ward1e

Here are the links to the data sheets for anybody interested: FDC1004DSCT - I2C - 0.5 pico farad precision capacitive sensor http://www.ti.com/lit/ds/symlink/fdc1004.pdf LP2985A-33DBV - http://www.ti.com/product/LP2985 - 5V to 3.3V linear regulator PUSB3FR4 - https://assets.nexperia.com/documents/data-sheet/PUSB3FR4.pdf - ESD protection In theory we should be able to measure the capacitance between the aluminium fan mount plate on the ultimaker 2+ (the bottom of the fan plate lies parallel to the print bed) and the print bed to make this work. We would then need to use the i2c bus on the Arduino Mega 2560 to read from the i2c capacitive sensor. Then we need to implement an autoleveling strategy in Marlin. I'm still waiting for my pico farad precision capacitive sensor multimeter to arrive to check this approach could work.

"Don't order the capacitive sensor board! It is nothing more than a copper plane that forms one of the planes that form the capacitor that we measure in the active leveling probes. The other plane is the aluminium heater plate." Many thanks for the reply tomnagel, I was actually going to order the part tomorrow so I will hold off based on your comment. It would be super useful to know which capacitive sensor chip is involved if you can give me the manufacturer and part number? I just wanted to get the electronics sorted out for now as a starting point to see if this would be a viable way of retrofitting autolevelling to the ultimaker 2. Based on what you said I just to check I understand correctly how this works: You have 2 plates, one of which is the aluminium heater plate, the other is the other is a copper plate that is part of a PCB that integrated into the print head (the part I almost ordered). The actual process of measuring the distance between the nozzle and the aluminium heater plate works by moving the nozzle closer to the glass print bed which will cause the capcitance to gradually increase, when the nozzle collides with the glass in the print bed the trend in capacitance will change, as the print head can't physically move through the glass. This trend change is how we know the nozzle is in contact with the glass and is how the auto leveling sensor works.

Thanks for the suggestion and part number it seems 3gbire can provide one with shipping in the UK for £19.91 so I'm going to order one to take a look. This is probably a stupid question but how did you find the part number? Is there a schematic of all the parts available somewhere online? It would also be useful to know the protocol used by the board. I checked GitHub but can only find the Ultimaker2 repo.

I have attempted to measure the capacitance between the build plate and the print nozzle using a capacitance meter I had on hand. I wasn't able to observe any significant difference in capacitance when the build plate was touching the nozzle however the capacitance meter I was using can only measure down to individual nanofarads. After doing some more research into capacitive touch sensors it appears that the change in capacitance could actually be in the picofarad range. See: https://www.allaboutcircuits.com/technical-articles/circuits-and-techniques-for-implementing-capacitive-touch-sensing/ In order to test this I have ordered a more precise capacitance meter that can measure individual picofarads. If this is able to detect a significant difference my next step will be to see if a capacitive touch sensor ic such as the AT42QT1070 (it comes with a nice breakout board here https://www.adafruit.com/product/1362) can detect the 2 surfaces touching. If anybody knows which capacitive sensor ic is being used for detecting when the nozzle is touching the build plate on the ultimaker 3 that would be really helpful? (I don't have access to an ultimaker 3 to inspect the PCB.

After reading about how auto levelling works on the UM3 here: https://ultimaker.com/en/community/23463-inside-the-ultimaker-3-day-6-active-leveling As UM3 autoleveling works by basically by measuring the capacitance between the build plate and the nozzle tip I wanted to see if the same mechanism could be used on the UM2. Before I waste any time going further and attempting to measure the capacitance between the build-plate and the nozzle I wanted to know if the ultimaker community had already tried anything like this on the ultimaker 2.