I have a 220V to 12V 500mA transformer+rectifier plugged into my wall socket, that drives a pair of relays. I've put protection diodes on the relays. However I still have a 500v kickback into the mains when I turn off the power.
How am I supposed to fix this? Using a varistor/TVS or something? Do I connect it across the mains before the transformer? Can someone suggest a specific part that I should use?