|
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. |
