Optical Bedlevel sensor for K8200/3Drag by tanteju

Last crawled date: 3 years, 1 month ago

There are several types of bedlevel sensors around. With the K8200 or 3Drag you are constantly running out of I/O-Ports and so some of those sensors are a real challenge (e.g. those with servos).
Furthermore I did not want to install more wires and thought, the three available should be sufficient.
So, here is a optical bedlevel sensor, based on IR reflection. It includes a microcontroller to make the measurements based on IR pulses and eliminate environmental IR (e.g. the heated heatbed). And still the microcontroller does have ports free. One input port is unused and two I/O ports, which could be used as I2C bus. Plus the controller does have plenty of space, RAM and EEPROM unused. Plenty of room for your imagination, what to do with that.
Be careful with the connector to the controller board. The 3Drag/K8200 does have plus on the middle pin and needs a bridge to get 5V there. RAMPS boards have two different setups. Please verify, before connecting.
The holder for the IR reflexive sensor fits on the K8200/3Drag extruder with the screws already in place. The electronics could be mounted directly to the holder, as shown in the pictures. Existing screws should fit. The holder measures are for the E3Dv6 hotend, but should be fine for the original hotend as well.
Update 18-Mar-2015
Due to some feedback on low-reflective surfaces I've uploaded a second plan "Adapterboard v2" and new PIC program. This setup swaps Emitter/Collector of the Phototransistor and uses a 47k resistor. Lower impedance gives much higher scan frequency, but it makes it harder to adjust correctly. It should give good enough signal on low-reflective surfaces as well. I've included a moving average filter for better stability.
My repeat values are better than 0.1mm, but with 90° heated it becomes tricky, as 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 06-Apr-2015
As I got two broken holder during prints, because of loose material at some edges, I've created another version: 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 same, but emitter and collector are swapped. So, please double-check and verify with yours.