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DiscoverCircuits.com -- Hobby Corner
Last Updated on:
Wednesday, June 02, 2021 04:19 AM
Hobby Circuits List
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LINK to Dave's circuit, but DO NOT COPY any files to your WEB
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Timer Circuits
Lamp Controls
Control Circuits |
Closet Light
with Automatic 3 Min Timeout
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The
circuit below is powered by three 1.5v alkaline AA cells. With a finger tap to
the pushbutton trigger switch, a cluster of 6 wide angle white LEDs is turned on.
The lights remain on for about 3 minutes, then will turn off. This hobby
circuit’s standby current is only a few microamps. A set of fresh batteries
should last at least 200 light applications. |
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This hobby circuit uses a Schmitt
trigger inverter and two transistors. When the pushbutton switch S1 is pressed,
the 10uF capacitor C1 is discharged. When the switch is released, the capacitor is
charged through R1. With the capacitor C1 discharged, the Schmitt trigger output swings
to 4.5v, which turns on transistor Q2. The combination of R4 and Q1 form a constant
current control circuit. The current is set about 15ma per LED. When the
capacitor charges up to about 2.3v, the Schmitt trigger changes state, turning off the
LEDs. |
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Click on Circuit Below to view PDF of Schematic |
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