Objective

In this project, we will use Raspberry Pi to get light strength data with photoresistor . As raspberry pi can not handle analog input, we need an A/D adapter to convert analog voltage into digital signal. You can  select either MCP3008 ,MCP3204 or  MCP3208 module as  A/D adapter. In our experiment, we selected MCP3208.

Parts and Devices

Devices
qty
Raspberry pi2/3
1
8GB MicroSD memory card preinstalled Raspbian OS.
1
GPIO breakout kit(optional)
1
A/D adapter
1
photoresistor
1
10K ohm resistor
1
breadboard
1
jumper wires
some

Circuit Connection Graph(MCP3208 or MCP3008):

MCP3208 and MCP3008 are very similar, the datasheet of these two modules are sa following:

MCP3008 datasheet:http://osoyoo.com/driver/MCP3008_datasheet.pdf

MCP3204/MCP3208 datasheet:http://osoyoo.com/wp-content/uploads/2016/10/MCP3208_datasheet.pdf

Circuit Connection Graph(MCP3204):

Install software:

1.  connect your Pi to internet and then install GIT with following terminal command: 
sudo apt-get install git-core

If there is any error during git installation, run following commands  first, then do GIT installation again.
sudo apt-get update
sudo apt-get upgrade
2. download wiringPi library installation package with GIT
git clone git://git.drogon.net/wiringPi
If you need updated wiringPi, run following commands:
cd wiringPi
git pull origin
3. Build wiringPi library
cd wiringPi
./build
4. Download sample code by running following command:
wget  http://osoyoo.com/wp-content/uploads/samplecode/raspi_photoresistor.c
5. compile sample code with following command:
gcc -Wall -o  app  raspi_photoresistor.c  -lwiringPi
6.run the code:
sudo  ./app
After running the sample code, your pi terminal will show light value as following:
 2016-12-17-041356_1440x900_scrot

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