can someone explain to me how a relay works and what its used for?
thanks

 

The dumbed down version is it's an automatic switch if an event happens.

So for example if it detects 12V on a line it can either open or close a circuit. Same thing if it detects a ground.

With this generic of a question you should just go to wiki....

 

I believe I remember reading about this that it's used to have a small voltage/current (sorry ... never was an EE) provide a switch for a larger voltage/current.

Example, a small voltage/current from a switch on the coolant temperature switches goes through a relay to switch the much larger current needed to drive the fans.

 

wacii is right, it is primarily used to allow a small current to switch a large current. For example, you wouldn't want the full current draw of your headlights, traveling into the cabin and up to the switch on the dash or steering column. It is a danger if there is a short, like in an accident, and running heavier gauge wire is expensive and bulky.

Thats the basic idea, but you can use them for any number of things. You can even use them to build logic gates, a basic building block of computers.

Here are 2 excellent primers on relays and how/where/when to use them.
http://www.installdr.com/TechDocs/999403.pdf
http://www.installdr.com/TechDocs/999404.pdf


<----- kind of a relay geek, and a semi self taught electronics guy.

 

thanks alot. that makes it very clear