USB Reboot

[eman5oh]

I was checking some PLC firmware today and on one of the three T1H-DM1E cpu's rebooted the moment the usb cable touched the jack, I have seen this a few times in the past and was wondering what could cause it? I was using a laptop running on battery power if it makes any difference.

[BobO]

Really? Yuk.

There is always a greater potential (no pun intended) for ESD when the devices are floating with respect to one another. That said, this is the first I've heard about issues with the T1H, so I'm a bit surprised. We'll look into that.

I would be interested to see if it ever does it if you touch the metal part of the cable with your hand, and then touch the connector with your hand, before plugging in the cable.

[eman5oh]

Tried to get it to repeat at my desk on a test plc and no reboots tried with the laptop plugged in and on battery. I thought it could be static, as it only happened on the first plc and the next two I made sure to ground myself before touching anything. 

[Scot]

I've had that happen with an Allen Bradley MicroLogix PLC connected through a Serial-USB adapter and the AB serial cable while having the laptop connected at the same time to an AB touchscreen.
The USB connection arced when the outer, grounded, part of the connector touched the laptop and pulled down the 24v power supply in the enclosure.
Somehow one device had the outer shield connected to 24V-common and the other device had the outer shield connected to +24V.