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Auto bed leveling circuitry for PNP as opposed to NPN

Posted by printerguykw 
Auto bed leveling circuitry for PNP as opposed to NPN
September 01, 2016 11:20PM
I was watching Thomas's guide on auto bed tramming [www.youtube.com]

However I purcharsed a PNP sensor as opposed to an NPN sensor... [www.ebay.ca]

I'm stuck with this thing now and I'm trying to get it to work. All the guides online show circuitry from NPN sensor....I do however have multiple NPN transistor 2N2222a if that will help. Thomas' Auto Bed Tramming guide on how to wire it , I'm left with the ground wire that is to be used as the Z signal...i guess.. here is a pic that i got from instructibles that matches my setup: [i.imgur.com]

I've noticed that even though i followed the wiring guide for an NPN inductive sensor, the light from the inductive sensor does turn on when it's near the aluminium heated bed, and turn off when it is away from the aluminium heated bed.

However the wire i'm left with to use as a signal to the RAMPS 1.4 board from my inductive sensor appears to be a negative terminal. As I undertstand it, I need to send a positive signal, and I'm not sure how to invert a negative/ground signal to positive.

I'm hoping somebody can draw up a quick diagram on how to do this correctly for my case.

Thanks
Re: Auto bed leveling circuitry for PNP as opposed to NPN
September 02, 2016 10:35AM
I'm using a 12v relay board: [www.amazon.com] Using the relay output just like a mechanical endstop. Any delay caused by the relay doesn't affect it's operation.
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