How do I use a relay?

I have never used a relay before, and I don't know a lot about them. I think I might need one but i'm not sure exactly how it works. From what i understand, when electricity is passed through one set of pins, another set of puns allows a charge to be passed through, like an electricity powered switch. I might be completely wrong, and if anyone could help that would be great.

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lemonie4 years ago
I think I might need one

For what / why?

tim127 (author)  lemonie4 years ago
Me and my friend are working on a project and were thinking of different ways to do the circuitry and a relay seems to be the easiest.
lemonie tim1274 years ago
What do you intend to switch?
Solid-state semiconductors might be better.

tim127 (author)  lemonie4 years ago
I am planning to have an Arduino power the relay to turn on a 120v motor.
AndyGadget4 years ago
You're right - A relay is an electrically operated switch.  It can be operated from a manual switch, another relay or electronic circuitry.

I started typing a reply but it was getting rather long and involved so I think the best thing is to refer you HERE where there's a pretty good description of how relays work.  ('commom' is a typo of 'common).
Very neat pointer.
iceng4 years ago
It is important to understand the current carry capacity is is much greater then the switching current of the relay or any mech switch contacts...

tim127 (author)  iceng4 years ago
Thanks for the help.
Re-design4 years ago
You are right. the pins that power the relay connect to the coil. The switch contacts have a rating as to the max. power they can switch. If you go over the rating you will burn out the contacts.
tim127 (author)  Re-design4 years ago
Thank you!