3THE COOKIE JAR ALARM

THIS ALARM BUZZES WHEN IT SENSES LIGHT.

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THE CIRCUIT DIAGRAM

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THE PARTS LIST

PART

VALUE

DESCRIPTION

LDR

200 kΩ

Light-dependent resistor (photoresistor) with around 5 to 10 kΩ resistance in light and 200 kΩ or more in dark

Q1

BC547

Any general-purpose NPN transistor

R2

1 kΩ

Standard resistor

Buzzer

 

Active buzzer that works with a 9 V battery

ABOUT THE CIRCUIT

Do you want to keep people from stealing cookies from your cookie jar? Or keep spies from snooping in your treasure chest? Then this circuit is for you. ...

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