a_guadalupi • Posted by Arduino_Scuola

Published July 8, 2016 © CC BY-NC-SA

A Simple Light Follower

This lesson aims to show how to make a simple light follower made of cardboard using a microservo.

IntermediateFull instructions provided40 minutes13,323

Things used in this project

Hardware components

Arduino UNO

mini breadboard - mixed colours

10 jumper wires 200mm male

5 LDR

10 10k 1/4w resistor

Analog 180° Micro Servo

4mm cardboard

Software apps and online services

Arduino IDE

Story

1. How does it Work?

The choice to go up or down in order to follow the light is done in a very simple way. There are four LDR two up and two down. Arduino reads the analog value of all LDR, if the average of the two upper values is greater than the two lower the light is up so the angle of the microservo is incremented otherwise decremented.

2. A Little Clarification

Since the average is not a fixed number, as you can see in the code, a threshold is used. In this way the angle is changed if and only if the two averages are widely different.

const int threshold = 50;
[.....]
down_average = (A0_val + A1_val)/2;
  up_average = (A2_val + A3_val)/2;
  diff = abs(up_average-down_average);
  if ((up_average > down_average) && (diff > threshold))
    {
     if (val < 180) //if different from max val
       {
       val++;
       myservo.write(val);
       }
    }
  if((down_average > up_average) && (diff > threshold))
    {
    if (val > 0) //if different from min val
      {
      val--;
      myservo.write(val);
      }
    }

3. The Circuit

Make the circuit below!

4. Print & Cut

Download the attached file, print it, glue it on the cardboard and cut all the pieces for yours light follower. You should obtain something like this.

5. Mount the Base

Mount the breadboard base in this way. Glue it if necessary.

6. Mount the Servo

Mount the servo like below. Screw it for more stability.

7. Mount the Bracket

Mount the bracket in this way.

8. Mount the Servo Gear

Mount the servo gear. Screw it in this way.

9. Put all Together

Put all together. You should obtain something like this

10. Glue the Breadboard on the Base

Glue the breadboard on the base. You can use the biadhesive tape of the breadboard.

11. Screw Arduino

Screw Arduino on the back of the base.

12. Well Done

Well done. Now you have all the necessary. Download the code on your Arduino and enjoy with your light follower!

Schematics

Code

Light Follower code

/*
A simple light follower
 
author: Arturo Guadalupi <a.guadalupi@arduino.cc>
 */
#include <Servo.h>
Servo myservo;
int up_average;
int down_average;
int A0_val;
int A1_val;
int A2_val;
int A3_val;
int val = 90;
int diff;
const int threshold = 50;
void setup() {
  pinMode(A0, INPUT); 
  pinMode(A1, INPUT);
  pinMode(A2, INPUT);
  pinMode(A3, INPUT);
  myservo.attach(11);
  myservo.write(val);
}
void loop() {
  A0_val = analogRead(A0); //reading data from sensors
  A1_val = analogRead(A1); 
  A2_val = analogRead(A2);
  A3_val = analogRead(A3);
  
  down_average = (A0_val + A1_val)/2; //the sum of the two lower sensors /2
  up_average = (A2_val + A3_val)/2;	  //the sum of the two upper sensors /2
  diff = abs(up_average-down_average); //checking the difference between the two averages
  if ((up_average > down_average) && (diff > threshold))
    {
     if (val < 180) //if different from max val
       {
       val++;
       myservo.write(val);
       }
    }
  if((down_average > up_average) && (diff > threshold))
    {
    if (val > 0) //if different from min val
      {
      val--;
      myservo.write(val);
      }
    }
  delay(25);
}

Credits

a_guadalupi

Posted by

Arduino_Scuola

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A Simple Light Follower