relay identification

**poppyleigh** · 15-04-2011,10:40 PM

can anyone tell me what relays are for what plz any pics even better

**mrjolly** · 16-04-2011,10:15 PM

ok dude,
a relay is a switch.
in cars there are circuts that pull quite a lot of current. and to switch quite a lot of current you need a switch with bigger contacts than you would need to switch a small amount of current. ie , a bit switch for a lot of power , a small switch will do for a small amount of power.
lots of the controls on your car , buttons you press or operate , or sensors on the engine need wiring. and you want the smallest amount of wiring you can get away with ( to save weight and manufacturing costs ) so the car has lots of small wiring to control stuff. so when you turn your head lights on , they pull quite a lot of power, so the wiring on the switch you press/ turn or whatever to turn your lights in actually turn a relay on, which operate your lights.
a basic relay will normally have 4 contacts.
1 will be a earth connection
1 will be the live feed from your switch
1 will be a live connection from the + of the battery
1 will the wire going to the live feed to your headlights.

how they work is , they have a big contact in them ( switch contact )
and that is switched on by a electric coil, which makes a magnet effect happen and a small bit of metal is pulled by the magnet effect and that closes the contacts, when the power is turned off to the coil a spring pushes the contacts apart.
the coil is permantly earthed, you switch the live to the coil ( very small amount of power needed so small buttons and wiring needed ) and the relay carries the power to big stuff.

bet you wish you never asked!

well me anyways