This page is everything you wanted to know about relays. What
they are, why and when you want to use them, how to use and wire
them, and stuff like that. What's a "relay"? It's a electrical
device that functions something like a wired remote control
switch. Instead of having the switch you push/flip/whatever do
the work of supplying power to whatever you wanted it to, you
have it control a relay which then does the real on/off
switching work. That's it. It's really not very complicated, now
is it? A mechanical relay does this through the use of an
electromagnet - a magnet that is only "on" when there's power
running through it - that pulls a set of spring loaded contacts
to make or break the connection and achieve the on-off effect.
This is called the "coil" or trigger wire - the other wire
coming out of the coil is connected to ground. Whenever you
apply power to the other coil wire (the trigger), the relay is
on. As soon as power to this trigger is turned off, the relay
turns off. Simple, huh? There are als