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Author Topic: Relay to close 120volt contact triggered by ground  (Read 390 times)
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Hi, can anyone help me figure out a way to turn on my porch light, that will be triggered by a ground. So when I ground, the light comes on, when I unground, it goes off.

Thanks!
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You want to use a relay.
Wire up the relay through a transistor to the arduino.
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Who or what will be doing the grounding?
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Its my ip cameras external outputs, i know not arduino related, but you guys are smart. Ill house the relay in the light, where ill also have a 12 volt connection if that helps
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In that case, it would help to know the specification of the IP camera output. As you are talking about "grounding", I presume it is an open-collector or open-drain output; but it may or may not be rated at +12V.
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It's an open-collector output, and it looks like it's designed to drive a relay already, without using an external transistor. So connect the coil of a 12V relay between the output and the +12V supply, and connect a flyback diode in parallel with the relay coil.

If you look on page 145 of the manual, it should tell you the current sink capacity of that output.
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