How do I test barrel plug polarity on USB Adaptors?

[Sinphaltimus]

I purchased 2 x 5v 3000mA USB Adaptors and a USB to 5.5 mm/2.1 mm 5 Volt DC Barrel Jack Power Cables.

 

EDIT: the power supplies from one vendor and cables from a different one. Both from China.

 

One set for my nanoPEB and one set for my 32k Side Cart. The barrel fits perfectly.

However; the USB to Barrel Jack does not make note of the polarity anywhere. So I'm reluctant to use it.

I have a pocket multimeter. Can I use this to verify polarity?

 

If yes, how? It's a generic HDM350.

Edited December 14, 2016 by Sinphaltimus

[+save2600]

You most certainly can use your DMM to figure out polarity. Stick the red lead in the barrel and black lead on the outer edge. If you see negative voltage indicated by a minus sign (-) just to the left of your reading, your center tip/inside of barrel is negative. No minus sign indicates positive of course.

[SIO2]

As Save2600 said, but I would add to set your meter to a DC voltage range nearest but greater than 5v before trying the test.

[+Lee Stewart]

And... You might check a battery with known polarity to insure your leads are hooked up properly.

 

...lee

[+arcadeshopper]

put your red lead where you want + to be, and the black where you want - to be.. turn to dc volts, test with power on if you get a negative number, its the wrong polarity swap leads and it'll become non-negative

 

Greg

[+jedimatt42]

BTW, you/we want tip-positive, so inside of the barrel should be about +5V. This is most common.

 

You can also do continuity testing with info from a page like this: https://www.moddiy.com/pages/USB-2.0-%7B47%7D-3.0-%7B47%7D-3.1-Connectors-%26-Pinouts.html

In this case, you want continuity between VCC and the inside of the barrel, and continuity between GND and the outside of the barrel.

 

-M@

[Sinphaltimus]

Alrighty then. Thanks all. Rolling outta bed soon, will check in a bit.

[Sinphaltimus]

OK, Looks good to me except, well, should I be worried about the overage?

Edited December 14, 2016 by Sinphaltimus

[+jedimatt42]

That should be ok for the sidecar 32k. Everything on that board will tolerate it.

 

I can't speak for the nanopeb.

 

-M@

[Tursi]

5.2v is within spec for a 5v adapter... also the voltage will usually drop slightly when a load is applied. You'll be fine.

[Sinphaltimus]

Sweet. Can't wait to get home. Looked up at the clock and I swear it slowed down right before my eyes.

[Sinphaltimus]

Works with 32k Side Port Expansion by M@.. Have yet to try the nanoPeb. I kinda don't even want to plug it in until I understand how to use it. I have yet to make time to RTFM.

[Shift838]

i use one with my NanoPEB with no issues. If you are supplying external power to the nano, then power the nano up first otherwise the TI will not boot.