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    • Projects 1 >
      • 1.01: Blink
      • 1.02 Blink x2
      • 1.03 Blink Faster
      • 1.04 LED Chase!
      • 1.05 Wait To Blink
      • 1.06 Blink a Little Faster Now
      • 1.07 LED Fade
      • 1.08 RGB Blink
      • 1.09 Change RGB Color with SW1
      • 1.10 Fade RGB Colors
      • 1.11 Reaction Time Game
    • Projects 2 >
      • 2.01 Hello World
      • 2.02 Talk Back
      • 2.03 ASCII Values
      • 2.04 Ski Game
      • 2.05 Demonstration of the String Object
    • Projects 3 >
      • 3.01 Read the Potentiometer
      • 3.02 ASCIIbet Soup
      • 3.03 Potentiometer sets LED Brightness
      • 3.04 Potentiometer Sets Blink Rate
      • 3.05 LED Chase, Part II
    • Projects 4 >
      • 4.01 Bringing the Piezo to Life
      • 4.02 Controlling the Piezo with a Function
      • 4.03 Piezo C Major
      • 4.04 Piezo Greensleaves
      • 4.05 Piezo Metronome
      • 4.06 Piezo as an Input
      • 4.07 Piezo as an Input 2
      • 4.08 Metronome II
      • 4.09 Piezo Playback
      • 4.10 Piezo Fireworks
      • 4.11 Piezo Mosquito
    • Projects 5 >
      • 5.01 The Phototransistor
      • 5.02 Light and Sound
      • 5.03 Light and Sound II
    • Projects 6 >
      • 6.01 EEPROM
      • 6.02 I2C Address Scan
      • 6.03 Read the I2C Temperature Sensor
      • 6.04 High Temperature Alarm
    • Projects 7 >
      • 7.01 Arno Phone Home
      • 7.02 Keyboard Alphabet
      • 7.03 Move Mouse
      • 7.04 Draw Squares
    • Special Projects >
      • Bike Light Demo
  • References
    • Arno Pin Key
    • Arno Schematic
    • Project Index

Project 5.01 First Look at the Phototransistor

This is a simple sketch where we read the value from the phototransistor using the analogRead statement and output the value to the serial monitor.  The phototransistor is an analog device.  It does not give us a simple LOW or HIGH value.  The voltage on the pin connected to the phototransistor increases as the amount of light increases. Upload the program, wait a moment, and then start the serial monitor.  Hold the board close to different light sources or near a window.  When the reading reaches 1023, the phototransistor is saturated and can’t register any additional increase in the amount of light.


Concepts: analogRead, voltage divider

Circuits: 
  • Circuit 5


  • Select Sketch

    ///////////////////////////////////////////////////
    //Project 5.01 Read the phototransistor
    int photoTran = A1;
    int reading = 0;
    void setup(){
    pinMode(photoTran,INPUT);
    Serial.begin(9600);
    }
    void loop(){
    reading = analogRead(photoTran);
    Serial.println(reading);
    delay(100);
    }
    ///////////////////////////////////////////////////


    Back to Projects 5

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