Help with a Relay Module

Projects General Guidance
1

Hello, I need a little help with the wiring of my relay module. I already searched and couldn't find the answer I need, but there's similar questions, so I'm pretty sure it's possible.

I'm automating a fogponics tower and need to switch the pump, fan and mister on and off. Since the mister is 24v, I went with everything 24v on a 6s li-ion setup (with BMS obviously) and connecting the arduino using a step down converter (https://www.aliexpress.com/item/1888459743.html)

Now I need help triggering the relay coils. I have this module:
https://www.aliexpress.com/item/1005002617199944.html

It has VCC, GND and 4 IN ports. I need a little advice in how to connect it... to me sounds logical to connect VCC to +24, share GND between the arduino and the battery (pre and post step down) and just feed a logical port into the IN ports, but I'm not sure if it's safe for the components. Should I add a diode in the GND to the arduino? a resistor? Should I just use battery VCC and GND? Should I add a transistor (mosfet?) to feed the IN port with 24v directly? if so, what else is needed in the circuit?

Should I just buy a 5v module and connect directly to the arduino VCC?

Thanks for reading, and sorry for the basic question.

2

The relays should still be 5v logic to activate them but I would still use a transistor buffer just to be safe.

3

This topic starts gives a picture: Relay module effecting Arduino.

If the relay is a 24V relay (read the print on the relay itself, you need to use an external 24V supply instead of the shown 5V external supply. Be careful, one mistake will kill your Arduino,

4

  • Yes and no.

  • It is best to stay with 5v, however, never connect 5v on the Arduino to power inductive loads.

5

Thanks for the answers. I'll just make the test with shared GND (I just checked the step down and the IN- is connected to the OUT- in the PCB, so they are shared anyways, clearing my main concern to test it)
Everything point that with 24v VCC, the output of a logical port of the arduino should be enough to activate it the relay...

Thanks for the answers, and if it doesn't work, I guess I'll need help with the transistor circuit :slight_smile:

6

If the Arduino's digital pins aren't enough to trigger the relays, then just get a 74HC365 Hex buffer.

7

You don't need transistors.
Remove the H/L jumpers from S1, S2...
Connect arduino 5V pin to middle pin between H and L.
Connect arduino digital pin to IN1....
Power the relay at 24V on DC+ and DC-