Basically what the (unconventional) question says! I don't have a voltmeter at home. How can I fashion one, or use some kind of test to determine if current is flowing? I know it's a relatively low amount, so I'm not worried about hurting myself (I don't know how much current it will be), but I know that also may make it hard to tell. The device will likely be warm in general; it is powered by 5V. There will be other "outlets" on the device without voltage flowing that I can compare to. I don't care at all about the specific amount. I just want to verify whether it is or is not flowing (i.e. whether my code works), and I won't have access to the ideal tools over the weekend. Is this possible? Any ideas?

  • \$\begingroup\$ The simple answer is you cannot! you need a VOM and or a current meter to measure these parameters. What code are you talking about? It would be best to rewrite your question with more details and what you are working with? I do not know the resources you have or your skill set so I cannot tell you another way to make the measurements. \$\endgroup\$
    – Gil
    Jun 12, 2021 at 3:08
  • 2
    \$\begingroup\$ voltage does not flow ... current flows ... voltage just is \$\endgroup\$
    – jsotola
    Jun 12, 2021 at 3:10
  • \$\begingroup\$ your tongue may work ... put two AA cells in series ... put the two wires on your tongue ... you may be able to feel it ... i know from my childhood that a 9 V battery is easily felt \$\endgroup\$
    – jsotola
    Jun 12, 2021 at 3:15
  • \$\begingroup\$ If you gave more details about your circuit we might be able to come up with specific ideas. \$\endgroup\$
    – ErikR
    Jun 12, 2021 at 3:23
  • \$\begingroup\$ "whether my code works" - what is your code running on, and how will a voltage indication of 1-3V tell you that it 'works'? \$\endgroup\$ Jun 12, 2021 at 5:33

1 Answer 1


You could take a compass and place it over (or even near) one of your wires like in this blog post:


It will deflect when current runs through the wire.

Here's a video demonstration:


To enhance the deflection you can wrap the wire around the compass several times.

You can install a magnetometer app on a smartphone and use that in place of a compass.

If you don't have a compass or smartphone available, you can make a floating compass with a needle and a magnet:


Don't have a magnet? Just use some silk or wool:


  • \$\begingroup\$ super helpful! appreciate the huge range of household items. \$\endgroup\$
    – qmstatmech
    Jun 12, 2021 at 15:52

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