Arduino Force Sensor Anti-Theft Alarm System

Introduction

Security is a growing concern in both personal and commercial spaces. Traditional security systems can be expensive and complex to install. However, with DIY electronics, you can create a cost-effective, efficient, and customizable anti-theft alarm system using Arduino and a force sensor.

In this guide, we will walk you through creating an Arduino-based anti-theft alarm system using a force-sensitive resistor (FSR). This project is perfect for securing valuable items, safes, or even doors.

Understanding Force Sensors

What is a Force Sensor?

A force sensor, also known as a force-sensitive resistor (FSR), is a component that changes its resistance based on applied pressure. When pressure is exerted, the resistance decreases, allowing us to measure force levels.

Types of Force Sensors

There are various force sensors used in different applications:

FSR Sensors – Used in touch-sensitive applications and security systems.
Load Cells – Used in industrial applications to measure weight.
Strain Gauges – Used in engineering and aerospace applications.

How Does an FSR Work?

A force-sensitive resistor operates on the principle that resistance decreases as force increases. It is commonly used in pressure-sensitive applications such as touch interfaces, medical devices, and security systems.

Components Required

To build this project, you will need:

Arduino Uno/Nano – Microcontroller to process sensor data
Force Sensor (FSR) – Detects force applied to an object
Buzzer – Sounds the alarm upon unauthorized access
LEDs (Red & Green) – Indicator lights for system status
16×2 LCD Display (I2C) – Displays system messages
Push Button – Used to reset the alarm
Resistors (100Ω, 10kΩ) – Required for circuit stability
Breadboard & Jumper Wires – For making secure connections
9V Battery & Clip – Power supply for the system

Circuit Design & Connections

Conceptual Design

The system works by monitoring force applied to an object. When the pressure exceeds a defined threshold, the alarm is triggered. The buzzer will sound, and an LED will light up to indicate unauthorized access.

Arduino Force Sensor Anti Theft Alarm System

Circuit Diagram & Setup

Connecting the Force Sensor
- Connect one terminal of the FSR to 5V and the other to an analog pin.
Buzzer & LEDs
- Connect the buzzer to a digital pin for activation.
- Use a red LED to indicate an alert and a green LED for normal status.
LCD Display
- Connect the LCD via I2C to display messages such as “System Armed” and “Intrusion Detected.”

Programming the Arduino

Required Libraries

Before coding, install the following libraries in the Arduino IDE:

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

Code Overview

Read force sensor values.
If force exceeds a certain threshold, activate the buzzer.
Display status messages on the LCD.
Reset system using a button press.

Sample Code

#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x3F, 16, 2); // LCD HEX address 0x3F -- change according to yours
 
int Force_VAL = 0;
int temp = 0;
int btn = 0;
int buzz = 6;
void setup()
{
  pinMode(A0, INPUT);
  pinMode(4, INPUT);
  pinMode(buzz, OUTPUT);
  Serial.begin(9600);
  lcd.begin();
  
  lcd.setCursor(0,0);
  lcd.print("Force Sensor");
  pinMode(10, OUTPUT);
  digitalWrite(10, LOW);
  digitalWrite(buzz, LOW);

 
}

void loop()
{
  Force_VAL = analogRead(A0);
  btn = digitalRead(4);
  Serial.println(btn);
  lcd.setCursor(0,1);
  lcd.print("Value:");
  lcd.setCursor(7,1);
  lcd.print(Force_VAL);

 if ((Force_VAL < 550) || (Force_VAL > 650))  //Enter Force Value Range
 {
    temp=1;
  } 

 if (btn == 1)
 {
    temp=0;
  } 

 if (temp == 1)
 {
    digitalWrite(10, HIGH);
    digitalWrite(buzz, HIGH);
  }

 if (temp == 0)
 {
    digitalWrite(10, LOW);
    digitalWrite(buzz, LOW);
  }
  
  delay(10);
}

Testing & Calibration

Calibrating the Force Sensor

Adjust the threshold value based on your application.
Test the system by applying different force levels.

Common Issues & Solutions

False Alarms – Adjust sensitivity by modifying resistance values.
Buzzer Not Activating – Check circuit connections and code logic.
LCD Not Displaying Data – Ensure correct I2C address is used.

Enhancements & Features

Adding GSM Module – Send SMS alerts when intrusion is detected.
Wi-Fi Connectivity – Integrate with IoT platforms for remote monitoring.
Multiple Sensors – Use multiple FSRs for enhanced coverage.

Safety & Security Considerations

Ensure the system is well-enclosed to prevent tampering.
Regularly test components to avoid failures.
Follow local security regulations when implementing alarm systems.

FAQs

How sensitive is the force sensor?

The sensitivity varies depending on the model. You can adjust it by modifying the resistance values in the circuit.

Can I use a different Arduino board?

Yes, Arduino Uno, Nano, and Mega all work with this project.

How do I prevent false alarms?

Ensure the force sensor is properly calibrated and positioned correctly.

Can I add a wireless module?

Yes, you can integrate an ESP8266 or Bluetooth module for remote access.

Conclusion

Building an Arduino-based anti-theft alarm system with a force sensor is an excellent DIY security project. This system is simple to implement, highly customizable, and cost-effective. By fine-tuning the settings, integrating additional modules, and expanding functionality, you can create a highly robust security solution.