My homebrew IR photogate consists of two parts, the emitter and the detector. The emitter contains an infrared LED from Radioshack, and a red LED to indicate when it has power. It uses a lens form an old laser pointer to focus the beam which increases the range by about 10%. The detector uses an infrared phototransistor in series with a 1000 Ohm resistor, and a full wave bridge to make it non-polar. When the beam is unobstructed, it registers pressed in touch sensor mode, and when the beam is blocked it registers released.
Here's a schematic. The emitter is on the right and the detector on the left.
seree (from thailand) November 28, 2009, 6:28 am
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Hey I am going to try this on my microcontroller kit. Thanks for posting this.