PNP NO inductive sensor

  • In the Duetwifi Wiki, it says to use a combination of resistors to get the voltage output of the signal wire to 3 volts when triggered. I have a sensor that I was using with my ramps board just fine with 4.88 volts at the signal wire when triggered. I could only find 22k and 33k resistors locally and that combination brings it down from 12v to 4.88v. Is 4.88 really going to be too much for the Duetwifi? Could I just add another resistor to the signal wire to reduce an additional 1.8 v?

  • administrators

    4.88V is unlikely to harm the Duet, but we can't promise it because it relies on the ESD protection diodes in the processor working properly.

    If you connect another 22K resistor in parallel with the existing 22K resistor, that should bring it down to 3V.

  • Thanks.

  • Make sure you measure the signal voltage under load, so attach an led, or bulb or something sometimes the sensors give odd readings when measured without any load on them.

  • There is already a 22K and a 33K resistor in there. I think those count as loads.

  • Fair enough.

  • Adding the second 22K resistor in parallel with the first brought the voltage at the signal wire down to 2.97 volts. The probe is working fine.

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