OpenBuilds Limit Switch reads hit in (S1) and (S0)



  • Hello,

    I am trying to use this OpenBuilds limit switch with my Duet.

    https://openbuildspartstore.com/xtension-limit-switch-kit/

    I chose this limit switch because it connects physically very well on the openbuilds components my printer is built out of. However, when setting it up it reads "yes" when not physically triggered in both the active high and active low scenarios. When I depress the switch in either S1 or S0 configuration it changes state to "no". Is this limit switch not compatible with the Duet system?

    (sorry, I know limit switch questions are very tedious - but was curious if anyone else might have experience with this OpenBuilds product in a Duet environment.)



  • it says normally open, so you should probably have to disable the pull up on the board, or if the pull ups are hard wired provide a stronger pull down?
    (or see if you can find a schematic for the switch, at glance i couldn't)



  • @bearer Many thanks for this insight. While I couldn't locate a schematic drawing I was able to snap this detailed image (attached) of the tiny PCB the switch is attached to which may shed some light. However, I'm awful with this type of thing, so any insights from all of you more knowledgeable folks is much appreciated.

    Of course I am happy to just get different types of switches if this is going to be too problematic using this one.

    00100lrPORTRAIT_00100_BURST20200122114813299_COVER.jpg



  • @tom_lauerman said in OpenBuilds Limit Switch reads hit in (S1) and (S0):

    Of course I am happy to just get different types of switches if this is going to be too problematic using this one.

    It should work, if wired and configured correctly. Do you have a multimeter? If so try measure continuity between supply and signal, then between ground and signal. Repeat with switch pressed.



  • Perhaps try ! or not, ^ or not, and the variant combinations thereof.


  • administrators

    It's probably similar to the Makerbot mechanical endstop, which is covered in the wiki page about connecting endstop switches.



  • With the makerbot versions I found removing all the surface mount components left me with a normally closed switch. Works fine for me, but you would loose the noise filtering which would place more emphasis on wire routing, and other electro magnetic interference management techniques such as shielding, twisted wire pairs etc.

    I'd raised the request for a configurable threshold voltage on the limits switches rather than plane on-off years ago but not sure it is possible without Duet hardware re-work.

    Edit: Reverse engineer the circuit diagram before stripping components to ensure this will work for you too!


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