Published June 25, 2022 © LGPL

Very simple alarm using a photoresistor

In this project we are going to make a very simple alarm that uses minimal components.

BeginnerFull instructions provided716

Things used in this project

Hardware components

Photo resistor

Arduino Mega 2560

I use an Arduino Mega 2560 but you can use any other Arduino board as well.

Resistor 10k ohm

Buzzer

Story

In this project we are going to make a very simple alarm that beeps if someone walks by. We are going to use a photoresistor to detect changes in light, which indicate that someone walked by.

Follow the steps as shown in this video.

Code

Code

int buzzer = 11;


void setup(){
 pinMode(buzzer,OUTPUT);
}



void alarm(){
 int i;
 int j = 0;
 while(j < 10){
   //output a frequency
   for(i=0;i<80;i++){
    digitalWrite(buzzer,HIGH);
    delay(1);//wait for 1ms
    digitalWrite(buzzer,LOW);
    delay(1);//wait for 1ms
   }
   
   //output another frequency
   for(i=0;i<100;i++){
      digitalWrite(buzzer,HIGH);
      delay(0.5);
      digitalWrite(buzzer,LOW);
      delay(0.5);
   }

  ++j;
 }
}



void loop(){
  int x = analogRead(A0);
  delay(10);
  
  if(abs(analogRead(A0) - x) > 2){
    alarm();
  }
}

Very simple alarm using a photoresistor

Things used in this project

Hardware components

Story

Schematics

Schematics

Code

Code

Credits

galoebn

Comments

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Very simple alarm using a photoresistor

Very simple alarm using a photoresistor

Things used in this project

Hardware components

Story

Schematics

Schematics

Code

Code

Credits

galoebn

Comments

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