Arduino Light Seeker





Introduction: Arduino Light Seeker

First of all, I'm from Switzerland so please excuse my english mistakes.

Here is one of my first little project I did with my Arduino Uno.

It's is just a little light seeker. The servo turns towards the light.

I made a video to show you what it does :

Step 1: The Wiring

Here is the exact wiring I used.

The only difference is that I fixed the photoresistors on the servo (but I couldn't do it with the program)

Also I used a 9V battery in the video, it was plugged in Vin and GND.

The resistors are 200 Ohm for the LED's and 10 KOhm for the photoresistors.

Step 2: The Code

This is my first code. I tried to translate the comments in english.

The Arduino calculate the difference between the left and right photoresistor and turns the servo if the difference is greater than 30.
When the servo is turning clockwise, the right LED lights up. When it turns counter clockwise, the left LED lights up

If you see any errors or weird thing, please tell me :)

Servo servo; //define servo
int photoD = 0;  //define pin 0 for right photoresistor
int photoG = 1;  //define pin 1 for left photoresistor
int ledD = 3;    //define pin 3 for right LED
int ledG = 5;    //define pin 5 for left LED
int incr = 5;     //value to add to the angle
int valS;          //angle
long temps;      //Time
long temps2;     //Time 2
long temps3;     //Time 3   
long temps4;     //Time 4


void setup()
  pinMode(3, OUTPUT);  //define output pin 3
  pinMode(5, OUTPUT);  //define output pint 5
  servo.attach(8);             //servo on pin 8
  Serial.begin(9600);     //Start serial communcation 
  temps = millis();  
  servo.write(75);            //Initial position for the servo

void loop()
  int valG;        //photoG value
  int valD;        //photoD value

  valD = analogRead(photoD);
  valG = analogRead(photoG);
  //Displays the values on the monitor every second
  if (temps + 1000 < millis()){   
  Serial.print("right photoresistor value :");
  Serial.print("left photoresistor value :");
  Serial.print("Angle :");
  temps = millis();
  if (temps3 + 1000 < millis() && (valD - valG > 20) && (valS < 180)){   
  Serial.println("Turning counter clockwise");
  temps3 = millis();
  if (temps4 + 1000 < millis() && (valG - valD > 20)&& (valS > 0)){   
  Serial.println("Turning clockwise");
  temps4 = millis();
  if (valD - valG > 30) {
       valS = valS + incr;
  if (valG - valD > 30) {
       valS = valS - incr;
  if (valS > 0 || valS < 180) {
        servo.write(valS);                //turns the servo
  if (valS <= 0) {
        valS = 0;
  if (valS >= 180) {
        valS = 180;
  if (temps2 + 500 < millis() && valD - valG < 30 && valG - valD < 30 ){
    temps2 = millis();

Step 3: The End

And... that's all !

I hope you enjoyed this project !

If you have any questions, feel free to ask.



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    Hi, I like your project because your project is cool but simple at the same time! It would be fun to work on this project! Could you give me your contact details so that I could ask more question on it?
    I would like to know what kind of photoresistors did you use and how did you hook up the photoresistor to the servo so that it'll spin acccording to the light detected by the it.