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🤪 Help with Crappy USB Isolator

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Lord of nothing:
Hi
I got this: https://www.delock.de/produkte/S_62982/merkmale.html
The claim to be perfect for better measurement Results and so on...  :-DD
Now I opened up:



Well the Case is just made out of Plastic with no shielding.  :box:
What kind of component are the Blue Flat thinks? And what is there purpose?
The Problem is there is power from the Laptop to the USB Device.
Are the Black "Box" the Power Transfert?
Sadly the Noise level are still the same so the idea is to desolder the think who transfer the power and use the Powerjack.

wraper:

--- Quote from: Lord of nothing on June 26, 2019, 09:18:22 pm ---What kind of component are the Blue Flat thinks? And what is there purpose?

--- End quote ---
Those are ceramic capacitors.

--- Quote ---The Problem is there is power from the Laptop to the USB Device.
--- End quote ---
This is not a problem but how USB works. It seems this device can both supply power from computer or optional external PSU if higher current is required.

--- Quote ---Are the Black "Box" the Power Transfert?
--- End quote ---
This is isolated DC/DC converter.

--- Quote ---Sadly the Noise level are still the same so the idea is to desolder the think who transfer the power and use the Powerjack.
--- End quote ---
Is this noise level even related to USB? And what is the device to begin with? If it's cheap oscilloscope, you are unlikely to see any difference.

Gyro:
An interesting implementation.  :-\

The "blue flat things" are a pair of Y caps, they appear to be in parallel, connecting the two USB grounds [EDIT: or at least shields] together. Unfortunately they will also couple high frequency ground noise.

Yes, the black box is an isolated DC-DC converter. Unfortunately, if you bypass it and use the DC jack (9-30V) it will still be using the on-board SMPS (U4) to power the isolates side. Noise level will depend on quality of design.

The 480Mbps claim is suspect. It looks as if they are using an ADUM4160 with the number ground off. If so, it is capable of USB2 Full speed (as they say in the description) but that is 12Mbps. It's USB2 High Speed is 480Mbps. I am not aware of any single chip USB High speed solutions at the moment.

wraper:

--- Quote from: Gyro on June 26, 2019, 09:43:43 pm ---The "blue flat things" are a pair of Y caps, they appear to be in parallel, connecting the two USB grounds together. Unfortunately they will also couple high frequency ground noise.

--- End quote ---
Those are just usual 3kV rated capacitors, not Y safety capacitors. They might couple noise from computer but they also reduce noise from DC/DC converter. It does not seem they are connected in parallel. One of them is certainly coupling ground but other is not.

Gyro:

--- Quote from: wraper on June 26, 2019, 09:48:11 pm ---
--- Quote from: Gyro on June 26, 2019, 09:43:43 pm ---The "blue flat things" are a pair of Y caps, they appear to be in parallel, connecting the two USB grounds together. Unfortunately they will also couple high frequency ground noise.

--- End quote ---
Those are just usual 3kV rated capacitors, not Y safety capacitors. They might couple noise from computer but they also reduce noise from DC/DC converter. It does not seem they are connected in parallel. One of them is certainly coupling ground but other is not.

--- End quote ---

Sure, I meant Y caps in the context of cheap high voltage isolation caps - Y caps are used in high volume, so cheap.

EDIT: I can see the marking on one of the caps now, yes, 3kV Z5U, no agency markings - I need to get my eyesight checked!  ::)


--- Quote ---It does not seem they are connected in parallel. One of them is certainly coupling ground but other is not.
--- End quote ---

Well spotted, I missed the isolated pads, possibly one coupling the 5V rails as well then.

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