PNP Inductive Sensor and wiring

ajcraig99

Thanks,

So I read through that page and measured the resistance between each wire.
results in the image below, If I use the 10k value as R1, should I be wiring it up like the bottom diagram?

dc42

See the wiki page on connecting Z probes. You don't normally need the pull-up resistor.

ajcraig99

@dc42

I have read the wiki countless times. I should be able to plug it straight in with a reversed diode on the signal wire for protection.
I don't know why sigxcpu suggest I install a pull-up resistor, I don't know what an open collector is but I have read through the link he/she posted and am still none the wiser but am willing to try anything.

I have the new NPN sensor wired up currently as per the wiki and my image below.

With the Z_PROBE_IN disconnected, The LED is on when not sensing and turns off when near a metallic object. Indicating I have a NC sensor.
with the Z_PROBE_IN connected, The LED is on regardless of it sensing or not, It dims very slightly when near a metallic object. The duet does not sense a change when using M558 P1 or P4

sigxcpu

Maybe @dc42 says that pull-up is not required because Duet already has one. Basically, you connect brown (+) to V+ (do more than 5V because those senors like more), blue (-) to GND just like in your schematics. The black (output) wire is connected through a diode (put the line of the diode towards your sensor).

When the sensor is not activated the signal line of the Duet stays at Duet's 3V3 because of the internal pull-up. When sensor is triggered, the last NPN transistor shorts the signal (its collector) to ground (its emitter).

In theory, no diode will be required, but if the sensor has also an internal pull-up (not open collector) it will push its V+ with higher voltage towards Duet's signal and nasty things can happen.

Measure the voltage on Duet's signal pin when triggered and not triggered in your last schematic. Untriggered should be ~3.3V and triggered should be ~0V.

ajcraig99

Update:

I spent way to long thinking I was more stupid than I am trying to get this to work.
Ordered another sensor, exact same model number and it works perfectly. I think I might be using the wrong diode though because it reads 715 when triggered instead of 1000 but it still seams to work so I'm happy.

Thanks for everybodys patience.

Jeremy Watkins

Not to hijack the thread, but I am also trying to wire an inductive sensor on my older Duet Wifi (I think I am version 1.01). My dilemma is my sensor is a PNP NO DC6-36V, but my fans are 5v fans (can't easily switch them either because I am using a specialized 20mm centrifugal fan due to size constraints on my effector). So I am pretty sure that rules out connecting to the always on fan connections. I have found an abundance of cheaper 5V DC NPN sensors on Amazon which would fit my physical setup, but I am not sure if I would need to use a different diode than a BAT43 or BAT85. The sensor I am considering is a LJ12A3-4-Z/BX-5V.

dc42

@jeremy-watkins, if using a 5V NPN sensor then you don't need the diode.

Jeremy Watkins

@dc42 Thanks, I'll give that a try then! Brown to V-FAN with the jumper on 5v, blue to GND, and black to Z PROBE IN. No voltage divider needed either?