Auto Bed Leveling EN

Auto Bed Leveling

How to Connect and Install sensor for Auto Bed Leveling.


On this page, I describe how I have done to install and connect the ABL (Auto Bed Leveling) sensor. I will write ABL in the text as it is easier.

I will also try to write and describe what changes I made in Marlin (RC8).

In the text I will link to other pages with information that can make everything easier.

Hope this can help someone else want to install ABL.



To follow my guide, you need the following components.


-4N25 OPTO ISOLATOR WITH TRANSISTOR OUTPUT Vdc = 2500 (or equivalent). Länk

-Sensor LJ12A3-4-Z/BX. Länk (I use a capacitive sensor when I have a glass disk on my printer).

-1 Kohm resistance. Länk (I have obtained a rate with resistance Länk).

-Contact Z-min connection.

-Cables of the appropriate type.

-Shrink tube ("Krympslang").

-Soldering iron.

-Marlin3DprinterTool. Länk Program that facilitates work.



I have had some problems during the installation work and getting a sensor for ABL to work. They started searching online and found a lot of information about how to do and what's right and wrong.


Before proceeding with this, I think you should read the following page to understand that everything you read online is not right, but you have to know what they are about before moving on. Länk


Please watch the following YouTube video as well. Länk

Balluff sensor.

I use a sensor from Balluff when I had this home's home. This is a capacitive sensor that you can adjust the reading distance on. I chose this sensor also because I have a gaskas on my bed and a "regular" inductive sensor does not feel glass.

You can use an inductive sensor, but I recommend that you have a reading area of ​​at least 8mm. This is not a standard area, so it can be difficult to get hold of.

Coupling scheme.

Here to the left you will see a connection diagram of how to loosen and connect the components.

The sensor has three cables.

-A BRUN 12V from the control card.

-A BLUE GND (Earth) on the control board.

-An BLACK Signal.

On SVART cable from the transducer, you can resist a 1 Kohm of resistance.

On the other side you will find a cable that you then tap on Pin 1 on the Optocopler.


On Pin 2 on the Optocopler, you are loosening a cable that you mix with the BLUE cable from the sensor, which goes to the GND on the control board.


Pin 5 on Optocopler fixes cable that comes from the S Z-min on the control board.


On pin 4 on the Optocopler, a cable is attached that comes from the GND Z-min on the control board.

Cable from sensor to control card.

To the left you will see my ready-made cable that I use today.

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