Getting a 5V supply from the board?

Hi,

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?

Thanks

Hi,
there should 5V exactly where you expect them between the sockets labeled 5V and GND on the “Power” section.
That’s the theory at least. So you either doing something wrong while measuring (wires to your meter don’t have good contact inside the socket on the arduino maybe) or there is a hardware problem.

If you got steady hands maybe you could try to measure the voltage between the pins from the backside. But be careful not to short-circuit the power supply when trying.

Eberhard

Thanks for the confirmation Eberhard. I went back and rechecked the voltages one more time, and then checked a known voltage (an AA battery) and found I was getting the wrong reading off my voltmeter. Then I realised I had the wrong setting - it’s actually a multimeter and I had it set to measure DC Amps!!! With the multimeter set to measure DC Volts, I am now seeing 4.9V or thereabouts… Doh!

Well, I did say I’ve only just started this stuff…sorry about the unnecessary question!

Hi,

Well, I did say I’ve only just started this stuff…sorry about the unnecessary question!

things like that happend to me a lot of times. Doing correct measurings is one of the hardest things in electronics. Whenever I get a strange reading on my meter I examine my measuring setup first. Usually that solves about 80% of the problems already :wink:

Eberhard

Yep, or trying to meassure Amps or m Amps with a meter with a blown fuse as i did recently.

Took me quite a while to figure out why my meter was not showing any current in spite of the fact that 3 ultra bright LED’s was shining happily :slight_smile:

Took me quite a while to figure out why my meter was not showing any current in spite of the fact that 3 ultra bright LED’s was shining happily :slight_smile:

Hmm, every multi-meter I’ve blown the current measurement fuse in (many now have PTCs) has cut current to the circuit too; this is usually my first indication the fuse is blown. Some of the nicer bench meters have LEDs indicating a blown fuse.