http://www.electronics-tutorials.ws/io/io_4.html http://www.electronics-tutorials.ws/io/io_4.html Photo Resistors Photo-geek catnip. http://www.electronics-tutorials.ws/io/io_4.html Light Sensor, Photocell and LDR Sensor Photo-geek catnip. The Light Sensor a very useful resource http://www.electronics-tutorials.ws/io/io_4.html «Light Sensors» http://www.electronics-tutorials.ws/io/io_4.html electronics-tutorials.ws/io/io_4.html http://www.electronics-tutorials.ws/io/io_4.html