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Normally open and normally closed 5V relay pins

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(@yurkshirelad)
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Quick question. Are the normally open and normally closed pins on a 5V relay (like the one in the picture) standard? Are they usually the same pins or might they be reversed from different manufacturers?

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codecage
(@codecage)
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I haven't used enough brands to answer your question, but I would suggest you take a look at the datasheet for the part you have, or maybe try an Ohmmeter on the pins to see if you can determine the pinouts.  Two pins should be the windings of the relay coil. Then one of the pins should be the common contact on the SPDT switch.  With the relay on the bench that common will be in the normally closed position so you will have a short between the common and the NC (Normally Closed) pin.  Now put 5V to the coils (if the relay is a 5V relay) and now you should be able to see which two pins are now shorted.  Whichever pin is one of the pins used in the NC position, then you have identified the "common" pin.  And you also now know the NC and NO (normally open) pins.

Good luck!

SteveG


   
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(@yurkshirelad)
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Thanks! I'm not sure I'll tackle it quite yet, as I probably have the potential to do some real damage! I first need to make sure my Arduino Uni can safely supply enough current or whether I need to use something else, I think I read somewhere the Uno can drive a transistor, which will drive the relay. More reading!

It's a Songle 5V Relay SRD-05VDC-SL-C. I managed to work it out with my multimeter in resistance mode. I found this pin diagram online, which matches the Songle:

?resize=281%2C250

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(@yurkshirelad)
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Though I did get an example circuit working in circuitjs. Cool!

circuit 20210204 1958

   
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(@yurkshirelad)
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Joined: 3 years ago
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Success! I built two simple circuits with a relay and it worked. Nothing blew up! Bonus! 😀 


   
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