NPN (NO) Z Probe problems. (Read the wiki)

  • (Pic link below)

    Okay so I've been wrestling with this for a couple days now. I have an NPN probe set up here, and it seems like I have the wiring right, when I move metal near the probe the light on both it and the Duet E0 light up, so it seems like a signal is getting to the board.

    Here's a photo of what I did, just for sanity testing -

    I'm guessing that my issue here is something dumb on my part with the firmware so I'm pasting a copy of the endstop code here so someone can hopefully tell me what I'm doing wrong.

    ; Endstops
    M574 X2 Y2 Z0 S1 ; Define active low and unused microswitches
    M558 P4 I1 X1 Y0 Z1 H5 F120 T6000 ; Set Z probe type to switch, the axes for which it is used and the probe + travel speeds
    G31 P600 X24 Y24 Z2.5 ; Set Z probe trigger value, offset and trigger height
    M557 X15:275 Y15:275 S20 ; Define mesh grid

    The probe is hooked up to E0, and the firmware is set to P4, as per the wiki. And again, both the board E0 LED and the trigger LED on the probe light when you try to trigger it.

    Help me Obi Wan etc.

  • administrators

    Does the Machine Properties page of DuetWebControl and/or the M119 command show the probe as triggered when the LEDs are on, or as not triggered?

    What type of diode did you use? Some people have found that they need to use a Schottky diode, not an ordinary silicon diode, because of the voltage drop.

  • Yeah it's not triggering. I ordered a box of BAT85 which will be coming tomorrow. I went to a local place today and picked up some 1n3600jp ones and was using one of those. It's also a 200ma/30v but it IS silicon, however.

    So I guess that is probably the issue then? Thing lights up, board lights up. I will, however, say that the LED on the board, when triggered, is dimmer than the other endstop LEDs by a fair amount.

    I'll try again when the other diodes show up tomorrow.

    Thanks much for the info.

  • I found with my opto-endstops initially I was using too small flags which resulted in the dim leds when physically triggered but no triggered status in console. So it sounds as though your sensor isn't getting close enough to 0v to trigger it. Can you measure the voltage when triggered?

  • administrators

    If the endstop led is dimmer than the others, that suggests excessive voltage drop him the sensor+diode.

    Another fix would be to connect the diode to the In pin on the Zprobe connector instead of to E0, and to select probe type 1 or 5. Ideally you would also add a pullup resistor between In and 3.3V, but it might work without that when using type 5.

  • Okay switching it to the correct diode did the trick! Thanks so much for the help!

  • Wanna say thanks again and show my work -

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