relays

hopefully this can help you. basically a relay is used to activate/deactivate a device when another device is goes to positive or negative.

30- goes to the device you are trying to operate

87a-normally closed, so whatever 30(device being operated) is hooked up to, if you have positive or negative hooked up to 87a, 30 will get that polarity(+/-) when the relay IS NOT active...this wire is usually not in use

87-normally open, meaning when the relay IS active, 30 will get the polarity(+/-) of 87...so if u need 30(device) to get + then hook up + to this wire and if 30(device) needs - then hook up - to this wire

85 & 86- usually 86 is + and 85 is negative... these are the trigger wires...example- if your doors are negative when

open, then a constant supply of 12v+ needs to be on the 86 wire and the door wire would go to 85 to activate the

relay...(then vice versa)...if your doors are positive when open, then a constant supply of 12v- needs to be on the 85

wire and the door wire would go to 86 to activate the relay.

p.s. this may need to be read slowly and twice.

Try this out for size.

http://electronics.howstuffworks.com/relay.htm

Here is a Relay Tutorial for you.

http://www.uoguelph.ca/~antoon/gadgets/relays/relays.html