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.  Disconnect the Z probe from the "Z-STOP" port on the Printrboard.  Next disconnect the Y end stop from the "Y-STOP" port on the Printrboard and plug it into the now available "Z-STOP" port.  Lastly, plug the Z probe into the "Y-STOP" port.

                                              

 

After "swapping" your probe and Y end stop.  Send the M119 command again.  See the table below for diagnosis on which components may need replacing.

 

Wiring 

Configuration

X-STOP (M119)

Y-STOP (M119)

Z-STOP (M119)

Printrboard 

Functionality

Probe/End Stop 

Functionality

Normal open open open FUNCTIONAL FUNCTIONAL
Normal open open TRIGGERED UNDETERMINED UNDETERMINED
Y & Z swapped open open TRIGGERED BAD FUNCTIONAL
Y & Z swapped open TRIGGERED open FUNCTIONAL BAD
Y & Z swapped open TRIGGERED TRIGGERED BAD BAD

 

 

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6 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
    Avatar
    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
    Avatar
    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
    Avatar
    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

     

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