# Do any Arduino boards come with a USB isolator?

#### Twigg

Joined Jul 25, 2015
23
I'm looking for an Arduino or other programmer-free micro-controller board with isolated USB ground. I recently made a bonehead error in the lab where I used an Uno overnight to read off a signal channel I'd amplified by a factor of 250 and had a ground loop from the input ground to the USB plugged into my laptop. I came back in the morning and found the serial data had been going back and forth between 0 (probably was saturating negative) the amp supply rail (5V). That issue's been resolved, but I still want a solution for the next time I need to use an Arduino and don't want to risk damaging my computer because of an oversight. What I'd really like is an Arduino (or other programmer-free micro controller) with an ADuM4160 or equivalent device built-in out of the box. This kit is the closest thing I've found so far, but I'd rather not spend $33 on the isolator plus$25-35 on an Arduino to have them be two loose boards with a dedicated cable. Is there a board that puts 'em together? Would I be better off making it myself? Alternatives? Thanks!

#### shteii01

Joined Feb 19, 2010
4,667
Uno has "translator" chip that translates UART into USB. So you can "sort of" say that uC is isolated. You have ATmega328P to ATmega16U2 to PC. As you can see the uC is never directly connected to PC.

#### Twigg

Joined Jul 25, 2015
23
Uno has "translator" chip that translates UART into USB. So you can "sort of" say that uC is isolated. You have ATmega328P to ATmega16U2 to PC. As you can see the uC is never directly connected to PC.
Ok, that makes sense. Thanks.
Still that wouldn't isolate the grounds, would it? Based on that, the PC should be safe, and plus it looks like from the official site that they put some sort of fuse in too. I still don't like the idea of having the USB ground coming off a laptop and the ATMEGA ADC ground being tied together. Seems like it'd be really noisy and bad in this kind of scenario where I was looking for a signal at less than 10mV before amplification. I guess then it's the Arduino that's under stress from the excess voltage. Before removing the ground loop, I had a PuTTY session going showing that the analogRead was showing 1023 and 0 off and on and random times during the night. After removing the ground loop, it read a stable 500+/-10.