Need help wiring end stop switches

  • Hello All!

    I two P11DMB-DLD Metrol positioning switches with the idea of using them in a large format 3D printer (think 4' x 4' x 4'.) The switches themselves only have two leads (blue and brown) and I believe they need to be wired according to the following diagram:

    How can I correctly wire the switches to the Duet Ethernet?



  • The switch has a built-in LED, so the diagram on the right should be correct.

  • Additionally, if I test continuity across the two wires with a multimeter, the LED lights up. If I push the button while testing the continuity, the LED will turn off.

  • administrators

    Switches with series LEDs don't work in low voltage (3.3V) switching circuits because the voltage drop of the LED is too high. However, if you wire them the wrong way round (so that the LED doesn't light up) or bypass the LED, then you should be able to use them as ordinary NC microswitches. Alternatively you could use an NPN transistor to interface each one to an endstop input.

  • @kzamani As David has pointed out, switches with series LEDs don't play nicely with end stop inputs. As it happens, I use a very similar Metrol precision switch for my Z axis but had to set it up as a type P1 analogue probe. I did a bit of write up on my blog which you might find interesting It was a couple of years ago so some of the information might be a bit out of date. But you could at least use one of the switches as a Z probe but you need to arrange the mechanics such that the nozzle has some degree of movement in the Z direction which being constrained in both X and Y.

    BTW these are excellent switches - the repeatability is quite remarkable. In hindsight, I should have bought the non-LED version.

  • Thanks @dc42 & @deckingman ! I've ordered a few resistors and I'll post back when they come in. Thank you both for the quick responses and thank you Ian for the informative blog post! That really helped.


  • I found success by wiring the Blue wire to GND and the Brown cable to the "in / XYZ stop" pin.


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