I want to trigger some external relay (to switch on/off 230V devices) with my Raspi and PiFace. So I was thinking of connecting relays to the output pins.
Now there are different types of relays. Most of the I found up to know have 12V primary with 230V on the switching side. Do I need to get another relay now with 5V primary matching the 5V of the PiFace to switch the 12V relay?
Additionally is it ok to keep the relay switched on all the time? I found some relays with 1VA (1W) consuming to keep the 230V powered on. So eigth would consume approx 1VA. Could this be provided by the PiFace?
Sorry for the dumb questions- I'm really a newbie to electronics.