Posted in إلكترونيات

Shadow Activated Circuit

This circuit is used to activate an alarm if you wave  your hand in front of it:

http://www.discovercircuits.com/circuit-solutions/circuit-solu5.html

How does the circuit operate?

It contains two photo diodes facing each other that produce certain current level. This current is then converted to voltage. Once the light intensity changes, voltage in turn changes to activate the alarm.

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