Faint LED on X Endstop indicator



  • Hi,

    I've recently (~2months ago) got Duet2Wifi board that I installed on Ender 3. I bought it from official reseler in Germany (makerdise). Everything works I usually manage to tune things to get very good prints but there is one thing that bothers me for a while. Namely if X motor is powered when X Axis is homed the X endstop LED with still have faint red glow meaning that some current still flows through it. If I cut the power to X motor then the light goes away. The image below shows how the light looks like when X is homed and X motor is enabled.

    IMG_20200131_095449543.jpg

    I am trying to understand if this is normal and if it is why it's happening only on X endstop?


  • administrators

    It's not normal. The only thing I can think of that would cause that problem is some sort of contamination on the top of the PCB between the LED and the adjacent X motor connector, so that if the X motor is energised there is a small amount of current leakage between the two. Can you see anything there? Can you post a close-up photo of that area of the PCB, with the motor connectors unplugged?



  • Everything seems ok to me but here is a picture

    20200202_152337.jpg

    PS. Thx for help dc. Your work on duet is much appreciated 🙂



  • I know using the wrong type of switch for home (or maybe a failed switch) can cause that LED to go from dim to bright. I had to change the poles I used on my switch I used for homing and that dim/bright led thing stopped.



  • Did a quick test before work and it seems it solved the problem but I need to check when I'm at home again. Even though this seemed to be the problem I am still confused about the relation of the Endstop LED to the current flowing through the motors.


  • administrators

    If you use normally-open endstop switches, and the X endstop cable runs in the same bundle as the X motor cable over a considerable length, then I guess it's possible that capacitance in the cable between the endstop and motor wires could cause the LED to glow dimly. Using normally-closed endstop switches will fix that (the LED will be on at full brightness when the endstop is not triggered).



  • That makes sense since it's a ribbon cable. I'll test different current levels for the motors and other endstop switches to see if it affects the led brightness. I prefer normally open switches for this use case so I'll keep them and separate the cables of necessary. Thx for the help.


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