IR sensor dead?



  • I am using IR sensor with MKS Gen 1.4 board. It was working fine. I was having a 3d printed mount for the IR Sensor. Auto bed leveling with 9 points was enabled in Marlin and it worked fine

    Last week I gave a big print of Eiffel tower by night. After 20%, the print collapsed and print became noodles of the structure. In that, it hit the IR sensor and broke the 3d printed mount. When I check in the morning, the sensor was lying in the bed.

    Now I am trying to connect. But LED light was not at all glowing. I checked the continuity of the wires, that is fine.

    How to troubleshoot? Thanks


  • administrators

    The most likely failure causes are:

    • The plastic cover on the LED has got sheared off. Does the output from the sensor still response to a nearby surface?
    • The phototransistor or one of the two IR diodes has been sheared off (the phototransistor in particular comes off quite easily). Can you see any component missing? Note, C1 is deliberately missing except on older sensors.


  • 0_1545899788699_IR Sensor.jpeg

    Thanks. I hope the Q1 is missing 😞

    I checked the schematic and found that Q1 is SFH 3015 FA-Photo transistor. I hope it will be available locally. Is it possible for us to replace?


  • administrators

    Yes, the phototransistor is missing. The part number is SFH3015FA. It's available from electronic component distributors including RS Components, Digikey, Mouser. When you fit it, make sure you install it the right way round. The white square on the PCB should be the same end as the green mark on the phototransistor.



  • @dc42 Ok. Thanks for the quicker updates as always. 👍 👍


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