9 Photoresistor

My Photoresister experiment:

Setting Up

Setting Up


CIRC-09 Breadboard Sheet

2 Pin Header


Ohm Resistor Brown-Black-Orange

560 Ohm Resistor Green-Blue-Brown

Green LED

Fully functional

Fully functional


Fritzing Sketch:

project 9 sketch_bb2

Project Working on Video:

Project 9 from Elizabeth Agyemang on Vimeo.


Source Code:

* A simple programme that will change the intensity of
* an LED based  * on the amount of light incident on
* the photo resistor.

//PhotoResistor Pin
int lightPin = 0; //the analog pin the photoresistor is
//connected to
//the photoresistor is not calibrated to any units so
//this is simply a raw sensor value (relative light)
//LED Pin
int ledPin = 9;   //the pin the LED is connected to
//we are controlling brightness so
//we use one of the PWM (pulse width
// modulation pins)
void setup()
pinMode(ledPin, OUTPUT); //sets the led pin to output

* loop() - this function will start after setup
* finishes and then repeat
void loop()
int lightLevel = analogRead(lightPin); //Read the
// lightlevel
lightLevel = map(lightLevel, 0, 900, 0, 255);
//adjust the value 0 to 900 to
//span 0 to 255

lightLevel = constrain(lightLevel, 0, 255);//make sure the
//value is betwween
//0 and 255
analogWrite(ledPin, lightLevel);  //write the value

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