so i’ve had consistent issues with raspberry pi AV inputs shitting out and i’m all but positive its just feedback from bent or diy devices frying that part of the pi, so i’m thinking i’ll make some sort of input protection with an AD8072 or LM6172 - anyone have tips for that kind of arrangement? someone mentioned two inverting buffers would be the way to go but i have extremely low confidence dealing with op amps… this is the schematic i was going to try. I’m hoping to steal the power from the gpio pins on the pi
any and all advice is greatly appreciated - this is the schematic i ripped from the 6172 datasheet and crudely arranged
I expect the biggest possibility for damaging lower power chips (like the RPi) could be from voltages outside the supply rails. So you could use a circuit with a diode pointing to the highest voltage rail (+3.3V? +5V?) and away from the lowest voltage rail (0v/GND) to ensure out-of-range voltages are drained away. Something like this? I’m not exactly sure what value R1 should have, or what sort of termination might be required. Maybe a unity gain op-amp with 75 ohm input termination before the diodes, plus another op-amp afterwards with 75 ohm drive? I’m not really an expert at this, though, so more reading and googling is probably a good idea. It might also depend on exactly what the circuitry of the video input on the RPi looks like.
It might just be simpler to just run the output from the bent gear through some other more resilient device first, to protect the RPi.
You mentioned “inputs” a few times, but the RPi doesn’t have video inputs. Do you mean the video output? Or do you mean an external USB device that you’re using for video input to the RPi? If that’s it, then what’s the device?
Hey I imagine you sorted this out already, but there’s a good circuit for a video buffer using a LM6172 in the LZX Cadet Sync Generator schematic. Here’s the PDF of the schematic: lzxdocs/Cadet I Sync Generator Schematics.pdf at master · lzxindustries/lzxdocs · GitHub
And the buffer circuit (can just leave out the wire that goes off the image from what I understand):
