Adafruit GA1A12S202 Log-scale Analog Light Sensor

True Logarithmic Response from 3 to 55,000 Lux!

by Bill Earl

published June 22, 2013, last edited June 22, 2013

posted in Adafruit Products Sensors/ Light

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Beginner

Product guide

Assembly and Wiring

Assembly

The Adafruit Analog Light Sensor comes pre-assembled and fully tested on a handy breakout board. We have included a small header strip in case you want to use it on a breadboard. This can be installed in a few simple steps:

Position the header

Trim the header to size if needed and place long-pins-down in the breadboard.

Position the breakout board

Line the board up with the header pins and drop it in place for soldering.

Solder!

Solder each pin to assure good electrical conductivity.

Wiring for Arduino

Wiring this sensor is very simple. It can be powered by 2.3-6V, and has an analog output of up to 3v max. To use with an Arduino, wire it as follows:

VCC -> 5v
OUT -> A0
GND -> GND

SInce the output range of the sensor is 0-3v, for maximum resolution, it is best to use the 3.3v pin for your voltage reference. To do this, run a jumper from 3.3v to AREF on your Arduino. In your code, be sure to specify "analogReference(EXTERNAL);"

When using an external analog reference, it is important to specify analogReference(EXTERNAL) in your code before performing any analogRead() operations. Otherwise, your external reference will be shorted to the default internal 5v reference. This can damage your Arduino.

Standalone Wiring

One nice thing about this little sensor is that it doesn't require a microprocessor for interfacing. You can use this sensor to make simple light-activated circuits or even an analog light meter. The sensor output varies from about 5-50uA. With the on-board 68K resistor, this translates to a range of about 0.3v to 3v.