relay module board, do I need resistor and transistor ?

Hi, I am kinda new. I bought a 8 relay board module. see

I have seen schematics that have a resistor and transistor in the connection between the arduino output pin and the module in pin.

Do I need those or because this is a module, and it looks like it already has those things in it, I can hook it directly from arduino to module ?


It's opto-isolated from the looks of it, you just drive the opto coupler - you need
to know if it has resistors on the input or not.

There are resistors. You don't need anything else. has a schematic for these opto-isolated boards if you're interested.

To get isolation, use a separate 5V supply for the relay module, remove its jumper and do not connect any ground wires from the relay module to the Arduino.

No resistor or transistor required - just directly connect IN1-8 to Arduino outputs.