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A Beginner's Guide to Circuits by Øyvind Nydal Dahl

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4THE NIGHT-LIGHT

THIS CIRCUIT IS A NIGHT-LIGHT THAT TURNS ON IN THE DARK.

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THE CIRCUIT DIAGRAM

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THE PARTS LIST

PART

VALUE

DESCRIPTION

LDR

~10 k to ~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

R1

100 kΩ

Standard resistor

R3

470 Ω

Standard resistor

LED

 

Standard-output light-emitting diode

ABOUT THE CIRCUIT

This circuit turns on an LED when it gets dark. During the day, the light stays off, but at night, it can help ...

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