3.1 Light Sensor Intro


Light is an important environmental property that shapes the ecosystems around us. During the day when the sun is out, light availability is high. At night, after the sun sets, the availability of light is low. This daily light cycle affects many living things like plants or algae which depend on sunlight to grow and animals that have behaviors like hunting or sleeping which are influenced by cycles of light and dark. In indoor areas, measuring light can also be important to figure out the best spot to put a house plant or test the brightness of various light bulbs types.

Materials Needed:

Materials needed for Basic Light Sensor Construction and Application Activities:

In addition to the materials listed above, you will need to edit the file on you microcontroller to activate the light sensor. See the instructions on our Code Resources page for how to change the active sensor.

Introduction to Light Sensors:

Light sensors detect the intensity or brightness of a light source. Light is often measured in Lumens, a which describes how much light is emitted from a source, and Lux, which describes light intensity measured over a specific area. The light sensors used in this activity digitally measure Lux by measuring the intensity of light that reaches a defined area on the surface of the sensor. 

Visible light exists on the electromagnetic radiation spectrum and has a specific range of wavelengths between about 400-700 nanometers (nm) long. On the smaller end of the spectrum, is ultraviolet light (down to about 300 nm) and on the longer end of the spectrum is infrared light (up to about 1000 nm). Light sensors often detect the intensity of light across a specific range of wavelengths. Sensors that detect the full spectrum of visible light measure light intensities across all wavelengths between 300-1000 nm. Some light sensors measure light intensities of a subset  of those wavelengths so as to measure the intensity of just ultraviolet light or infrared light.    

Figure 3.1

In this activity, you will use a digital light sensor (TSL25X1) to measure light intensity of the full visible spectrum and just the infrared spectrum.