Arduino projects1.docx

Simple Labs' Quick Start Kit for Arduino - LED Interfacing - How To?

The world of LEDS

LEDs (Light Emitting Diodes) are the most commonly used of electronic components. They are everywhere – torches, displays, indicators, etc. Every project will eventually end up having atleast one led. The Official Arduino Boards and most of the Clones do come with an on-board LED which you can try with the default blink program found in the File->Examples->Basic menu of Arduino IDE.

So How to Connect a LED?

The Long of the LED is the Anode (Positive Terminal!) and the short led is the Cathode(Negative Terminal). 

Programming to control the LED

So how can you control a LED? Well there are only 2 ways to control an LED. you can either switch it ON / OFF or you can control the intensity with which it glows (Very much like a fan!). So lets see how to do the first control - ON/OFF (we can call this digital control! Very much 0s & 1s)

Try the following code. [Blink.ino]

 /* 

  Blink  

  Turns on an LED on for one second, then off for one second, repeatedly.  

  This example code is in the public domain.  

  */ 

 void setup() {         

  // initialize the digital pin as an output. 

  // We have our LED connected to Pin 11 

  pinMode(11, OUTPUT);     // Sets the 11th pin as an Output pin

 }  

 void loop() { 

  digitalWrite(11, HIGH);  // set the LED on 

  delay(1000);       // wait for a second 

  digitalWrite(11, LOW);  // set the LED off 

  delay(1000);       // wait for a second 

 } 

Next, Lets see how to control the intensity of the LED.

The Intensity can be varied by controlling the voltage applied to the individual pins. If you take a look at the 11th PIN on the arduino, you would see a marking 'PWM' next to it (Remember we connected our LED to the 11th pin). The PWM pins in addition to generating digital HIGH / LOW signals can generate analog voltages between 0 & 5.

The PWM Pins [Pins 3,5,6,9,10,11] that can generate a PWM signal of 8-bit resolution.[8-bits can represent a maximum value of 255, and a 8-bit resolution here means that 5 volts is represented by 255 divisions. So if you want to generate 1 volt, you would use the value 51]

The analogWrite function will take a 8-bit numerical value as a parameter [called duty cycle] and produce an output voltage corresponding to this value. It will set the pin to generate a steady square wave of the specified duty cycle at roughly 490Hz frequency.

Finally, when using a pin in the PWM mode, we don't have to use the pinMode() function.

Try the following code with the same setup and see how the intensity increases and decreases...[Intensity.ino]

 /* 

  Intensity 

  Increases the Intensity of a LED from 0 to maximum and on reaching maximum

  starts decreasing back to 0

  */ 

 int intensity = 0;

 void setup() {         

 }  

 void loop() { 

   while(intensity < 255) // Check if intensity has reached maximum value, if yes then exit the loop

   {

     analogWrite(11,intensity);

     delay(25);

     intensity++;

   }

   while(intensity > 0) // Check if intensity has reached minimum value, if yes then exit the loop

   {

     analogWrite(11,intensity);

     delay(25);

     intensity--;

   }

 } 

Simple Labs' Quick Start Kit for Arduino - RGB LED Interfacing - How To?

The RGB LED

The RGB led aka the tricolor led is a led that can help generate a multitude of colors by mixing red, blue & green colors. Its more like 3 leds (red, green & blue) put together into a single led.

It has 4 pins with 1 of the pins being a common cathode and the other 3 pins acting as anodes for the 3 different colours. by varying the intensity of each of the 3 colours individually, we can generate various colours. This led is the same as 1 pixel of a LED TV!.

Here is how to wire it up

Now try the following code first. This code is a normal digital control of all the three colors separately.[RGB_Blink.ino]

/*

  RGB_Blink

  Turns on each of the color spectrums for 4 seconds, repeatedly.

  */

void setup() {               

  // initialize the digital pins as an output.

  pinMode(11, OUTPUT);

  pinMode(10, OUTPUT); 

  pinMode(9, OUTPUT); 

}

void loop() {

  digitalWrite(9,LOW);

  digitalWrite(11, HIGH); 

  delay(4000);             

  digitalWrite(11, LOW);   

  digitalWrite(10, HIGH);

  delay(4000);             

  digitalWrite(10, LOW);   

  digitalWrite(9, HIGH);

  delay(4000);          

}

Next Lets get generating Colors, try the following code. Play around with the values and get yourselves comfortable.[RGB.ino]

/* RGB

 Sets some random intensity value to the various colours of...