quick relay question Options

[lagos]

Im hooking up a relay. I have these wires..

White
Black
Red
Yellow
Blue.

From my understanding, white and black are for the magnet that "flips the switch, and the rest of the wires get hooked up based on if you want the relay to be NO or NC.
I wired the white wire to power. However, when I put a multimeter to the black wire (that should hook up to a ground), I noticed that i also get 12v there. This is normal right? I can just send that to a ground without issue to make the relay click on, right?

This post has been edited by lagos: May 30, 2008 - 5:15 PM

[BloodyStupidDave...]

Im hooking up a relay. I have these wires..

White
Black
Red
Yellow
Blue.

From my understanding, white and black are for the magnet that "flips the switch, and the rest of the wires get hooked up based on if you want the relay to be NO or NC.
I wired the white wire to power. However, when I put a multimeter to the black wire (that should hook up to a ground), I noticed that i also get 12v there. This is normal right? I can just send that to a ground without issue to make the relay click on, right?

Probably. The "magnet" is actually a big coil of wire around a ferrite core. When a current flows through the coil, it creates a temporary magnetic field which then (typically) attracts some magnetic metal attached to a contact, causing the contact to close:

link 1
link 2
link3

To be sure, you sould disconnect the white again temporarily and put the multimeter into resistance (ohms) mode. Touch the red and black leads of the multimeter together and note the reading. Now touch the red multimeter lead to the white lead from the relay and the black multimeter lead to the black lead from the relay. The value should be higher (a few ohms). This confirms that there is a very long wire between the two multimeter probes - that coil.

This post has been edited by BloodyStupidDavey: May 30, 2008 - 5:33 PM