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This hobby circuit has been used in some museum displays and exhibits when the electronics
needed to trigger an audio/visual presentation is behind a plastic or glass panel. A finger pressed against the glass, over a designated
area triggers the switch.
Infrared light reflected off a finger is used to activate this switch circuit. Drawing only
30uA from a 3v supply, this electronic circuit will detect a human finger with a range of about 1 inch. The sensor uses an inexpensive
infrared LED and a matching photo diode. The circuit is immune to ambient light. |
