Object Detection Sensors

Photoelectric Interruption Sensors

These sensors detect a change in light intensity or color due to interruption by and object (beam break).

The Adafruit 5 mm IR Break Beam Sensor has an emitter and receiver that can detect an interruption by an object when separated by up to 50 cm (20 inches) apart. A related product is the 3 mm IR Break Beam Sensor that allows the emitter and receiver to be up to 25 cm (10 inches) apart. See a project using the 3 mm IR break beam sensor.

A laser emitter and receiver product such as this Twidec E3F-20DNL-18 product allows the emitter and receiver to be as far as 20 ft (6 m) apart. Other products can be found that are NC (normally closed) and NO (normally open). Taiss 0 to 20 m (65 ft).

Tutorial: IR Sensor Module Circuit includes how to use an OpAmp as a voltage comparator with a IR LED and Photodiode.

Inductive Sensors

Used to detect the presence of metal objects.

Capacitive Sensors

Detect the presence of objects that have a dielectric constant that is different than air. In general they are limited to a range of 1 to 20 mm.

Ultrasonic Sensors

Sound waves are emitted and the signal reflected back is analyzed to detect the presence and distance to an object. Commonly used for non-contact liquid level detection where sound wave transmission is optimal.

Radar Sensors

Microwave or radio frequency signals are emitted and then the reflection back (time in flight) is measured to determine the position of the item being measured.

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