Optointerrupter

The optointerrupter consists of a light emitting diode (LED) and a phototransistor with a 3.18 mm (1/8") slot between them.

It comes with the following parts:

1. 3 ft of hook-up wire (1 piece or precut pieces)
2. Flat opaque disk with four blades (you need to cut it out)
3. Resistor 270 Ohm (used to limit the current through the LED)
4. Resistor 4.7 K (to be connected between the emitter of the phototransistor and ground/negative wire)
5. 2 sequins

Refer to the Motor With Optical Control and Assembly Instructions: Kit #7 pages for more information on how to use the optointerrupter and other supplied parts.