Hobby Projects - Insulation tester, LED Circuits, Meters.

Friday, December 14, 2007

Simple Cheap Dark-Detecting LED Circuit

Here's a simple problem: "How do you make an LED turn on when it gets dark?" .....Complete
Simple Cheap Dark-Detecting LED Circuit
Parts -On top: a CR2032 lithium coin cell (3 V). On the bottom (L-R): the LED, an LTR-4206E phototransistor, a 2N3904 transistor, and a 1 k resistor. This LED is red, blindingly bright at 60 candela, in a 10 mm package. It casts a visible beam, visible for about twenty feet in a well-lit room.
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