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
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:
Thanks
Though I did get an example circuit working in circuitjs. Cool!
Success! I built two simple circuits with a relay and it worked. Nothing blew up! Bonus! 😀