0

Problem with USB Isolator as USB CRO Protection
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

Problem with USB Isolator as USB CRO Protection

by netless on Thu Jun 06, 2019 9:01 am

I have just purchased a USB current meter & USB isolator from Adafruit.

I bought the USB isolator to isolate my USB CRO after watching the promotional video on typical uses for the Adafruit USB isolator including USB CRO protection.

Both items have recently arrived - the USB current meter works fine.

However the USB current meter shows that my USB CRO is pulling a minimum of 400 mA [2W] and even a bare feather Huzzah with a simple I2C HTU21DF Temperature & Humidity sensor is pulling 70 mA.

My question - with a 100 mA power rating is this Adafruit USB isolator fit for purpose for protection of a USB CRO?

Should I be looking at some other from of common ground protection for my USB CRO

Apologies if I don't seem too positive here, all of my previous experience with Adafruit products has been excellent, however this device does not appear to be capable of isolating my INSTRUSTAR USB CRO, which was the intention of my purchase.

netless
 
Posts: 9
Joined: Sat Sep 22, 2018 4:20 am

Re: Problem with USB Isolator as USB CRO Protection

by adafruit2 on Thu Jun 06, 2019 7:29 pm

it really depends on the USB device - you will need to measure the 5V draw on the device side to aim for 100mA output. Small devices work great. if its more than 100mA draw, you cant use it.

adafruit2
Site Admin
 
Posts: 18395
Joined: Fri Mar 11, 2005 7:36 pm

Re: Problem with USB Isolator as USB CRO Protection

by netless on Thu Jun 06, 2019 7:42 pm

OK - So it is clear that the 400 mA draw of my CRO is far two high for this device.

Would it be possible to use the isolator upstream of a powered USB Hub, which in turn supplies power to my CRO.

I'm assuming this may solve the CRO power draw on the isolator, while still allowing data throughput.

The USB hub has no common ground, so this should keep the isolation intact.

Is this likely to work, or do you see that there may be some power / data conflict between the isolator and the hub?

netless
 
Posts: 9
Joined: Sat Sep 22, 2018 4:20 am

Please be positive and constructive with your questions and comments.


cron