What is a relay exactly?

I've been going through upgrades and changes I'm going to do and relays keep coming up. What do they do that's so special?

 

Relay is a switch that is powered by a direct power source, but triggered by some other power source.

For example, I put one on the wife's mustang for some pony fog lights. The lights are wired to the relay, so is the battery. But to activate the power, she needs to turn on the headlights (also wired to the relay). When she turns on the headlights, the foglights come on too, then when she turns the headlights off, it un-triggers the relay, turning off the fog lights.

The relay senses that the power to the lights is turned on/off, and switches on/off allowing the battery to power the pony lights.

It creates a completely different circuit so the pony lights don't draw from the headlight circuit (they draw straight from the battery with their own fuse). then when/if a fuse blows, it is only on the headlights or pony lights, but not both.

 

Lots of questions from the soooulpower lately. I am getting suspicious. What do you have up your sleeve asking about relays and stronger 1-wire alternators???:16suspect

 

Another way of looking at the relay is the headlight relay upgrade. You turn on the headlight switch and the relay triggers and sends a full 12volts to the headlights. The headlight switch sees the 12 volts but NOT all of the current that the lights draw. It is just a basic 12v circuit from the headlight switch telling the relay to turn on the headlights. The relay sees all of the current but the switch doesn't.
I sure suck at explaining things
clint

 

A relay is a device that controls a high power circuit with a low power circuit. As in Scoopers example, the headlight circuit is wired to the coil in the relay which draws very little current, probably less than a thousand of 1 amp, and it energizes to turn on the fog lights which probably draws in excess of 10 amps.

Questions are a good thing.

 

Guess I didnt type fast enough.

 

thanks for asking that question. . . that was a great explanation.

 

A relay is a solenoid.
I think of the word "relay" as a verb, (doing something)
the word Solenoid as a noun. (a person place or in this case, a THING)

Think about what your starter solnoid does....it "relays" the pos current from the battery to the starter motor(by way of a small current closing the internal contacts, connecting the two big cables, to start..)

I wondered about the difference for years....they're the same.

Just another way of thinkin' 'bout it....all the above are great explanations...

 

I have a full deck up my sleeve.

 

And I'm not done asking questions.

 

Thank you all so much for your explanations!! I get the full picture now. I was almost to the point of comprehension. Thanks for the push.

 

We'll send ya a bill.

 

Very good question and answers. I was wondering the same thing as I begin the installation of my electric radiator fan.

Thanks to all. Send the bill to Sooo.

Rick

 

I already paid attention.....

 

flux capacitor
dang it I was hoping I would be first