![]() ![]() The screen is usually left connected at the transmit end and disconnected at the receive end so that may be worth a try. That approach is common in audio and industrial sensor signals for the reasons you've identified. I'm also not super keen to "experiment"if I might damage something, and also re-soldering the vga cables is fiddly work. ![]() I don't want to degrade my image quality, or risk damage. Is it possible to disconnect the ground signals inside the VGA cable to eliminate the ground loop without making it unsafe/losing the picture entirely? (pins 5-8, pin 10?) What would be the consequences of doing so? but does seem to indicate that the ground loop is the cause of the horizontal flicker/bars. I disconnected the safety ground inside the projector plug and the horizontal bars on the image went away, but I believe this is not a long term safe option. I've tried hooking them to the same power socket which didn't eliminate the horizontal bars on the projector image. ![]() I'm trying to eliminate ground loop between PC and projector via a VGA cable. Because they use transformers, the usual caveats about transformers still apply.Our hall has a projector hooked up to a PC via a VGA cable but we're seeing horizontal bars on the projector image when we turn on the lights in the hall. It's just a line-level transformer for each channel, packaged into something that's nice to use. That's also the idea behind a plug-in ground loop isolator. The ones that I linked to are at the expensive end that, from experience, sound just like the plain wires that they replace across the entire audio range, except for the ground loop noise of course. You can get them cheaper, but the cheap ones add distortion artifacts, especially at lower frequencies as the core saturates easily. Be warned though, that good ones of those tend to be expensive, like the ones that I mentioned here. Beware though, that this is VERY fertile ground for counterfeiters and other dodgy operations, so stick to the more reputable suppliers for this!Īlternatively, you could break the audio signal with some line-level transformers. Just take that power from a dedicated wall-wart and use its safety-required mains-isolation to also provide your ground isolation. If you're only using the USB for power, then that doesn't really help you because it requires a separate supply anyway for the circuit side. (and a separate supply for each side of course) They're stupidly expensive to buy as a completed module with all the relevant connectors and a case, but the chip itself is reasonable and only requires a handful of passives. ![]() Here's what Mouser has, and I'm sure everyone else has them too. If you're using the USB for data, then I think the cheapest way to do it is to put a USB isolator just behind your USB connector. It's not as effective as isolating the supply voltage, though, and you'll need an in-amp with good CMRR. I've done this in the past with an amplifier that I powered from the 12V supply of my computer. If a DC/DC converter that can handle your entire amp's power is too expensive, you can alternatively place a resistor (1k or so, plus maybe an inductor / bead) in the ground line of the audio connection and use an instrumentation amplifier to recover the difference signal between the audio ground connection (at the other side of the resistor) and the audio signal lines. Depending on the power requirements, this might be a little expensive, however. Your entire circuit is powered from an isolated source then and there can't be any ground loops anymore. Given that your circuit doesn't communicate with the laptop via USB, there's no need for a digital isolator: Just place an isolated 5V DC/DC converter in the 5V power path right after the USB connector. Simulate this circuit – Schematic created using CircuitLab How is this normally done? I'm looking for a simple solution without overflowing the board with too many new components. I have used optocoupler and dc-dc isolators before, but I'm not sure how I should connect them in this context. My question is, how can I implement a ground loop isolator for this application? I understand that a switch for lifting the ground on one side could be enough, but I want to find a solution that doesn't need a manual switch. The ferrite beads I use to separate digital devices from analogue (one side of the board is all analogue, the other digital, the ferrites go in between). The schematics below show how I'm powering the circuit. Otherwise, it works fine (like when transmitting audio from a phone and powering it from a power bank). When receiving USB power and receiving audio from a laptop, there is a ground loop. I'm working on an audio interface that utilises a microcontroller and a CS42448 audio codec. ![]()
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