https://www.cnlanbaosensor.com/m12-metal-capacitve-proximity-sensor-cr12cf02dpo-2mm-diameter-10-30vdc-pnp-cable-product/
Wholesale M12 Metal Capacitve Proximity Sensor CR12CF02DPO 2mm diameter 10-30VDC PNP Cable...
Description Lanbao capacitive sensors are used for detection of both metal and non-metal (plastic, powder, liquid, etc.);M12 series clindrical capacitive...
https://hackaday.io/project/193539-capacitve-human-interface-devices
Capacitve human interface devices | Hackaday.io
An STM32 HID system that uses captive touch input to register keyboard input.
human interfacedeviceshackadayio