USB Question

[fifty60]

Would it introduce noise if a metal inclosure was able to make direct contact with the metal housing of male usb connector? A panel mount USB is constructed in such a way that the metal enclosure of the male USB could make contact with the stainless steel enclosure. Would this create any problems in the event that this contact happens? The pins inside of the male USB would not make this contact, just the housing around the pins.

 

[EV607797]

I don't see where there would be a problem. The shield of the cable is bonded to the metal shells of the connectors. This isn't a signal ground connection; it is a frame ground. The connectors on most equipment (printers, computers, etc.) have their shells connected to the grounded frame anyway, so unless there was a major fault causing the panel to become energized, it will be fine.

 

[AdrianWint]

Although I agree with everything said above .... my experiences in my 'day job' suggest that, in practice, things aren't so clear cut.

We often get problems with random crashing of computers, in particular laptops, when the 'screen' of the USB is allowed to make contact with frame ground on another piece of equipment. Since realising this & taking care to ensure that there is no contact between the frame of a USB connector & any surrounding metalwork we have seem a dramatic decrease in the number of USB related system crashes.

 

[SceneryDriver]

USB isn't really and "industrial" protocol. As such, it (or devices connected via USB) can be susceptible to common-mode noise induced on the shield, especially in industrial control panel environments. As said by others, many computers and USB devices don't cope gracefully with such noise and either crash, or become damaged. Isolate the shield in the panel, and don't let it touch a "grounded" backplane. I put grounded in "" since there can be high frequency noise on the ground plane when around things like high power switch-mode power supplies, VFD's, servo drives, etc...


SceneryDriver