Difference between using relay alone or relay module

I’m using and arduino nano to control computer fans at 12v using a relay module, the circuit is working fine.

But I also need to control some other things and there are too much cables now, so I’m designing a pcb to make a cleaner circuit. It seems easier to add the relay alone to the pcb and not the ones that comes already in a board. Is there any risk or disavantage when using the relay alone ??




The Arduino I/O ports can't put-out enough current to directly drive a relay coil. You need a driver circuit. (And, the relay you showed has a 12V coil.)

However, if everything is switched together you can drive one or more relays from the relay board (module). And, if that relay board is switching 12V you would want the other relay(s) to have 12V coils.

You cannot use the relay “alone”. You need a transistor - or better, a FET - to drive it. If a transistor, a series base resistor, if a FET, a pull-down to ground.

You need a bypass capacitor - 100 µF electrolytic - adjacent to the relay and switching transistor with the “kickback” diode between the bypass capacitor positive and transistor collector (drain) so that the relay connects across the diode.

Using the relay "by itself" is OK, as long as you add a couple if additional parts.

Or use tpic6b595 chip to drive up to 8 relays directly. Only 3 wires/Arduino pins needed. If you need more than 8 relays, cascade more tpic chips. No more wires/Arduino pins needed.

Or don't use relays. (This is the 21st centruary, you know!) If all your devices are 12V, depending on the current they require, you can drive them directly with the tpic chip, or use logic-level MOSFETs such as irl520 or stp16nf06l.

I'm using and arduino nano to control computer fans at 12v...

I always use 4-pin computer fans.

So I can connect the PWM wire of the fan directly to an Arduino PWM pin.
No relays, no mosfets, no nothing.

Thanks to all !