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Arduino Basics

Random function example

by shedboy71
written by shedboy71

In this example we use the RGB led again but are introducing a couple of new programming topis. We introduce the switch case structure and the random and randomSeed functions. We are using the same circuit as before, here it is as a reminder

RGB to ARduino

RGB to ARduino

The following is from the reference documentation, rather than rewrite the wheel here is an explanation.

The switch…case controls the flow of programs by allowing programmers to specify different code that should be executed in various conditions. In particular, a switch statement compares the value of a variable to the values specified in case statements. When a case statement is found whose value matches that of the variable, the code in that case statement is run.

The break keyword exits the switch statement, and is typically used at the end of each case. Without a break statement, the switch statement will continue executing the following expressions (“falling-through”) until a break, or the end of the switch statement is reached.

randomSeed() initializes the pseudo-random number generator, causing it to start at an arbitrary point in its random sequence. This sequence, while very long, and random, is always the same.

If it is important for a sequence of values generated by random() to differ, on subsequent executions of a sketch, use randomSeed() to initialize the random number generator with a fairly random input, such as analogRead() on an unconnected pin.

The random function generates pseudo-random numbers.

Lets look at the example, we will generate a random number from 0 to 6 (remember the random number starts at 0 unless you state a min and max number), the randomSeed to help generate a truely random number and a switch case to flash the RGB led in a particular sequence

Code

[codesyntax lang=”cpp”]

int redPin = 11;
int greenPin = 10;
int bluePin = 9;
 
 
void setup()
{
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);  
  randomSeed(analogRead(0));
}
 
void loop()
{
  int randColour = random(7);
  switch(randColour)
  {
    case 0 :  setColour(0, 255, 255); 
              delay(1000);
              break;
    case 1 :  setColour(255, 255, 0); 
              delay(1000);
              break;   
    case 2 :  setColour(255, 0, 255);  
              delay(1000);
              break; 
    case 3 :  setColour(0, 255, 255); 
              delay(1000);
              break;   
    case 4 :  setColour(255, 0, 0); 
              delay(1000);
              break;  
    case 5 :  setColour(0, 0, 0); 
              delay(1000);
              break;   
    case 6 :  setColour(128, 128, 128); 
              delay(1000);
              break;  
    default:  setColour(255, 255, 255); 
              delay(1000);
              break;               
  }

}
 
void setColour(int red, int green, int blue)
{
  analogWrite(redPin, red);
  analogWrite(greenPin, green);
  analogWrite(bluePin, blue);  
}

[/codesyntax]

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Arduino Basics

Basic RGB LED example

by shedboy71
written by shedboy71

An RGB led is basically 3 LEDs in the one package, a red, green and blue one which either share a common cathode or a common cathode. Using one of these LEDs you can create a variety of different colours simply by switching on and off various LEDs, PWM which we will discuss later also works well here. Lets look at an RGB LED

rgb led pinout

rgb led pinout

You will need the following, I used a low cost RGB LED breakout.

1 Arduino UNO
1 RGB LED
1 1k resistor
Some connection wire
1 Breadboard

The connection is fairly straightforward we simply connect the common anode to VCC via the resistor and the cathodes are connected to 3 digital pins , you can see these clearly in the code example below

[codesyntax lang=”cpp”]

int redPin = 11;
int greenPin = 10;
int bluePin = 9;

[/codesyntax]

Here is the schematic

RGB to ARduino

RGB to ARduino

Now as this is a common anode type, a high on the digital pin will switch the LED off and a low will switch the LED on. If you had a common cathode you would need to reverse the values. Lets show you what I mean.

We use the following

 

[codesyntax lang=”cpp”]

setColour(0, 255, 255); // red

[/codesyntax]

Which in turn calls the following function

[codesyntax lang=”cpp”]

void setColour(int red, int green, int blue)
{
analogWrite(redPin, red);
analogWrite(greenPin, green);
analogWrite(bluePin, blue); 
}

[/codesyntax]

As you can see from the example above the red LED is on (low), the green and blue LED is off. So you will see red. You can in fact put a variety of values in to see different colours on the RGB led

Code

[codesyntax lang=”cpp”]

int redPin = 11;
int greenPin = 10;
int bluePin = 9;
 
 
void setup()
{
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);  
}
 
void loop()
{
  setColour(0, 255, 255);  // red
  delay(1000);
  setColour(255, 0, 255);  // green
  delay(1000);
  setColour(255, 255, 0);  // blue
  delay(1000);
  setColour(0, 80, 0);  // purple
  delay(1000);
  setColour(255, 0, 0);  // aqua
  delay(1000);
  setColour(0, 0, 0);  // white
  delay(1000);
}
 
void setColour(int red, int green, int blue)
{
  analogWrite(redPin, red);
  analogWrite(greenPin, green);
  analogWrite(bluePin, blue);  
}

[/codesyntax]

 

Links
10PCS/LOT WS2812 RGB LED Breakout Module For Arduino

100 x Emitting Diodes RGB Led 5mm led diode

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