A bit of thought led him to build a reflective sensor which can measure the spinning of a wheel (translated). He got his hands on an infrared phototransistor which had been used as part of the ...

Proximity sensors are common enough in automation ... The first try at this used an OBP732 reflective transmitter and an ATtiny202 microcontroller and had three pads on the PCB for programming.

Both sensors easily recognized the specially formulated, TiO 2-based paint but did not readily detect the traditional paint. The researchers say that their highly reflective material could help ...