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Lesson 9 Photoresistor
Overview
In this lesson, you will learn how to measure light intensity using an Analog Input and use the
level of light to control the number of LEDs to be lit up.
Components Required
Name Qty Name Qty
UNO R3 or MEGA 2560 1 LED 8
Breadboard 1 220Ω Resistor 8
74HC595 IC 1 10KΩ Resistor 1
Photoresistor (Photocell) 1 DuPont Wire 19
Component Introduction
A photoresistor is a light-controlled variable resistor. The resistance of a
photoresistor decreases with the increasing incident light intensity; in other
words, it exhibits photoconductivity.
Connection Schematic
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
GND
VCC
DS
OE
ST_CP
SH_CP
MR
Q7'
220R
220R
220R
220R
220R
220R
220R
220R
UNO R3/
Mega 2560
74HC595
AREF
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11
D12
D13
GND
SDA
SCL/RESET
3V3
5V
A0
A1
A2
A3
A4
A5
GND1
GND2
VIN
Analog Input
Digi tal Input/Output
ARDUINO-NOHOLE
10K
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