justjohn:
Looking at the relay board, I'm guessing that the multi-pin packages on the board are either fets or transistors, so is likely fine being driven directly off the arduino - that not being any part of the problem.
Hi @justjohn, yes I agree about the interruptor = switches and inductive loads.
I haven't had a good long look at the interrupter data sheet, but it may be possible to turn the zero crossing feature off, I may be wrong.
The relay PCB does not need a lot of current as you have noticed with their input circuitry, they are designed for direct drive from microcontrollers.
No problems with your added comments, that is why its a forum, its 3:40am here, I'm just waiting for hayfever medication to kick in, then I'm hopefully back to sleep.
Tom... 
