User Manual

65
Lesson 12 Photo-interrupter
Introduction
A photo-interrupter (as shown below) is a sensor with a light-emitting component and light-
receiving component packaged and placed on face-to-face. It applies the principle that
light is interrupted when an object passes through the sensor. Therefore, photo-interrupters
are widely used in speed measurement.
Components
- 1 * Raspberry Pi
- 1 * Breadboard
- 4 * Jumper wires (Male to Male)
- 1 * Network cable (or USB wireless network adapter)
- 1 * Dual-color LED module
- 1 * Photo-interrupter module
- 2 * 3-Pin anti-reverse cable
Experimental Principle
Basically a photo-interrupter consists of two parts: transmitter and receiver. The transmitter
(e.g., an LED or a laser) emits light and then the light goes to the receiver. If that light beam
between the transmitter and receiver is interrupted by an obstacle, the receiver will detect
no incident light even for a moment and the output level will change. In this experiment, we
will turn an LED on or off by using this change. The schematic diagram: