explain what a relay is and when to use it

Alright guys, ive been looking up information on relays and when to put them in, and i cant find a explanation on how to hook them up and when to use them. Im trying to get a grasp on it so i can wire up some lights. If you can explain to me please be sure to break it down pretty simple so this marine can understand it hahaha.

 

http://www.danielsternlighting.com/tech/relays/relays.html

Google is your friend

 

So you'll often want to use them with accessories that have high currents. When you wire a high-current accessory through a relay instead of directly through a switch, you’re minimizing the amount of current at the switch. For more in-depth information, see the quote below from @tacozord in his DIY RTMR/Fuse block thread.

Oh, and thanks for your service!

 

Also used to change polarity from Neg to Pos output vice versa, also to break a circuit such as starter disable.
The list is endless. I've used this 12V site for many years now.
http://www.the12volt.com/relays/page1.asp

 

I was under the impression it was against the rules to post a link to another site with no info...

So for the sake of actually having useful info in this thread for someone later on:

A relay in it's simplest form (single pole, single throw) is a coil that, when power of appropriate voltage is applied, moves a switch (the pole and throw action).

On a single pole single throw relay you'll see 4 pins.

Coil (+) -> This comes off the switch you're using to actuate your accessory. The switch should be run though the battery.
Coil (-) -> Direct to chassis ground or battery negative
Load -> this goes to the positive side of your powered accessory. From the negative side of your accessory you'd go to the battery or chassis ground.
Battery (+) -> This is your (FUSED!) power source. Or direct to the positive terminal on your battery.

You'll have to look at the wiring diagram sorta like this:



So you see the coil (which doesn't actually have a "proper" orientation. Power to either side will work). Terminal A can be the "Battery (+)" side. Terminal B can be load. These can be switched depending on how you prefer.

I could draw you an actual diagram with how this would work... one sec.

 

Pardon this absolutely HORRIBLE 5m paint drawing but this should give you a basic light diagram with no fusing and using a single pole single throw relay. Red "lines" show "positive" wire and green lines show grounds.

Top/left is the relay. You see the coil, you see the "normally open" circuit.
The yellow penis is the "light"
The middle "normally open" line would be your switch.
Bottom left is obviously your battery.

 

that drawing....it's so bad...and "The yellow penis " made me laugh so hard.

 

TacomaWorld always delivers.

 

Classic! This should be a Christmas card!!!

 

Oh god I just realized that.