Solution assignment part 1

We build a very simple variant of the test programme, which you have also come across in one of the learning resources.

int redLedPin = 11; // choose the pin for the red LED
int inputPin = 12; // choose the input pin (for PIR sensor)
int val = 0; // variable for reading the PIR sensor

void setup() {
  pinMode(redLedPin, OUTPUT); // declare red LED as output
  pinMode(inputPin, INPUT); // declare PIR sensor as input
}

void loop(){
  val = digitalRead(inputPin); // read PIR sensor value
  if (val == HIGH) { // check if the input is HIGH
    digitalWrite(redLedPin, HIGH); // turn LED ON
  }
  else
  {
    digitalWrite(redLedPin, LOW); // turn LED OFF
  }
}

If all goes well, the red LED should now blink in your simulation as soon as you activate the PIR sensor (see the command for how to do this). It is striking that the LED does not go off immediately, but only after about 1 second. Apparently, it takes a while before the PIR switch indicates that there is no more movement.

Solution assignment part 2

If you run the code from this exercise, you will see that you get a printout in the serial monitor a lot of times. This is because the loop() function in your Arduino program is executed over and over again as quickly as possible. The code is made in such a way that you always get one of the two situations from your if statement. Even if your led was already switched off, it will be switched off again and again as long as the PIR sensor gives a low value. And the same goes for switching on at a high PIR sensor value. Part 3 of the assignment will show you how to prevent this.

Solution command part 3

If you execute the code from this job, you will only get a printout if you actually activate the PIR or if the PIR concludes that it sees no movement. This tactic is very often used to react to changing values (from a sensor, for example) instead of reacting when a value is high or low.

Solution Assignment part 4:

// Init the Pins used for PWM
const int redPin = 11;
const int greenPin = 9;
const int bluePin = 10;

// Init the Pins used for 10K pots
const int redPotPin = 0;
const int greenPotPin = 1;
const int bluePotPin = 2;

//Init pin for PIR sensor
const int pirPin = 12;

// Vars
int currentColorValueRed = 0;
int currentColorValueGreen = 0;
int currentColorValueBlue = 0;
int pirVal = LOW;
int pirState = LOW;


void setup()
{
 pinMode(redPin, OUTPUT);
 pinMode(greenPin, OUTPUT);
 pinMode(bluePin, OUTPUT);
}


void loop(()
{
 //get a value from the PIR sensor
 pirVal = digitalRead(pirPin);
 //only if the PIR sensor senses movement
 if (pirVal == HIGH) {
   //and if the last time we checked the PIR sensor there was no movement
   if(pirState == LOW)
   { //update the led colors
     // Read the voltage on each analog pin then scale down to 0-255 and inverting the value for common anode
     currentColorValueRed = (255 - map( analogRead(redPotPin), 0, 1024, 0, 255 ) );
     currentColorValueBlue = (255 - map( analogRead(bluePotPin), 0, 1024, 0, 255 ) );
     currentColorValueGreen = (255 - map( analogRead(greenPotPin), 0, 1024, 0, 255 ) );

     // Write the color to each pin using PWM and the value gathered above
     analogWrite(redPin, currentColorValueRed);
     analogWrite(bluePin, currentColorValueBlue);
     analogWrite(greenPin, currentColorValueGreen);
   }
 }
 pirState = pirVal;
}