In these days, were 3D printing is getting more and more popular, and 3D-printer freaks is constantly talking about the perfect "First layer", I have invested in an inductive sensor for a perfect bed leveling. The problem is that it runs on 12 volts and the microcontroller can only handle 5 volts. I could easy make a over-engineered, with lots of additional features, but I chose the simple solution, and just made en simple level shifter.
Step 1: The Ramps 1.4 Design and the Level Shifter Design
I quickly saw a solution, were I could use power from the E1 socket, you would use if you have two hotends, but I have not. I used the 12 volt pin to power the inductive sensor, and the 5 volt pin to use as the output voltage to the microcontroller. I could also use the step or the direction pin as the Z- min endstop pin, thus I don't have to use a jumper to the normal Z-min endstop. If I could prevent more wires on a ramps, the would be great!
I have made a circuit diagram, where all you need is included. You can check my EasyEDA page to see the print layout and the BOM: https://easyeda.com/razzer_n/inductive-sensor-leve...
I have made the design with smd parts to make it look less like a "dead bug". I have also included some solder jumper pads, so you can chose between the step, the dir and the classic Z-min endstop pin.
Step 2: Setup and Config
If you use this setup, you must check the high and low state of the sensor. If you didn't already new it, this type of level shifter inverts the high signal to a low and vice versa. You may have to invert the high and low in software. Remember to change the Z-min endstop pin to the E1-dir(D34) or E1-step(D36) if you change the inductive probe to one of there pins.