I’ve just begun learning about Arduino and have been really impressed by how easy it was to get some simple circuits up and running. I’m driving my board via my laptop USB and all seems to be working just fine…except…I can’t seem to get a 5 volt reading off any of the +5v outputs on the board. In case I’m not making sense (and that’s probably the case!!) what I mean is that alongside the analog inputs 0-5 I can also see Reset, 3V3, 5V, Gnd and Vin. I thought that under normal operation, I should be able to see 5v across the Gnd and 5V pins, but when I measure this with my voltmeter, I get a variety of readings, mostly between 50 and 80 mV but occasionally -1V, i.e. polarity is switching.
I guess I’ve misunderstood what these pins do, and what they can be used for. Can someone please clarify this for me?