The circuit of the Micro-controller based Tachometer requires the user to point a light sensitive probe tip atop the spinning shaft towards the spinning blade, disk or chuck and read the rpm. The only requirement is to first place a contrasting color mask. A strip of white adhesive tape is ideal on the spinning object. It should be positioned in such a manner that the intensity of light reflected from the object’s surface should change upon rotation. Each time the tape spins past the probe, the momentary increase in reflected light is detected by the photo-transistor.

  The circuit of the Micro-controller based Tachometer requires the user to point a light sensitive probe tip atop the spinning shaft towards the spinning blade, disk or chuck and read the rpm. The only requirement is to first place a contrasting color mask. A strip of white adhesive tape is ideal on the spinning object. It should be positioned in such a manner that the intensity of light reflected from the object’s surface should change upon rotation. Each time the tape spins past the probe, the momentary increase in reflected light is detected by the photo-transistor.