# Auto-Leveling

Basically, it should be the same way of my previous post… to calculate which pair of resistor you should use you can check this calculator: http://www.raltron.com/cust/tools/voltage_divider.asp

For example R1 = 470 and R2 = 120 should work. Resistors are represented by squares on the schematics.

I am a little confused because from what I’ve seen the resistors should be between the output and z-min and the ground not the 24v supply. Could you explain why you said to wire it the way you did, just trying to learn more about it.

first of all: the circuit that i draw is untested, never plug an circuit without testing it on a breadboard fist.

The idea is, as you have an NPN sensor, it will sink the current. that means, current will flow through it, so when no metal is present, the circuit would let the current flow from the 24V to ground, measuring between the resistors you would measure about 5v.

When the metal is present, the sensor would cut the current flowing, and you would measure 0V between the resistors.

I’m not an electronic engineer (I’m a chemical engineer though) so this is the way i think t would work. Buttttttttttt, test it before plugin on your taz. if you feed 24V on ramboo will definitely kill it.

So after finally getting some more tools and being able to do some testing i have switched over to one of the cylindrical sensors being it will run off of 5V. Now my only problem I have is how I should mount it. I saw Techsavvy’s model (link below) but I don’t like how far it hangs off the side of the extruder assembly. I was wondering if anyone has any ideas on how I should mount it.

So I have designed my own mount, I will most likely make some more revisions but I am happy with it thus far. Below you can find a picture of the mount along with the STL. It has been working great thus far and I can’t wait to keep using it.

Mount-round2.STL (41.5 KB)

nb,

Nice job!

1. Could you source the sensor?
2. NPN or PNP?
3. How did you wind up wiring it up, Voltage reg or Resistors?

This is an NPN inductive proximity sensor. Keep in mind this only works because of the plate I have on top of my printer has a metal core, otherwise you would need a capacitance proximity sensor. I have the power wired to the 5V from the Z-MAX and the ground running to the Z-MAX also. The signal is connected to the Z-MIN signal. I was able to do this without any voltage reg or resistors because I am tapped in the the 5V. With the other sensor I had it didn’t work with 5V so I had to run it off the 24V from the power supply.

The sensor I have can be found here: http://www.ebay.com/itm/161246102208?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I believe this one should work for the stock glass build plate: http://www.amazon.com/gp/product/B008MU0G9A/ref=as_li_tl?ie=UTF8&camp=211189&creative=373489&creativeASIN=B008MU0G9A&link_code=as3&tag=techinc0a-20&linkId=4N7KHY3CJ3JBIZR3

And just incase that link expires the name is: LJ12A3-4-Z/BX Inductive Proximity Sensor Switch NPN DC

I take it was just simpler to tap into the 5v & GND off the Z-MAX? Any other reason?

Exactly, tapping into the 5V meant I didn’t need to step down the voltage compared to using the 24V. The first sensor I tried wouldn’t work off of 5V that’s why I had to switch to a different sensor. Also you don’t have to use the 5V and GND from the Z-MAX, you can take it from anyone, but this was just the most convenient place for me.