Page 23 - Electronics Starter Kit_EN

Lesson 4: Light up an LED in Darkness With

Transistor and Photoresistor

4.1 Overview

In this lesson we are going to build a smart system, this circuit will light up an LED in the dark.

4.2 Components Required

1 x Breadboard Power Supply
1 x 9V Battery
1 x 9V Battery Connector
1 x Breadboard 830p
1 x 5mm red LED
1 x 220 Ω resistor
1 x 100 KΩ resistor
1 x 2N2222 NPN Transistor
1 x Photoresistor (Photocell)
3 x M-M wires (Male to Male jumper wires)

4.3 Component Introduction

Photoresistor

We can say LDR (Light Dependent Resistor), it is simple to use, has only two terminals.

The resistance of the LDR will fall with increasing light intensity and vice versa.

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