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Topic: Power supply for relay (Read 739 times) previous topic - next topic


I have a project involving a relay, PIR sensor, and AC fan. All finally works as intended but it is so ugly, really ugly, with two wall warts, one supplying the Arduino, another for the relay, and a wire for the fan, all coming from a power strip. A single wire from the AC outlet to a box would be much more elegant.  I assume the Arduino and relay can't be supplied by a single wart via transistor, or in this case, a tip120?  Could mains power be accessed from a single terminal inside a project box by the two warts? Ignorant question, but anything coming from the wall gives me the Willies!


You have not said what voltages and currents you are using.

I can guess that your relay requires more than 5 V and/or more than 30 mA.  Perhaps you should look for a different relay.

If your relay used 5V and <30 mA you can run it directly from an Arduino pin without a separate power supply or transistor driver.  If it uses 5V and >30 mA (up to about 400 mA) you can drive it from the Arduino with a transistor.
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Thanks for the help. The datasheet says 40ma. Having ordered a bunch of these, guess I will try to use them. If run from a transistor, I assume two wall warts are necessary?


You have still not said what voltages you are using for the relay or Arduino.
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Sorry, I am using 6v for the Arduino Pro, and 5v for the 5v relay.

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