USB Voltage and Current Tester!! (version 1)





Introduction: USB Voltage and Current Tester!! (version 1)

About: Ex-Navy Gunner Learned to repair I.T. equipment because nobody local knew what the hell they were doing!


Since it's sometimes necessary to check your USB ports for voltage or if you are curious on what kind of Current draw your devices might be pulling, it would be great to have something to check these.

Now you can.

Instead of just hacking apart USB cables and checking these readings with a Multimeter or one of the Pen Drive style voltage checkers, this instructable will give you a tool that is painless to use.

Moving onward.....


Step 1: Parts!

The pics for this step did NOT turn out.
What you need:

Soldering Iron & solder (duh)
Epoxy, aquarium sealant or hit glue (optional)
1 PC Bay Cover any size will do
3 finishing nails or similar items to make into "posts"
1 USB Extender cable, or pieces from other projects ;)
1 Binder or Bankers Clip shown below. (unpainted)

It might not be a bad idea to coat the handles of the clip with a rubber coating, something along the lines of PLASTIDIP.

Step 2: Assemble+TEST

Drill 3 holes into the Bay Cover.

Two on one side about 1/2 inch apart

One on the far side of the Bay Cover, across from the other two, preferably between them.

We are only using the RED (5v) and the BLACK (GND) wires for this.

Cut the BLACK wire and strip a length of it on both sides of your cut (just enough to solder).

Cut the RED wire and do the same.

Now, place the finishing nails (or whatever you are using) through the holes from the bottom of the Bay Cover.

Solder both ends of the BLACK wire to the solitary nail.

Solder each of the RED wires to ONE of the nails.


Step 3: Glue That Puppy!

Just in the case the wires get pulled or the nails come out, let's fill the "body" of the Bay Cover with with glue of your choice.

That bugger isn't going anywhere now!

Step 4: Almost Done!

Now that it's mostly together, it looks kinda boring...

Let's work on that!

Step 5: Looks

I added a piece of RED electrical tape to the side that has the pins for VOLTAGE. (just in case I am not the one using the unit)

And a label, I also hot glued a piece of BLUE foam to the bottom.

Step 6: Usage-Voltage

Ok, now that it's put together, here is the info on how to use it!

To check VOLTAGE, use the binder clip ACROSS the TWO pins that you attached the RED wires to (see why I put RED tape on them?)

Then place one of your MULTIMETER clips/hooks/whatever on one of the RED pins and on the BLACK pin.

In case you didn't know, make sure your testing leads are in the correct ports.

Step 7: Usage-Current

Set your MULTIMETER ports, and attach your leads to the TWO pins, doesn't matter what color goes to which one.

BTW, it doesn't matter if the USB devices are plugged in at any of these stages or not.

Have fun testing your PORTS and DEVICES!!!!



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    21 Discussions

    I have Acer i5 laptop and all of my usb port are dead because of brownout I think the problem is in the board but when I plug a optical mouse the red light alive but no response in system my brother said the mother board of my laptop have damage like the resistors somthing like that, how can i fix the low voltage output in my laptop please help me I can't work because of this problem.

    Just make sure not to fill it with conductive glue!

    USB voltage and current test is truely not easy.Here is a perfect solution:
    The product will be laucned in June.
    You can buy it very easily on EBAY.
    Good luck!!!

    do you know how much current a ipod touch or iphone draws

    Actually you would need something plugged into it to test the amperage draw. And just a thought, it might be pretty easy to get a small switch to replace the bankers clip. You could also cut the lip of a bay cover and glue that to the back just for a better aesthetic appeal. Over all I would have to say this is a pretty great idea and I'm definitely going to build something simular. Thanks for the Instuctable.

    1 reply

    Already got a switch integrated.... It's small now. About the size of a small to medium FLASH DRIVE. I'll try to get it all up on the site this weekend, or at the latest MONDAY morning.

    If I get the time, it should be up sometime on FRIDAY! You WILL love it..... Just gotta figure out a few things.

    OK, got it all figured out, just assembling and painting today. I "should" be able to post it today.

    This is pretty cool. My take is that you can get Digital Multi-Meters from Harbor Freight for $3 apiece, so you could have a meter with built in USB lead from Dollar Tree. Project Cost: $4. :) (or you could splurge on dual DMMs and pay $7 to get voltage and current measurements) Awesome.

    1 reply

    nubie, Thnx.. I have been thinking your suggestion over, and I have a few more ideas that make the product smaller and still keep it simple. I'll make them and post when I get some more USB connectors in..

    I like this, now if I could add in a lcd and mode selector, to view voltage and other such info, that would be even cooler, of course so would a million dollars.

    1 reply

    I think this is a good idea, but some potential for shorting your USB port exists. Perhaps you could recess the test points and use a SPDT switch to break the line for the current measurement. I don't think it would be all that much more difficult to build, and would be more compact. For example, a scrap of pcb could be glued inside the housing, with holes drilled for access...or for a more robust device, a simple pcb could be etched with three pads for test purposes and solder pads for the switch.

    1 reply

    Thought about that, but with parts on hand, I came up with this current build. Plus, I wanted something I could clip on to, not have to hold probes against solder points, I tried that with an older revision, didn't like it. I thought about making something the size of a standard flash drive. I'm looking for parts as we speak.

    Suggestion: Step 2a-Test to make sure all connections are good. Now's the time to fix a bad connection, not AFTER it's been epoxied to death.

    3 replies

    Good point, I'll make a common sense note to it! My 1st revision, had a bad connection that I didn't find until I used a whole tube of epoxy on it.

    Second suggestion- instead of epoxy, melt a wax candle into the space. You can remelt it to remove it (might not be pretty, but it can be done) and I'm pretty sure it's cheaper than a whole tube of epoxy. Smells better, too. It's not quite as strong, but if it's only meant to stop short circuits or connections working loose it will do fine.

    That's why I also mentioned using Aquarium Sealant or Hot-Glue, just in case future modification was wanted/needed. But, since if I wanted to change, I'd just make a new version anyway, I went with the permanent option. :)