Any z probe that only occupies Z Probe connector port?

  • @deckingman said in Any z probe that only occupies Z Probe connector port?:

    Metrol precision positioning

    does it retract?

  • @veti said in Any z probe that only occupies Z Probe connector port?:

    @deckingman said in Any z probe that only occupies Z Probe connector port?:

    Metrol precision positioning

    does it retract?

    Short answer - no.

    Long answer - it's a bit complicated but in essence I use the nozzle as a probe. The hot end assembly has steel dowels which fit into oil impregnated bronze bushes on the carriage. So the hot end is constrained from any X or Y movement but is free to slide in Z (against a spring). The switch is mounted such that it is normally "made" but when the bed rises, it pushes the nozzle up which breaks the switch. It only takes about 0.4mm of movement.

    The dowel and bush arrangement means that I can quickly swap between the 3 hot end assemblies that I have. The mechanics wouldn't be for everyone - getting freedom of movement in Z whilst being constrained from any X or Y movement needs a bit of precision. But wiring is simple - it's just a switch (albeit a very precise and highly repeatable one).

    I wrote it up on my blog a couple of years ago

    and there are some pictures and stuff in the section on my printer build - about half way down here

  • or a bltouch with the resistor cut so that it can run at 3.3v

    Is it so? Does the Z Probe connector have the servo control output that the bltouch needs?

    Documentation says to use a signal from the 50 pin extender connector for this purpose.

  • @zapta The BLtouch will need to be connected to a heater pin to allow for servo control.

  • @veti There a post about this? I was searching to see if there was a way to make that work, but there are a lot of posts about BLTouch so it makes finding that info difficult.

  • @phaedrux
    my bad i got a duet maestro and the z probe in is pwm capable. on the duet wifi it is not.

  • Ya I have a BLTouch, works great but my OCD is annoyed by only using half of the Z port and some of the expansion.. 🙂 I guess I could get a Duex. Was curious about the other sensors out there too. I grabbed the BL and haven't looked at others, though I am seeing a variance in trigger height that might make others desirable if price is right.

  • administrators

    On the Duet WiFi/Ethernet: the only types of Z probe that need more than the Z probe connector are BLTouch (which also needs a servo control signal and 5V power), and other probes that need either a servo control signal or a power source greater than 3.3V (for example, most inductive and capacitive sensors need at least 6V, although a few need only 5V).

    On the Duet Maestro, the Z probe connector also carries +5V and a servo control signal.

  • The BLTouch is a little sensitive to motion during probing. It helps to add a bit of a pause after the travel move to allow it to settle. You can also increase your tolerance of probe consistency so that it will probe a few times until it's accurate.

    M558 P9 H3 F100 T6000 A10 R0.5 S0.003 B1 ; P9 for BLTouch, dive height 3mm, probe at 100mm/min, travel 6000mm/min, up to 10 probes, pause 0.5s, heaters off during probing

  • administrators

    Some bed heaters generate enough magnetic field to affect BLTouch too. So if you probe with the bed hot, you might want to use the M558 B parameter to turn off the heaters during probing.

  • Is there a way to repurpose one of the pins of duet wifi 50 pin extender connector as a Z stop input?

    Motivation: I made a small prototype board that plugs into the extender connector and provides a connector for the 3 wire part of BLtouch (gnd, +5v, servo output). If I can use one of the signals as Z stop input I can have instead a 4 pin connector that provides all the BLTouch need.

  • administrators

    If you don't have a DueX connected, there are 5 endstop pins available on the 50-way connector, and you should be able to use one of them. Caution: they are not 5V-tolerant! Use a 10K series resistor to help protect the pin. In firmware 2.02 the M558 command allows the selection of any endstop pin when using P4.

  • Thanks @dc42. I will give it a try.

    My BLTouch is set to 3.3 output (confirmed by measurement) so I presume it will be ok. My goal is to have a breakout mini board that plugs into the extender connector and has a 5 pins connectors compatible with BLTouch.

  • @dc42 said

    In firmware 2.02 the M558 command allows the selection of any endstop pin when using P4.

    Thanks dc42. The documentation says to Cn but only with P4. My Z config uses P9 for BLTouch. Can Cn be also specified for P9?

    ; Z-Probe
    M574 Z1 S2                                   ; Set endstops controlled by probe
    M307 H3 A-1 C-1 D-1                          ; Disable heater on PWM channel for BLTouch
    M558 P9 H5 F120 T6000                        ; Set Z probe type to bltouch and the dive height + speeds
    G31 P500 X20.5 Y12.9 Z0.3                    ; Set Z probe trigger value, offset and trigger height
    M557 X10:290 Y10:290 S35                     ; Define mesh grid

  • administrators

    That's a good point. Cn is only supported for P4, because most of the other modes use the Z probe connector.

  • Thanks @dc42. Any chance of enabling Cn also for BLTouch?

    My plan is to have a small breakout board that plugs into the extender connector and has a Z Probe connector that is compatible with BLTouch.

    Will post the PCB on OSH Park so people can get it easily.

  • administrators

    I don't even know whether the BLTouch will drive a Duet endstop input. I have not seen any documentation describing it the drive capability of BLTouch, and there are multiple versions of BTouch and its clones. So I can't recommend using an endstop input for BLTouch unless you use a logic gate or transistor to buffer the signal, in order to guarantee meeting the pulldown current requirement of the Duet endstop input.

    Also bear in mind that next time we revise the Duet WiFi/Ethernet, we will probably expand the Z probe connector to be 5-pin so that a BLTouch can be connected to it directly, as it can on the Duet Maestro.

  • @dc42 I would enjoy that. Not a fan of nor hater of the bltouch, but it's what I setup first, so unless I have a big reason to change it out, it will stay. 🙂


Looks like your connection to Duet3D was lost, please wait while we try to reconnect.