Relay connection PCB for switching 240VAC

Hi there,

I'm looking for a simple sheet for switching a low voltage relay from flash through arduino.

What wasnt clear for me from the previous sheet i found here,that do i need an external power supply for the relay?

MAny thanks,


do i need an external power supply for the relay?

If you use a Solid state relay to switch your AC then you don't need any extra power. The relay just looks like an LED with built in series resistor to the arduino. Check your specific relay to make sure this is true, but it is true for most SSRs.

To expand a bit on what Mike said, look at the datasheet for your SSR. I had a 240V double throw SSR (basically two SSRs in one package, complete with independent digital inputs). The Arduino's output current capacity wasn't quite enough to turn on both of them at the same time; I had to either use two digital outputs, one for each leg, or use an arduino pin to switch a transistor which in turn powered the SSR input.

In either case, the arduino's power supply is more than enough to turn on the SSR, even if a single arduino pin isn't.