BLTouch on fan or heater pins on Duet Wifi



  • I read the fantastic instructions on https://betrue3d.dk/bltouch-on-duet-wifi-configuratio-and-usage/#wiring
    but I want to use just Duex5 for my 5 drivers & heaters for the extruders and cannot use the expansion header either. That's why I am looking for potential (PWM capable) alternative heater and fan pins on the Duet board. Here's where I'm stuck:

    • How would I setup the wiring (3 bltouch vs 2 board pins)?
    • What are the right pins for using a fan for PWM? P20 or P22 returns an error.
      (I know I need to disable the heater pins first. No idea if/how to disable fan pins though..)

  • administrators

    https://duet3d.dozuki.com/Wiki/Using_servos_and_controlling_unused_IO_pins covers how to disable fans to make their pins available.



  • Thx @dc42 .
    And how can I wire the bltouch to 2pins? Ground I get, but are the other pins polarity neutral?
    Are there any other pins than the ones listed PWM capable?


  • administrators

    You would need to connect the FAN- pin to the bltouch control wire and also connect a pull-up resistor between that wire and +5V. It will need to be a fan connector on the Duet, not on the DueX5. Don't connect to the V_FAN pin of the fan connector.

    Are you really using all 8 heater outputs?



  • @dc42 said in BLTouch on fan or heater pins on Duet Wifi:

    Are you really using all 8 heater outputs?

    No, I am not using all 8 heater outputs. But for the sake of a cleaner setup (all 5 extruders on duex), I opted to go this path.

    The gcode I found here does not work as you cannot use M106 to control a servo (anymore)

    Edit: I finally found a way to use BLTouch on a fan output.
    Just to have it documented for others:
    I am using Fan2 on Duet Wifi to control BLTouch. Follow the excellent instructions on https://betrue3d.dk/bltouch-on-duet-wifi-configuratio-and-usage

    There are 2 differences in my setup:
    In config.g replace
    M307 H7 A-1 C-1 D-1 ;Disable the 7th Heater to free up PWM channel 5 on the Duex board.
    with
    M106 P2 I-1 ; Disable fan 2 for BLTouch PWM

    In deployprobe.g use
    M280 P22 I1 S10 ; use this when connected to fan 2

    retractprobe.g use
    M280 P22 I1 S90 ; use this when connected to fan 2

    If you choose another fan, for example fan 0, change config.g such as
    M106 P0 I-1 ; Disable fan 0 for BLTouch PWM

    and in deploy and retract scripts
    M280 P20 I1 S10 ; where Pn corresponds to PIN number, not fan number as outlined here

    Here is a picture of my wiring:
    IMPORTANT: connecting the PWM Fan2 wire to the V_FAN pin (marked with an X) will most likely fry your BLTouch!!!

    0_1538310614231_63b74d40-51e7-48c7-ac80-ebef80b4e99b-image.png

    For the 5V connection, I recommend using at least a 23 or even better a 25 connector for better reliability and to prevent wrong polarisation.


  • administrators

    Do you have it working now?



  • @dc42 Yes!
    Struggling with tool-changing macros now... Don't seem to call any of them in 2.02RC2...


  • administrators

    Did you home the printer first? Tool change macros are not called if axes are flagged as not homed.



  • Hi, I'm trying to copy your work into my project.
    Unfortunately I've to deal with 8 Heaters: 4 Beds and 4 Extruders.
    I'm having the 'new' version of BL Touch

    I tried to use the FAN2 as it seems promissing.
    The probe is doing it's self-test but doesn't react to any retract, deploy messages.
    Even when I just try to send the M280 P22 I1 S10 ; M280 P22 I1 S90; manually.

    As the Heater pins are working, I guess I missed something else...
    Right now I don't have access to my scope, so I'd like to avoid any risky actions..
    My first guess:
    May it be possible that I have to put a pull-up resistor between 5V and the PWM of the FAN?

    Note to all guys: Yeah 4k7Ohm Pullup to 5V is resolving that issues

    Sorry for bothering you, next time I'll considering checking the Circuit before asking.
    BTW: Thanks for the idea with the Fan PWM Googliola
    Cheers,
    Roland


  • administrators

    @fallenhorseman said in BLTouch on fan or heater pins on Duet Wifi:

    Hi, I'm trying to copy your work into my project.
    Unfortunately I've to deal with 8 Heaters: 4 Beds and 4 Extruders.
    I'm having the 'new' version of BL Touch

    I tried to use the FAN2 as it seems promissing.
    The probe is doing it's self-test but doesn't react to any retract, deploy messages.
    Even when I just try to send the M280 P22 I1 S10 ; M280 P22 I1 S90; manually.

    As the Heater pins are working, I guess I missed something else...
    Right now I don't have access to my scope, so I'd like to avoid any risky actions..
    My first guess:
    May it be possible that I have to put a pull-up resistor between 5V and the PWM of the FAN?

    Note to all guys: Yeah 4k7Ohm Pullup to 5V is resolving that issues

    Sorry for bothering you, next time I'll considering checking the Circuit before asking.
    BTW: Thanks for the idea with the Fan PWM Googliola
    Cheers,
    Roland

    That's right, the fan outputs are open-drain so to use them as servo outputs you need a pullup resistor to +5V.



  • @fallenhorseman Glad I could help.

    Note to all guys: Yeah 4k7Ohm Pullup to 5V is resolving that issues

    Funnily, I dont need a pullup between 5V and the PWM of the FAN, but I need one between GND and Z-Probe (as you can barely see in my picture 😉 . I use the 'old' version of BLTouch which is not 3.3V 'tolerant'. Am I missing something or is that a typo on your side?


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