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?
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: