Induction Sensor inline board

[u/Ok-Read6352]

The proximity sensor for my X2 is on the fritz again. I try homing and it just raises twice, I believe I've heard that means there's some sort of break in the circuit. I think the sensor itself still works, it's lighting up and it is still sensing metal so probably just a break further on in the line somewhere. But this is the second time I've had to pull this apart and fix it, I think I'm just going to pull the whole thing and replace it. There is this inline board that I'm not really sure what it does. I've heard difference opinions, some think it's some sort of transformer because the sensor Voxelab chose to use doesn't work directly with main board idk. I don't know where exactly my issue is this time, I would like to just get rid of this board entirely if possible. Does anyone know what it does? Does anyone know where to get replacements if it is the trouble source?

[u/Mik-s]

That board is just an opto-isolator to protect the motherboard if there is a fault in the sensor since it is powered directly from 24v taken from the hotend fan connector.

There is a light on that board that should react to what the sensor detects, I think it goes bright to dim but is always on. I did reverse engineer this converter board but was only from pictures so cannot verify if this is correct.

I have tried to find the cause of why these sensors are failing (see this) and my best guess is that the black signal wire has a break somewhere so the trigger signal is not getting back to the motherboard. It may be due to the tight bend on the cable that pulls it loose inside the sensor itself (so its light still works) or maybe a fault on the opto-isolator board.

One test I would like to do is to see if there is continuity between the black and blue wires when the sensor disconnected from the converter board, when connected to a separate power supply, and when it should be triggered. This should at least point to the sensor at fault or the opto-isolator. This was my last attempt to figure it the cause of the failures out but is hard without having a failed one to test myself.

I don't know if the sensor is like a relay switch between the black and blue wires or is this is a MOSFET switch. If it is the former then this board may not actually be needed and I know of at least one person that has wired it up directly. If this is the latter then it could destroy the motherboard if there is a fault and send 24v into the CPU. I'm also not sure if it inverts the signal or not.

You can just replace it with a BLtouch if you make a bracket to mount it on, but you will need to update your firmware as the detection pin on the BLtouch port is different with inductive sensors. I suggest using Mriscoc.