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Dark Sensor LDR Circuit

JoeJester

JoeJester

Joined Apr 26, 2005
4,390
Here is one, without values of the resistors listed, that seems to meet your specifications with a six volt battery,

LDR.png

For a buzzer, here is one under a dollar at Mouser
 

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Jony130

Jony130

Joined Feb 17, 2009
5,488
This type of a small buzzer will have a equivalent resistance around 500Ω .
Also try to do some real world measurement. Try to measure the Vce voltage (voltage difference between collector (red probe) and emitter (black probe) ) for T1 and T2 with and without the light. Also the T1 base voltage.
 
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