0
\$\begingroup\$

I'm making a retro-fit device (so I have plenty of parameters that aren't in my control) where we're adding USB connectivity to the device for use with a PC.

The device is battery powered, and the battery configuration varies greatly from one user to the next.

There is concern that some users are using a battery holder that has exposed rivots that may come in contact with our USB connector's shield, thus shorting the battery's + and - with the shield material.

I'm less concerned with what happens to the device if they do this than I am for thier safety and what may potentially happen to their PC if I connect the shield in the usual way (ie. 1M res / 4.7uF cap between shield and ground). If I understand, the host side will have the shielding go directly to ground.

I'd want to be either a) comfortable that a short wouldn't be as tragic as I'm imagining or b) make electronic changes to my circuit board such that said short would be protected against, even if damage to my circuitry occurs so long as the user and PC are protected.

Unfortunately, due to previously mentioned constraints, I can't physically ensure the battery's poles don't come in contact with the USB shield, and I'm not soliciting responses to that effect. Of course I can warn the user by way of instruction manual and/or included notice to be careful if they use that type of battery holder, but if there's something I can do electronically I would like to know what it might be.

Thanks.

Clear enough?  lol

\$\endgroup\$
  • 1
    \$\begingroup\$ Photos of the battery holder and your board as well as a sketch would really help us help you. \$\endgroup\$ – Dwayne Reid Jun 6 '15 at 1:19
  • \$\begingroup\$ Thanks. I'm not sure how that would help. Pictures would lead to "well they could do this" suggestions but I can't depend on the user doing or not doing something. The holder is out of my control and due to physical placement constraints, so are the physical properties of my board. So I guess I'm just asking - will the PC be damaged if a battery's pos/neg are shorted on the shielding of a USB cable? \$\endgroup\$ – bcsteeve Jun 6 '15 at 2:19
  • 1
    \$\begingroup\$ Well, if you mean that the same single shielding of a single USB cable is connected to both poles of your battery, then the PC will definitely not get damaged - but the USB cable shielding may. If the poles of the battery are connected to two wires in the USB cable (one each), or one of them gets connected to the shielding and the other pole gets connected to one of the wires - that could kill the USB port in the PC. \$\endgroup\$ – Laszlo Valko Jun 6 '15 at 2:24
  • \$\begingroup\$ No, the wires aren't in danger of coming into contact with anything other than what they are supposed to contact. I'm not an artist, but I've added a picture of what I mean as best as can. Clear enough? \$\endgroup\$ – bcsteeve Jun 6 '15 at 4:11
1
\$\begingroup\$

Cover your USB connector with a pre-cut piece of Kapton tape that glues down on the top and folds over the sides and back, like so:

enter image description here

The photo is from Sparkfun and this article describes the solution in more detail.

\$\endgroup\$
  • \$\begingroup\$ Thanks, really. But I was specifically trying to avoid suggestions regarding physical remedies. There's actually no need at all to place that tape on, because it comes pre-applied from the part manufacturer anyway... and looks just like one of those kinds of tapes you're supposed to peel off and I'd say some, if not most, users do. I know I would. I suppose I could invest in customized "do not remove" tape, but that's a cost of time and materials I'd rather avoid. If commenter Laszlo Valko is correct then I have my answer... non-issue. \$\endgroup\$ – bcsteeve Jun 6 '15 at 14:11
  • \$\begingroup\$ I've edited the question so it is more clear that I'm looking for an electrical answer, not a physical one. But gain, thank you for your effort. \$\endgroup\$ – bcsteeve Jun 6 '15 at 14:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.