Auto-Leveling Probe: Triggered vs Open

Are you suspicious that your Auto-Leveling Probe (aka Z Probe) may be malfunctioning?  Some users have seen the Z axis go upwards when they click home or when running the Auto Leveling Process (G29).

You can run a quick test by issuing the following commands in your software.  

  • Connect
  • M119 

The read-back from your M119 command should be as follows:

  • x_min: open
  • y_min: open
  • z_min: open

The term "open" indicates that the end stops or probe are not closed or "TRIGGERED".  In the image below, you can see an example of each axis (X, Y, then Z) being homed. In this example, the M119 command is given after each axis is homed, reporting the axes being "TRIGGERED" one by one.  If your commands look like this, the end stops, probe, and Printrboard are functional.  If not, see the table below for further diagnosis.

 

 

To diagnose, power OFF your Printrbot.  Swap the wiring for your Y STOP and Z STOP connections - plugging the Auto-Leveling Probe into Y-STOP and the Y end stop into Z-STOP.

                                              

 

After "swapping" your probe and Y end stop.  Send the M119 command again.  Activate each end stop by manually trigger each end stop by pushing each axis to its "home" position one by one.  To home/trigger your Z axis, put something metal (screwdriver/pliers) near the tip of your Auto-Leveling Probe.  NOTE: Physically push the axes.  Do not use the "home" buttons on your software.  

 

See the table below for diagnosis on which components may need replacing.  

 

 

X-STOP (M119)

Y-STOP (M119)

Z-STOP (M119)

Printrboard 

Functionality

Probe/End Stop 

Functionality

open open open FUNCTIONAL BAD
open TRIGGERED open BAD FUNCTIONAL

 

 

Have more questions? Submit a request

10 Comments

  • 0
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    Bill Mallon

    so if your setup is normal and the probe reads TRIGGERED, what do we do?

  • 0
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    Dave - PB Support Team

    Hi Bill, I apologize if I misunderstand your question, but if your setup is normal and the probe reads "TRIGGERED", that matches line 2 of the table.  To discern if either the probe or the board has an issue, swap the Y and Z end-stop connections and match your results to lines 3, 4, and 5 in the table.

    Hope that is hepful,

    Dave

  • 0
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    Bill Mallon

    Hi Dave unfortunately this does not solve my issue. As far as I can tell the sensor has simply gone bad the indicator light on top that normally only lights up when it's with 4mm of the print bed (or any metal) is on permanently and the M119 query gives a triggered result regardless of whether the probe is near any metal. I've tried plugging it into the Y stop header as well as a 5v fan header on my PC and get the same result, The light is stuck on and the sensor is apparently stuck always triggered. 

  • 0
    Avatar
    Dave - PB Support Team

    If you used swapped the probe to the Y stop header (in addition to a fan header on your computer), it sounds like you essentially matched the scenario in line 4 "Y & Z Swapped":

     

     

  • 0
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    Bill Mallon

    HI Dave, since my last message I ordered another probe and that one seemed to work initially. The printer would home Z and auto-level correctly. However a few minutes afterwards the printer began experiencing, essentially the same problem. The only difference now is the LED on top of the probe is not stuck on. The light only comes on when the probe is near metal, suggesting that it's at least partially functional. However as long as it's plugged in M119 shows the Z-Stop as triggered, regardless of whether the sensor is near anything metallic. Also if I unplug the new sensor and plug it into the Y-Stop, M119 shows the Y-Stop as triggered, indicating this newest sensor is also damaged. Is it possible the Printrboard has suffered some kind of damage where the voltage coming off the Z-Stop jumper is damaging the sensor in some way?

  • 0
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    Gfmail

    My issues have some parallels with Bill's. My Simple Metal is 2y old and has over that time worked reliably always printing while connected via USB. A few weeks ago I started having prints that inexplicably stopped in the middle. I suspected some USB issue although there have been no changes to cables or the computer. As a work-around I started printing directly from the uSD card. That worked fine for a while although I seemed to be having more extruder clogging when trying to start a 2nd print after completing one. Finally, while trying to restart after having to abort a print where the filament was no longer feeding I found I could no longer lower (home) the z-axis. The extruder will move up but never down.

    I followed the steps outlined for troubleshooting the probe. After both the normal and swapped wiring configurations, the results indicate that both the Printrbot board and the probe are bad. My questions are, before ordering both a replacement board and a replacement probe:

    1. Are there any other tests I should perform to confirm the diagnosis?

    2. What are the likely causes of this multiple failure?

    Thanks for your help,  George

     

  • 0
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    Dave - PB Support Team

    @Bill - "Is it possible the Printrboard has suffered some kind of damage where the voltage coming off the Z-Stop jumper is damaging the sensor in some way?"

    A: I suppose anything is possible, but after speaking with our electronics guy, it doesn't sound likely that the probe is damaged.  However, I may have aided you in misdiagnosing the probe as the culprit.  If you replace the board and find that your original probe is good, please let us know by submitting a ticket for RMA and reference this forum post.

     

  • 0
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    Miguel Sanchez

    I am kind of experiencing a somehow similar problem caused after a spark jump from my finger to the printer while connected to USB (and to ground from there). 

    The probe LED responds to my approaching a metal to the bottom of it. M119 responds too, but now it says triggered whenever the LED is OFF and open whenever the LED is ON. I guess I will need to reload the firmware to get it working back to normal. 

    I hope this may help.

  • 0
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    Miguel Sanchez

    I grabed this firmware https://github.com/Printrbot/Marlin

    And changed line 258 of Configuration.h to 

    const bool Z_MIN_ENDSTOP_INVERTING = false;

    Now I am a printing happily with the same hardware (now M119 gives the right output, triggered when metal is detected and led is on, open otherwise).

    Edited by Miguel Sanchez
  • 0
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    Dave - PB Support Team

    Thanks Miguel!

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