BL-Touch Ground question



  • I have a Wanhao D6 I'm converting to use a Duet2 Wifi. I'd like to stick with the 16-wire ribbon cable that comes with the D6, but adding a BL-Touch leaves me one wire short. (Part Fan + HE Fan + stepper+ PT100 + Heater = 12, BL-Touch = 5). I was wondering if someone more electrically inclined that myself might know if I can share a ground wire between any of these components. My initial thinking is no, but maybe if I put the HE Fan on an always-on connection... Any assistance would be greatly appreciated!

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  • I share the negative wires on the BLTouch and it works just fine.

    In my case one of the BLTouch wires (black out of the three connductor connector) is just hanging in mid air.



  • Learning from my mistake when I made my own patchpanel (I too took cues from my wanhao i3 plus) do not commonly bond the gnd for the parts fan or pwm fans. The bltouch (both the black and brown ground leads) and anything else can be commonly bonded. If you’re hotend fan is always on, you can bond that too, as well as the heater. (Remember to aggregate enough pins for the fan to handle the amps needed).

    I found out that the ground for the fans are what controls them since on the duet the ground is drained as the way they are controlled. My first pass I had bonded all the grounds and that resulted in my parts fan being permanently on.



  • You can share positives on PWM fans. Gnd, as stated, is what is switched for PWM and must be unique per fan.



  • <sigh> ...... as I said, a single ground wire to the BLTouch will solve all issues .....

    Edit: In case it is not obvious, the remaining ground wire has to go to a true ground and not a switched ground like you would find on some of the output connectors.

    Edit ver 2.0: .... In my case the BLTouch is hooked up to PWM5 on the Duex board and the ground on that connector is true ground (ie not switched)
    The signal pin (White wire) is the only wire from the BLTouch that goes to a different connector (to the z probe connector, Z probe in pin)


  • Moderator

    I've never understood why the BLTouch has 2 separate ground wires.



  • I think it's because it has two separate connectors and it's somehow mandatory for an electronics person to always supply a reference ground when you have a signal line.


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