PC resets when its USB port is connected to a portable device on charger
PC resets when its USB port is connected to a portable device on charger
(OP)
Hi,
My company makes a portable device (battery operated). If we connect the device's USB port to a PC while it sits on the charger, sometimes device resets, sometimes the PC reset, sometimes both reset.
I think the problem is caused by the voltage differential between the grounds of the two systems. As the charger is powered by a linear, 2-prong AC/DC adapter (transformer-based), its "ground" is actually floating with respect to the PC's USB ground. I got hundred of volts between the two grounds of the two systems! I think when the two system connects through USB, the voltage difference causes a large current transient, which causes the two systems to reset.
Is there a way around this?
James
My company makes a portable device (battery operated). If we connect the device's USB port to a PC while it sits on the charger, sometimes device resets, sometimes the PC reset, sometimes both reset.
I think the problem is caused by the voltage differential between the grounds of the two systems. As the charger is powered by a linear, 2-prong AC/DC adapter (transformer-based), its "ground" is actually floating with respect to the PC's USB ground. I got hundred of volts between the two grounds of the two systems! I think when the two system connects through USB, the voltage difference causes a large current transient, which causes the two systems to reset.
Is there a way around this?
James





RE: PC resets when its USB port is connected to a portable device on charger
RE: PC resets when its USB port is connected to a portable device on charger
OP: This is something you have to sort out on your bench. There should definitely not be a large transient when you connect the device with charger to the PC. Does the charger have a UL or CE mark on it? Or been aproved by some other authority? What part of the world are you?
If you read hundred of volts wuth a DMM, then it may be capacitively coupled and nothing to worry about. If you can light a lamp with the voltage difference - then anything can happen. Including killing people.
Back to the drawing board, I would say.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: PC resets when its USB port is connected to a portable device on charger
I think that the problem is probably with the AC Adapter. If the charger is powered by a DC input from an adapter, then the charger is probably innocent.
RE: PC resets when its USB port is connected to a portable device on charger
A little related..... I have been playing around with a UNO and they can make a really cheap data logger. Unfortunantly, these reset and loose all the collected data when you pluga the USB port into a computer to read. The troubleshooting page on the web site says this now happens with newer operating systems. I have yet to try it with an old WIN98 system. Haven't reasearched it much but I gather that the new software now sends out a reset signal when plugged in to make it more compatable with later USB devices. You may also have a software issue in addition to an electrical problem.
RE: PC resets when its USB port is connected to a portable device on charger
Neither system resets when I earth grounded the charger's ground, but I don't think it's practical or safe.
James
RE: PC resets when its USB port is connected to a portable device on charger
I have also discovered the Uno. There, you've got bang for the buck. Love it.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: PC resets when its USB port is connected to a portable device on charger
> Actually, it is the exact opposite, i.e., it's SAFER. This is why most high-power devices use a grounding plug. By grounding the charger's ground, you guarantee that the two grounds are at the same potential.
> This tells you that your charger is badly wired. It likely has a direct connection between the AC input and the ground of the of the USB connector, and the AC plug is not polarized or not correctly wired for a polarized plug.
TTFN
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RE: PC resets when its USB port is connected to a portable device on charger
James
RE: PC resets when its USB port is connected to a portable device on charger
TTFN
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RE: PC resets when its USB port is connected to a portable device on charger