Green Light Go

This is a very simple sensor. Whiskers can be made out of simple metal wire, which can be connected to the Arduino. When a whisker touches an object, the object pushes the whisker to another metal contact which is also connected to the Arduino. This closes a circuit, just like a switch.

In this example, the Arduino will enable LEDs corresponding to the whiskers when they are activated.

								// "Whisker" / Bump Sensing Example

								// Refer to LED pins using a name instead of a number
								int LED_R = 11;                      // Red LED is on pin 11
								int LED_G = 12;                      // Green LED is on 12

								// Refer to whisker pins using a name instead of a number
								int WHISKER_L = A4;                  // Left whisker is on analog 4
								int WHISKER_R = A5;                  // Right whisker is on analog 5

								void setup() {                       // setup() - called once at the beginning
								  pinMode(LED_RED, OUTPUT);          //   We are outputting data to the LEDs
								  pinMode(LED_GREEN, OUTPUT);

								  pinMode(WHISKER_L INPUT);          //   And receiving data from the whiskers
								  pinMode(WHISKER_R, INPUT);

								  digitalWrite(WHISKER_L, HIGH);     //   Set a default value for the whiskers
								  digitalWrite(WHISKER_R, HIGH);     //   This prevents environment noise
								}

								void loop() {                        // loop() - called repeatedly
								  if(digitalRead(WHISKER_L)==LOW){   //   If the left whisker is bumped
								      digitalWrite(LED_R, HIGH);     //     Turn ON the red LED
								  }else{                             //   If it's not bumped
								      digitalWrite(LED_R, LOW);      //     Turn OFF the red LED
								  }

								  if (digitalRead(WHISKER_R)==LOW){  //   If the right whisker is bumped
								      digitalWrite(LED_G, HIGH);     //     Turn ON the green LED
								  }else{                             //   If it's not bumped
								      digitalWrite(LED_G, LOW);      //     Turn OFF the green LED
								  }
								}

The photocell is a semiconductor whose electrical resistance is dependent on the amount of light shining into it.

In this example, the photocell is connect to an analog pin, so that its value can be read. With that information, the Arduino adjusts the brightness of the LED.

								// Photocell Example

								void setup(){                       // setup() - called once at the beginning
								  pinMode(A0, INPUT);               //   We'll read the photocell on Analog pin 0
								  digitalWrite(A0, HIGH);           //   Set a default value

								  pinMode(3, OUTPUT);               //   We will control the LED on pin 3
								  digitalWrite(3, 0);               //   Turn the LED off
								}

								void loop(){                        // loop() - called repeatedly
								  int value = analogRead(A0);       //   Read the photocell's value

								  float percent = (float)value/340; //   By experimenting, we found that 340 is
								                                    //   about the highest possible value
								                                    //   So we'll calculate a number as a
								                                    //   percentage of 340

								  int output = 255 * percent;       //   The highest value we can send to the
								                                    //   LED is 255, so find the % of that

								  if(output > 255){                 //   If, somehow, we've calculated a higher
								    output = 255;                   //   number than 255, cap it.
								  }

								  analogWrite(3, output);           //   Turn the LED on and off really fast
								                                    //   So fast, the LED seems dimmer/brighter
								                                    //   Higher values = LED on longer
								                                    //   0 = off, 128 = 50%, 255 = 100%
								}
							

Infrared light is invisible to the human eye, but not to this sensor. By shining IR light and detecting its reflection, the sensor can determine how close or far an object is.

In this example, the distance is measured first and a far object activates the green LED. A somewhat close object activates the yellow LED, and a very close object activates the red LED.

The servo sweeps the sensor back and forth, giving it a great field of view. This is optional.

								// IR Proximity Sensing Example

								#include <Servo.h>            // Load a library which makes it really easy to
								Servo myServo;                // control a servo.

								void setup(){                 // setup() - called once at the beginning
								  pinMode(A0, INPUT);         //   Read the distance sensor on Analog pin 0

								  pinMode(2, OUTPUT);         //   Pin 2 controls the green LED
								  pinMode(3, OUTPUT);         //   Pin 3 controls the yellow LED
								  pinMode(4, OUTPUT);         //   Pin 3 controls the red LED

								  myServo.attach(9);          //   Pin 9 controls the servo
								  myServo.write(0);           //   Set the servo to 0 degrees
								}

								int dir = 1;                  // Keep track of which direction we're turning
								int pos = 0;                  // Keep track of current servo position

								void loop(){                  // loop() - called repeatedly
								  int led_r = 0;              //   Only one LED will be enabled. Assume all
								  int led_y = 0;              //   will be turned off until we know which one
								  int led_g = 0;              //   will be turned on

								  int value = analogRead(A0); //   Read the current distance

								  if(value < 100){            //   If the distance is small
								    led_r = 1;                //     we should enable the red LED
								  }else if(value < 500){      //   If the distance is moderate
								    led_y = 1;                //     we should enable the yellow LED
								  }else{                      //   If the distance is large
								    led_g = 1;                //     we should enable the green LED
								  }

								  digitalWrite(2, led_r);     //   Update the LED's
								  digitalWrite(3, led_y);
								  digitalWrite(4, led_g);

								  if(pos > 179){              //   If the servo is far right then
								    dir = -1;                 //     we should start moving left
								  }else if(pos < 1){          //   If the servo is far left then
								    dir = 1;                  //     we should start moving right
								  }
								  pos += dir;                 //   Increase the position in the correct direction

								  myServo.write(pos);         //   Tell the servo where it should be
								  delay(20);                  //   Do nothing for 20ms (gives time to move)
								}
							

A transistor can function like a switch which we can be controlled electronically.

In this example, the Arduino controls the speed of a motor by rapidly flipping the "switch" off and on using Pulse Width Modulation.

								// DC Motor Control Example

								void setup() {                // setup() - called once at the very beginning
								  pinMode(A2, INPUT);         //   Potentiometer's value is read on Analog pin 2
								  pinMode(3, OUTPUT);         //   Motor speed is controlled using Digital pin 3

								  digitalWrite(3, 0);         //   Turn the motor off initially
								}

								void loop() {                 // loop() - called repeatedly
								  int value = analogRead(A2); //   Read the current value (10 bits)
								                              //   NOTE: We can only send 8 bits of data to the
								                              //     analogWrite function below. So we must the 2
								                              //     least significant digits from the value we
								                              //     read in.

								  value = value << 2;         //   Drop the 2 least significant digits

								  analogWrite(3, value);      //   Flip the transistor on and off really fast
								                              //   Higher values = transistor on longer
								                              //   0 = off, 128 = 50%, 255 = 100%
								}
							

In this example, a potentiometer acts as an analog input, and the servo acts as an output.

A potentiometer is a resistor whose value can be altered by turning a knob.

The Arduino will sense the position of the potentiometer and rotate the servo to match.

								// Example
								#include 
								Servo myServo;

								void setup() {                // setup() - called once at the very beginning
								  pinMode(A0, INPUT);         //   Potentiometer's value is read on Analog pin 0
								  myServo.attach(9);          //   The servo's control signal is sent on digital pin 9
								}

								void loop() {                 // loop() - called repeatedly
								  int value = analogRead(A0); //   Read the current value (10 bits (0-1023))
								                              //   NOTE: We can only send 8 bits (0-255) of data to
								                              //     the analogWrite function below. So we will map
								                              //     one range onto the other
								                              
								  value = map(value, 0, 1023, 0, 255);

								  myServo.write(value);       //   Move the servo!
								                              //   Higher values = larger angle
								                              //   0 = 0 degrees, 128 = 90 degrees, 255 = 180 degrees
								}