This document summarizes how to build a light sensor using a photoresistor (LDR) and an Arduino. It explains that Arduino is a microcontroller platform that runs programs written in C/C++. These programs use two core functions: setup() and loop(). It then describes how an LDR's resistance decreases with increasing light intensity, making it a sensor for light levels. The document provides the circuit diagram and materials needed to connect the LDR to an Arduino board via resistors to measure light levels with the Arduino's analog-to-digital converter (ADC).

1. LIGHT SENSOR BY USING PHOTOCELL
WITH ARDUINO
s u b m i t t e d b y
H u d a A l i
Under supervision of
Dr. sadiq kamel

2. What is Arduino?
Arduino is a family of microcontrollers and physical
programming platform. The first Arduino was produced in
2005. Many programs and applications usable with
arduino like: Macromedia Flash, Processing, Max/MSP, Pure
Data, Super Collider, C# ……. Can be purchased and you
can easily practice.

3. Arduino programs are written in C or C++.
Users only need define two functions to make a runnablecyclic
executive program:
•setup(): a function run once at the start of a program that can
initialize settings
•loop(): a function called repeatedly until the board powers off

4. LDR
 p h o t o r e s i s t o r o r p h o t o c e l l . I t s
r e s i s t a n c e c h a n g e s w i t h t h e l i g h t i n t e n s i t y
t h a t f a l l s o n i t .
 T h e r e s i s t a n c e o f a p h o t o r e s i s t o r d e c r e a s e s
w i t h i n c r e a s i n g i n c i d e n t l i g h t i n t e n s i t y. I n
o t h e r w o r d s , i t e x h i b i t s p h o t o c o n d u c t i v i t y.
 T h e r e s i s t a n c e r a n g e a n d s e n s i t i v i t y o f a
p h o t o r e s i s t o r c a n s u b s t a n t i a l l y d i f f e r
a m o n g d i s s i m i l a r d e v i c e s

5. Circuit symbol
of LDR
A typical
LDR

6. Materials
• Arduino MEGA/ Other Arduino Cards
• Breadboard
• 220 ohm resistor
• 1K ohm resistor
• Jumper Cable
• LED
• LDR

7. Schema

8. Schema

9. ADC IN ARDUINO
Digital number Volt
1 4.8 mV
10 28 mV
100 480 mV
208 1 V
417 2V
1023 5V

10. Code

11. Project Related Images

12. Project Related Images