Assignment: Sensing: Potentiometers

Collaborators:

Assignment: Sensing: Potentiometers
Collaborators:

Assignment: Sensing: Potentiometers
Collaborators: Becky

In this lab, we used potentiometers to control LED output.  First, we connected one potentiometer to control the rate that one LED blinked.  Then, we connected three potentiometers.  In my example, each potentiometer controls a different LED, causing it to be fainter or brighter.

Materials:

• Arduino board
• 3 220 ohm resistors
• 3 LEDs
• wire
• 3 potentiometers
• breadboard
• usb cable
• computer
• paper (printer, tissue)

Code:

/*
* "Coffee-cup" Color Mixer:
* Code for mixing and reporting PWM-mediated color
* Assumes Arduino 0004 or higher, as it uses Serial.begin()-style communication 
* 
* Control 3 LEDs with 3 potentiometers
* If the LEDs are different colors, and are directed at diffusing surface (stuck in a
*   a Ping-Pong ball, or placed in a paper coffee cup with a cut-out bottom and 
*   a white plastic lid), the colors will mix together.
*
* When you mix a color you like, stop adjusting the pots.
* The mix values that create that color will be reported via serial out.
*
* Standard colors for light mixing are Red, Green, and Blue, though you can mix 
*   with any three colors; Red + Blue + White would let you mix shades of red, 
*   blue, and purple (though no yellow, orange, green, or blue-green.)
*
* Put 220 Ohm resistors in line with pots, to prevent circuit from 
*   grounding out when the pots are at zero
*/

// Analog pin settings
int aIn = 0;    // Potentiometers connected to analog pins 0, 1, and 2
int bIn = 1;    //   (Connect power to 5V and ground to analog ground)
int cIn = 2;  

// Digital pin settings
int aOut = 9;   // LEDs connected to digital pins 9, 10 and 11
int bOut = 10;  //   (Connect cathodes to digital ground)
int cOut = 11;  

// Values
int aVal = 0;   // Variables to store the input from the potentiometers
int bVal = 0;  
int cVal = 0;  

// Variables for comparing values between loops
int i = 0;            // Loop counter
int wait = (1000);    // Delay between most recent pot adjustment and output

int checkSum     = 0; // Aggregate pot values
int prevCheckSum = 0;
int sens         = 3; // Sensitivity theshold, to prevent small changes in 
                      // pot values from triggering false reporting
// FLAGS
int PRINT = 1; // Set to 1 to output values
int DEBUG = 1; // Set to 1 to turn on debugging output

void setup()
{
  pinMode(aOut, OUTPUT);   // sets the digital pins as output
  pinMode(bOut, OUTPUT);   
  pinMode(cOut, OUTPUT); 
  Serial.begin(9600);     // Open serial communication for reporting
}

void loop()
{
  i += 1; // Count loop

  aVal = analogRead(aIn) / 4;  // read input pins, convert to 0-255 scale
  bVal = analogRead(bIn) / 4; 
  cVal = analogRead(cIn) / 4;  

  analogWrite(aOut, aVal);    // Send new values to LEDs
  analogWrite(bOut, bVal);
  analogWrite(cOut, cVal);

  if (i % wait == 0)                // If enough time has passed...
  {    
    checkSum = aVal+bVal+cVal;      // ...add up the 3 values.
    if ( abs(checkSum - prevCheckSum) > sens )   // If old and new values differ 
                                                  // above sensitivity threshold
    {
      if (PRINT)                    // ...and if the PRINT flag is set...
      {
        Serial.print("A: ");        // ...then print the values.
        Serial.print(aVal);         
        Serial.print("\t"); 
        Serial.print("B: ");        
        Serial.print(bVal);
        Serial.print("\t");
        Serial.print("C: ");                
        Serial.println(cVal); 
        PRINT = 0;
      }
    }  
    else
    {
      PRINT = 1;  // Re-set the flag   
    } 
    prevCheckSum = checkSum;  // Update the values

    if (DEBUG)   // If we want debugging output as well...
    {
      Serial.print(checkSum);
      Serial.print("<=>");
      Serial.print(prevCheckSum);
      Serial.print("\tPrint: ");
      Serial.println(PRINT);
    }
  }
}