Sub-$10 sound card photogate variants

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Connecting the sensor to the microphone input

PhotoTransistor
Ambient light phototransistor (TEPT4400) connected to the 3.5mm jack.
The microphone input of the sound card should be used.
PhotoTransistor
LED
Infrared phototransistor (SFH309F) connected to the 3.5mm jack.
Heat shrink tubes are used to isolate the wires from directly touching them.
The light source can be a flashling, alternatively one can use an infrared LED (like the SFH409) connected to the USB port.

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