Optical Bedlevel sensor for K8200/3Drag

thingiverse

There are multiple bedlevel sensor types out there. With the K8200 or 3Drag you constantly run out of I/O-Ports, making some sensors a real challenge (e.g. those with servos). Furthermore, I did not want to install more wires and thought that the three available would be sufficient. So here is an optical bedlevel sensor based on IR reflection. It includes a microcontroller to make measurements based on IR pulses and eliminate environmental IR (e.g. heated heatbed). And still, the microcontroller has free ports. One input port remains unused while two I/O-ports which could be used as I2C bus remain free. The controller also has plenty of space, RAM and EEPROM left over. Plenty of room for your imagination as to what to do with that. Be careful with the connector to the controller board. The 3Drag/K8200 has a plus on the middle pin which needs a bridge to get 5V there. RAMPS boards have two different setups; please verify before connecting. The holder for the IR reflective sensor fits perfectly onto the K8200/3Drag extruder using the existing screws. The electronics could be mounted directly onto the holder as shown in the pictures. Existing screws should fit just fine. Update: Due to feedback regarding low-reflective surfaces, I have uploaded a second plan, called "Adapterboard v2," along with a new PIC program. This setup swaps Emitter/Collector of the Phototransistor and uses a 47k resistor. A lower impedance gives much higher scan frequency, but it becomes harder to adjust correctly. It should provide good enough signal on low-reflective surfaces as well. I have included a moving average filter for better stability. My repeat values are under 0.1mm, but with 90 degrees heated it becomes tricky because the temperature has an effect on the IR and the PIC. The PIC has an internal thermistor so you could compensate this, which is not included in the program. There is a pushbutton in the plan which is not used in the program; it is intended for better adjustment of threshold. Update: As I have two broken holders during prints because of loose material at some edges, I've created another version called v03. It is 1mm shorter and includes two supports for better stability. Print with more than 25% infill as the long lever makes it a weak part if it touches edges of the piece. Important: There are two different versions of the CNY70 available. They are mostly the same, but emitter and collector are swapped; so please double-check and verify yours.