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Power ground isolator7/2/2023 the raspberry pi has not alot of current to offer on usb`s and B. it will include relais and other stuff and i normally like minimalistic approaches, specially in audio, so i think if i can stay as close to the very simple drawing i made the better I was thinking maybe the switching could be done with a microcontroller but im A. Yes completely mirroring what the Ifi idefender does is probably(pretty much surely) out of my (knowledge)-range but i try to search a solution that is "kinda" the same functionality but much cheaper (maybe i even do my first pcb design, im not sure yet), If you consider to DIY something like the idefender, I think you'd have the necessary knowledge to troubleshoot the earth/groundloop's and solve the issue groundup.Īll the ifi "fixer" products are really designed to be "plug'n'play" for people with very limited technical knowledge, so it has to be something that comes in a box and can be plugged in.Īnyone with the relevant technical knowledge can probably get equal or better results resolving the underlying issues or making something more optimised, that simply cannot be let loose with good conscience on unsuspecting and technically challenged customers. While they obviously work I feel that most are overkill and solving the underlying earth/groundloop's is free and works just as well. It is a sufficiently frequent problem in my experience, that I designed solution into several ifi USB products and it eventually got elevated as standalone product. breaking the loops through mains cable's and interconnects), it is. If you have problems caused by ground/earth loops involving the USB connection that cannot be solved in other ways (e.g. The "idefender" in effect automates this switch and selects external power if available. The switch shorts out the 100 Ohm in case it is not needed or causes problems. Noise problems with USB are almost 100% down to earth/groundloops and this breaks the part of the loop through the USB Cable is reduced by around 80dB. So this ONLY works if supplying new power to the downstream USB device. If there is no DC power current flowing in the USB lines, the 100 ohm resistor is normally ok to let standard USB devices complete a successful handshake. This sits between input and output ground, the switch bridges it out. There is a reason for it being a manual switch on the the original iUSB (Power).Įssentially being this switch is a earth/groundloop breaker, specifically a 100 Ohm resistor. I know normally we should use usb isolators, but im trying to find a cheap solution/workaround (specially in the case of high speed usb), for example to disconnect my attached SSD to the raspberry pi beside the data lines, since i think connecting V and GND also introduces noise back to the system Is this even a good idea? even if we get GND disconnected too, will noise be transfered over the data lines? or do most receiver chips reject noise on the data lines? Can i use a isolation transformer and just connect ground to the output (and leave V unconnected)? or will this not work? (if just connecting GND wont work, how about a large resistor between secondary V and GND and use the GND this way?) maybe current sensing on the output and disconnect ground after 1 sec? how can we leave ground connected but disconnect it as soon as the usb device is sucessfully connected? (since if gnd is completely disconnected most devices wont connect sucessfully) So in the end just D+ and D- should be connected from input to output, V and GND will come from external power input if possible disconnect GND too from input and use GND from external power disconnect V from input and just use external power 3 usb connectors, one input, one output, one external power I try to build something similar to the Ifi Idefender
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