Inductive sensors as endstop 24V



  • Hi all,
    i am planning to use Inductive sensors as endstop on all axis.
    My System is running on 24V and i would like to run the sensors on 24 V.

    What do i have to do not to burn my board?

    Thanks for help.



  • https://mertarauh.com/2017/01/18/dont-trust-the-internet-and-how-to-add-an-inductive-proximity-sensor-to-your-3d-printer-the-proper-and-easiest-way/

    For NPN NO (normally open) the easiest way is to add a diode in series (beware of the polarity).



  • thanks alot....looks quite easy.



  • What voltage are you inductive sensors rated for? I've found that 6-36 and 10-30v inductive sensors work fine running on 5v:

    Proof that they work:
    https://youtu.be/Bov87qlX0Gs
    Proof that the readings are reliably repeatable:
    https://youtu.be/_-fAMAnn3_s

    So, if you are using this type of sensor, you don't need to worry about it, just plug them into the 5v sensor port, and job's a good'un.



  • me again 🙂
    i tried it with the diodes now.....
    unfortunally non of the diodes worked properly.
    non dropped the voltage below 0 always around 1.2 V which the duet doesnt measure as triggered.
    by accident i used a diode which i measured in non triggered state 22.6 V by mistake i connected it to the board and it works.... nothing burned.
    does that mean the duet has no problem with 22.6 v on that PIN?

    i am a bit confused 🙂



  • You need a Schottky diode (for boards up to rev 1.3)
    From the documentation:

    NPN output normally-open inductive or capacitive sensor
    Duet 2 Maestro, or revision 1.04 or later of Duet WiFi or Duet Ethernet: you can connect the output of the sensor directly to the Z-probe IN pin.

    Other Duets: Connect the output wire of the sensor to the cathode of a diode, and the anode of the diode to the Z probe IN pin. The diode should preferably be a small-signal Schottky diode such as BAT43 or BAT85, but a small signal silicon diode such as 1N4148 works for some people.

    All Duets: Connect the sensor ground wire to a ground pin on the Duet, and the sensor's + power wire to a suitable voltage (typically to VIN because these sensors usually need between 6 and 30V power).

    Select mode 5 (P5) in the M558 command, also include parameter I1 in the M558 command.



  • @whosrdaddy said in Inductive sensors as endstop 24V:

    You need a Schottky diode (for boards up to rev 1.3)
    From the documentation:

    NPN output normally-open inductive or capacitive sensor
    Duet 2 Maestro, or revision 1.04 or later of Duet WiFi or Duet Ethernet: you can connect the output of the sensor directly to the Z-probe IN pin.

    Other Duets: Connect the output wire of the sensor to the cathode of a diode, and the anode of the diode to the Z probe IN pin. The diode should preferably be a small-signal Schottky diode such as BAT43 or BAT85, but a small signal silicon diode such as 1N4148 works for some people.

    All Duets: Connect the sensor ground wire to a ground pin on the Duet, and the sensor's + power wire to a suitable voltage (typically to VIN because these sensors usually need between 6 and 30V power).

    Select mode 5 (P5) in the M558 command, also include parameter I1 in the M558 command.

    That only mentions the Z-Probe pin and not the endstop inputs, I would wait for clarification from Tony or David before hooking the sensor to an endstop input without the diode.



  • Yeah missed that fact.
    The endstop inputs are 3.3V and directly connected to the CPU, I believe the diode trick will still work but I don't know it will be safe...



  • I do use 24v inductive sensors on my V1.04 board with diodes without issue.



  • @tjb1 great which diode do u use ?



  • @orthocube said in Inductive sensors as endstop 24V:

    @tjb1 great which diode do u use ?

    I bought both the BAT43 and BAT85 as described here but I don't recall which one I actually used on my setup, I think I used the BAT43 as I remember the blue color but either one should work.


  • administrators

    @whosrdaddy said in Inductive sensors as endstop 24V:

    Yeah missed that fact.
    The endstop inputs are 3.3V and directly connected to the CPU, I believe the diode trick will still work but I don't know it will be safe...

    Yes the same diode connection can be used with endstop inputs as with the Z probe.


 

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