a relay is flickering I measured the voltage that comes in at the PIN controlling the channel, the volt meter says 4,9V. I had no further ideas what to check.

I want to use the relay to control heating, so I would love to have a “stable” relay.

My questions:

  • Do you have any idea what is wrong in the wiring?
  • I use Jumper cables to connect Nano and Relay and to provide 5V and GND to the PINs, is that likely a problem?
  • Is there anything else I could check/optimize to make the setup stable?

I really don’t understand what is so complicated with my setup… it seems to be straight forward. But something is wrong.

Thank you!