Arduino Project: LDR

Beginner

10 Min

30,59

In this project you use an LDR to switch lights on or off, depending on whether there is more or less light shining.

For this project we will use a LDR. LDR is an abbreviation for light depending resistor. Which means that the resistance depends on the amount of light shining on it. The more light shines on the LDR, the lower the resistance becomes.

We can read a value from the LDR with the Arduino. In this project we attach different values to the LED lights. We do this in such a way that if more light shines on it, more LED lights will light up. We do this with if else logic gates and the analogread function. In the programming section I explain what these functions mean.

Building and Wiring

Now that you have collected all the parts you can start putting the project together. The first thing you do in terms of wiring is connect the 5v of the Arduino to the plus of the breadboard. Then you connect the GND to the minus of the breadboard. Then you place the LED lights in the breadboard. It does not matter which color lights you use. The plus side of the LED light is defined by the longest pin. Place a 220 ohm resistor here. On the other side of the resistor you place a jumper wire. This goes to the I/O pin of the Arduino. The left LED goes to I/O pin 2, the one next to I/O pin 3 and so on. Now connect the minus of the LED light (shortest pin) to the minus of the breadboard. Then connect the LDR. Connect one of its pins to the plus of the breadboard. It does not matter which one this is because you cannot connect an LDR the wrong way around. Once you have done that, take a resistor and make sure it is on the other pin. Then put a jumper wire in the breadboard at the same place as the resistor. Put it in the A0 pin of the Arduino. Finally connect a jumper wire from the other side of the resistor to the minus of the breadboard.

Programming

Once you have connected everything correctly, you can start programming.

The code for this project is quite short. In the code we use the analogread function and if else logic gates .

We use the analogread function to read the value of the analog pin. This is the value of the LDR. Then we use the if else logic gates.
At the moment the value matches (so if is) the light goes on for us. If the value does not match (so else is) the light does not light.

//hier zetten we alle componenten op een pin
int sensor = A0;
int led1 = 2;
int led2 = 3;
int led3 = 4;
int led4 = 5;
int led5 = 6;
int Value = 0;

void setup(){
  //hier zorgen we dat die pinnen een puls geven
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
  pinMode(led4, OUTPUT);
  pinMode(led5, OUTPUT);
}

void loop(){
  //nu zorgen we ervoor dat hij A0 leest
  Value = analogRead(sensor);
  delay(100);
  //nu laten we het lampje aangaan 
  //als de waarde 110 of hoger is
  if(Value >= 110){
    digitalWrite(led1, HIGH);
  }else{
    //anders gaat hij uit
    digitalWrite(led1, LOW);
  }
  if(Value >= 125){
    digitalWrite(led2, HIGH);
  }else{
    digitalWrite(led2, LOW);
  }
  if(Value >= 140){
    digitalWrite(led3, HIGH);
  }else{
    digitalWrite(led3, LOW);
  }
  if(Value >= 155){
    digitalWrite(led4, HIGH);
  }else{
    digitalWrite(led4, LOW);
  }
  if(Value >= 170){
    digitalWrite(led5, HIGH);
  }else{
    digitalWrite(led5, LOW);
  }
}

Arduino Project: LDR

Building and Wiring

Programming

Required products