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.



  • I experienced this as well on my Ender 3 with OEM ribbon cable. This cable is about 1m (3ft) long.

    The X Endstop light glows dimly whenever the stepper motor is holding and the endstop is not closed. Disconnecting the sensor from the ribbon cable does not eliminate, but disconnecting the ribbon cable from the X endstop pins on the board does.

    The firmware correctly reads the state. The glow does not appear after turning it on. Engaging/disengaging the endstop has the expected/normal visible effect. Calling X Home causes the glow to begin, while disabling the stepper by calling M18 X eliminates the glow.

    I assume it is caused by the length of the adjacent runs as described in an earlier reply here.

    20200617_170340.jpg


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