A photocell senses the level of light falling on it. Comes assembled & ready for immediate connection to the Make Controller. See the photocell how-to for more information on how to connect it to the Make Controller.

Project Ideas Using a Photocell

Detection
Use a photocell to determine when a box is open or closed.

Trip Wire
Mount a laser pointer on the wall and point it at the photocell. When you break the beam, the reading from the photocell will be much lower and you know the 'wire' has been tripped.

Touch Keypad
Photocells can be used in place of keys on a specialized keyboard of your design. A person's finger will block light enough to trigger a readable change in voltage through an analog in. The controlling software can signify that the keys are "pressed" when the voltage rises above a given threshold.

Musical Instrument
Upward pointing photocells can make a nice music controller - as the hand of the user gets closer, it blocks more light reducing the value seen by the analog in port. You can use the incoming value to alter the pitch, tempo, volume or any other quantity.