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Topic: Relay help (Read 1 time) previous topic - next topic



I've been pretty good with Arduino projects up till just about now. I need to throw an already powered 12v switch (There's a switch there I wanna replace with an Arduino control). I (think) that a relay can help me use my Arduino 5v to control a relay that powers this, problem is I don't know what relay to look for nor how to wire it!

Any help is appreciated!



Any help is appreciated!


Really - is it that difficult to figure out? Now, of course, that'll get you the "how", but the what is slightly more complicated: You basically need to know some specifics about what kind of load you are switching. You say it's a "12 volt" switch; so does that mean the load is really 12 volts? If so, then what kind of current are you looking at? If you don't know the current, then anything about watts? At any rate, once you have a figure, then you need to figure out the current, so you know what kind of contact rating you need for the relay. If we are talking about an automobile circuit, though, then a simple SPST Bosch relay rated at 40 amps or so, while it might be overkill, is fairly dead standard, and can be found at a junk yard.
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.


In addition to the current rating of the relay, if you're going to power it directly from an arduino pin then just make sure you find a relay with a very low-current coil so you don't let any smoke out of the arduino.  There's plenty of them out there, I have some Omron relays that only draw 25 milliamps for instance.
solar robotic mobilist


Elsewise you'll need some transistor action to power the relay coil.
solar robotic mobilist


Thanks! I really appreciate the help; I still can't seem to get it to work; Let me explain -

I have an existing device with a 12v switch in the wall; I need a relay the flip that switch ( I assume I need a relay )

Here is a lame-o diagram of my situation. Should I get some readings of the current to be able to know which relay to look for?


I have an existing device with a 12v switch in the wall

If we knew what that 'device' is, we may have some idea of the current it draws. :~
Are you intending to replace the switch with a relay or do you want the switch to remain in place and be operated by a relay (in that case, a solenoid would be a better option.)? There is also a third option where either the switch or the relay will switch the 'device' on (switch and relay in parallel).


HI, Take a look at Arduino Power info here: http://arduino-info.wikispaces.com/ArduinoPower

Relay boards like these can be easily driven by an Arduino, pin:  http://goo.gl/jJRYM

DISCLAIMER: Mentioned stuff from my own shop...
Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
HOW-TO: http://ArduinoInfo.Info

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