How to safely test USB connector installation

again.

to

Well, if you download the USB spec from

you can see which contacts carry the 5V. So you can measure with a DVM whether these contacts carry 5V in the right polarity. You can then safely plug in a device to see if the polarity of the datalines was ok or not.

Meindert

again.

to

I'd make a test cable. Cut up a USB cable and add some resistors and LEDs between vcc and ground. Have a GREEN led light up for a good connection and RED for bad. Then plug it into your SBC and check for a green light before you connect any USB devices.

You can work out which pins to use on here

Peter

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Sure -- but without experience with that bus, I wasn't sure that this would be a "perfect" test. If you're right -- and the next poster has a really nice suggestion of making a test cable with LEDs (and resistors, of course), it'll be trivial to check every board from here on out.

Thanks Norm

You also could buy a cable tester. This will normally test RJ-45, RJ-11 (phone jack) and USB. Today they are relatively cheap.

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LEDs

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before

I've seen RJ-45, RJ-11, and coax testers but never noticed a USB one. I'll have to check my preferred supplier's catalog again.

Thanks much for the suggestion.

Norm

Mine is called Skymaster Remote Cable Tester DCJ-0102 (made in Taiwan), testing RJ-45, RJ-11, USB and BNC (coax).

Link to the new version of this tool:

Trygve

Kensington sell a USB-powered LED-on-a-stick which would seem to do the job.

job.

That won't do the job. You'll probably wreck it with reverse polarity and because it has charge storage you'd have to wait an hour for the LED to go out after you disconnected it.

Peter

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a

resistors,

Actually, my wife has one just like that. Thanks for the warning.

Norm

"moocowmoo" wrote

That's interesting. I didn't think that these were anything more than an LED and a resistor. What else do they have in them?

LED

I reckon he's confused by the statement 'Uses less than 90 seconds of battery charge per hour'

ie the power used by the LED in an hour is equivalent to running the laptop for about 90 seconds. I looks to me like it's just an LED and a resistor in some snazzy packaging. Anyone actually taken one of these things to bits?

Richard

I found at

an inexpensive USB tester -- it's currently selling for $5! and it's already saved me because as soon as I got it I plugged it into a known good computer's port and then into the CPU board and it showed that one is wired correctly and one isn't! That's an incredible return o nmy investment since it would have taken me at least 5-10 minutes to hack up a cable and connect a meter.

Norm