ARDUINO IR REFLECTANCE ALARM Using Homemade Sensor

Photoelectric sensors detect objects and surface changes using variations in optical properties.

- T.K. HAREENDRAN

Each sensor includes a light emitter and a receiver, with most relying on infrared light. In optical proximity sensing, the emitter and receiver are housed in the same unit.

An infrared reflectance sensor, also known as a diffuse sensor, detects changes in reflected light from a target. This variation alters the light received, which is then converted into an electrical signal. Some of these sensors and modules, widely available at electronics retailers, are shown in Fig. 1. The components required to assemble the device are listed in the Bill of Materials table.

Note. A compact analogue reflectance sensor such as the CNY70 was not used in the Arduino Uno experiments described. Instead, a homemade sensor was assembled using a single infrared LED (IR333C) and a commonly available phototransistor (PT908-7C-F). Fig. 2 shows the homemade reflectance sensor.