USB Isolator for student lab // microcontrollers - Page 1
Forum section: electronics / general

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: October 16, 2017, 02:14:14 pm
content: Dear forum,how much should I spend on an USB Isolator / what devices can you recommend?We are building a physical computing lab for our students and an isolator will be needed to protect the students laptops from their "creations" while programming. It will be mostly flashing Arduino firmware and maybe use with Salea logic analyzers, but who knows what comes along the way.I have been looking at several different devices from 35€ up to 280€, but can not really make up my mind.The most appealing candidates are: CESYS Care01 and DELOCK 62487 - both around 80€.I like having separate cables instead of the "dongle style" and prefer spending a bit more on robust equipment. However, there will only be extra low voltage circuits on the "student build" side.Are there any recommendations?Thank you,Frederik

author: wraper
author_rank: Unknown
timestamp: October 16, 2017, 02:18:50 pm
content: Quote from: frozenfrogz on October 16, 2017, 02:14:14 pmBoth are full speed only (12 mbps).

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: October 16, 2017, 02:27:13 pm
content: Hello wraper,thanks for your quick reply.I know about the speed issue, for firmware flashing this should be OK, but of course you can not do a lot else with legacy USB.So would you recommend spending more like 250€ per device and get something like the ALLDAQ ADQ-USB 3.0-ISO instead?Since I have never really used such devices I am open to all your ideas

author: Jeroen3
author_rank: Super Contributor
timestamp: October 16, 2017, 02:33:43 pm
content: Major drawback of all those isolators is the limited bus supply of 100mA, except an external supply is connected.We bought a dozen a few years ago, but those little recom or tracopower dc-dc things kept failing. External supply is required I'm afraid. Especially if the arduino will be bus powered.You could also get a few robust USB Hubs from BB-Elec, like theUHR304.Though not isolated from mains earth, which does not look like to be a requirement, it can provide isolation protection for the host. As well as TVS diodes on supply and data, with overload switches.If you get the 204 it's without host isolation, it should be USB 2.0 instead of 1.1.Which is a must forstreaming logic analyzers!

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: October 16, 2017, 03:03:22 pm
content: Merci infiniment Jeroen,you are bringing up good points and I should do some more investigationThe B&B Electronics devices look like an interesting option.Could not find a lot of resellers, Digikey prices for the UHR304 is 300€ and the USB3.0 USH304 350€.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 16, 2017, 03:54:07 pm
content: I got mine from an eBay seller in Slovakia.

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: October 16, 2017, 03:57:11 pm
content: I'm aware it's also only "full speed" (aka 12Mbit/s) and not rocket science, but as least my own creation can deliver 400mA with a 2W DC/DC and provides some kind of regulation on the the output even for a DC/DC without regulation.http://lemmini.de/USB%20Isolator/USB%20Isolator.htmlI'm using two of these for months (*) now mainly for stuff like connecting cheap chinese USB/serial converters on prototyping boards where I fear I might short something at some time.Both are on almost all the time so I would consider them stable.* Just noticed that I did them in 2015. So it's more like two years now. Boy, time flies.