Light sensor basics | Light detecting sensor types

This page describes basic function of Light Detecting sensor or Light sensor. It mentions Light sensor types and mentions light sensor inner construction with working.

Definition: It detects intensity of light and gives output according to it. It is mainly used for security reasons in office and home premises. It is also used in automatic street light system.

Light Sensor

• The light sensor is basically a passive device.
• It converts light energy (in visible or infrared spectrum) into electrical signal as shown in the figure-1.

Light sensor types

There are three types of light sensors:
• Photo Conductive cells: This type of cells vary electrical resistance when they are subjected to light signals.
• Photo Voltaic cells: This type of cells generate emf which is proportional to light energy falling on it. The most common material used in photo voltaic cell is selenium. It is used in solar cells.
• Photo Junction Devices: These devices are true semiconductor devices e.g. photo-diode or photo-transistor. These devices use light to control the flow of electrons as well as holes across the PN Junction.

Photo resistors are semiconductor devices which use light energy to control the flow of electrons, and hence current flowing through them. The commonly used photo-conductive cell is called Light Dependent Resistor or LDR.


Also refer IoT compliant sensors which includes ambient light sensor, optical sensor, gesture sensor, proximity sensor, touch sensor, fingerprint sensor etc.

Refer Sensors and transducers article which covers types, basic functions and provide links to sensors and transducers. It include temperature sensor, humidity sensor, strain sensor, proximity or occupancy sensor, force or load sensor, voltage and current sensor, pressure sensor, speed sensor, resistance sensor, power sensor, level sensor, event or state sensor etc.

Sensors and Transducers Related Links

Proximity Sensor
Occupancy Sensor vs Motion Sensor
LVDT and RVDT sensor
Position, displacement and level sensor
force sensor and strain sensor
temperature sensor
pressure sensor
Humidity sensor
MEMS sensor
Touch sensor
Haptic sensor
Wireless sensor

RF and Wireless Terminologies