Question about USB Isolation

[gasmanpopey]

Hi All,

Just looking for a bit of advice. I’m planning a little project to add a couple of temperature controlled fans to my home network rack as it’s getting a bit toasty inside after adding some new equipment.

I’ve been looking at PC case fans, and some of the fan controllers that are available. I’ve found a controller and a couple of fans that look like they fit my requirements, but the controller is designed to live in a standard PC case, so the USB connection (for management/programming) needs an internal USB header and the controller needs a SATA power connector.

Where it gets more complicated however, is that there is no ATX style PC in my network cab - I do however have a little MSI Cubi that I use for management of a few things, so I need to convert the USB cable from a header connection to a type ‘A’ and I need to find a SATA power brick. The USB connection is easy, and I’ve found a good little triple rail power brick for the SATA power so that should be okay too.

This leads us to my question – as the Cubi AND the fan controller are powered by separate switch mode, floating power supplies, do I need to isolate the USB cable to avoid cooking something?

I’ve been pondering this for a week now and not come up with an answer I’m confident enough in to chance cooking my Cubi, so was hoping someone might be able to tell me i'm either right or wrong. In my mind, the USB ground would tie the two 0Vs together and thus it would be fine. But then i'm not sure how USB ports are wired up. My thinking is its no different to having a USB hub connected to a laptop.

Would appreciate any insight you could offer.

Cheers,

James

[ConKbot]

Nope, no problems with both supplies being isolated. Its like plugging the SATA power adapter into a drive that gets hooked up to a USB adapter and plugged into a laptop, where both the laptop brick and SATA power brick use 2-prong plugs.