Saturday, January 16, 2016

USB Power meter

I stumbled upon this small gadget at the local dollar shop (called Action) which was on sale for below 3 Euro. It looks like this:

So what is it. It is a usb power meter. It measures the voltage that your USB port supplies but more important it also measures how much Ampere is drawn from that port.

This is great for measuring the current a project draws.

First I attached it to mu computer's USB port:

Well it shows that my computer just supplies 4.87 volts.

Next step was to attach it to a power bank I have been using regularly for all kinds of projects.

So my power bank supplies a bit more as 5 volts. As there was nothing attached to it there was no current withdrawn.

Next step was to attach my electronic hour-glass. This starts with ten leds on. That must draw some current:

And yes it does. It draws 0.02 amps. Now that is not a lot. That is just 20 miliamps. Not bad for 10 glowing leds. If you wonder how this is possible check a technique called Charlieplexing. I am going to do a series about this.

Now lets look at my Larson Scanner:

Just 0.03 Amps. 2 leds are on. Again not bad and again due to the Charlieplexing technique.

As my powerbank has a capacity of 2 amps the Larson Scanner should work for about 60 hour !!!!

So this little device shows me how much current a project is using, and that tells me what capacity my power source needs to supply. 

Ah you might say: not all projects are powered over USB. That is true. However most prototypes are made by powering therm over USB and this will tell me the power it will draw.

As told I found this at my local Euro shop, but most Chinese verdors sell it also.

Till next time.
Have fun.
Luc Volders