Relay integration

[Boring]

Do you also need a diode when using a solid state relay?

You need a protection diode anytime you are driving an inductive load (um, it has a coil as part of the load).

I'm not sure what you mean by solid state relay... if its a power fet or some other solid state device like that, then no, you don't need the diode protection.  The protection diode is only for going across a 'coil' to alleviate the back EMF that might otherwise destroy your Pine board. 

Some relays are in a solid block (they look solid state) but are inductive loads... and these need the diode protectors.  Again, many relay driver boards have the diode built-in, so check the data sheet of the boards you purchase ...

Using a board in between your CPU board and the load is a great tip. Some years back I used a Panasonic AQA211VL 
https://www.panasonic-electric-works.com...en_aqa.pdf

I used it directly on a Arduino Uno without diode or intermediate driving board. Guess I was lucky I didn't blew the Arduino.

Tanks again for the great tip. It is something I will definitely use in the future.