Basic Electronics for Beginners: Arduino Vibration Sensor: SW-420

1. Introduction

Security is an important aspect in homes, lockers, vehicles, and industries. In this project, we design a Vibration Sensor Alarm System using Arduino that detects shocks or vibrations and triggers an alarm using a buzzer.

This system is useful for:

Locker and cupboard security
Bike or vehicle protection
Basic earthquake or vibration detection
Industrial safety monitoring

2. Components

Arduino UNO / Nano
Vibration Sensor Module (SW-420)
Buzzer
LED (optional)
Resistor (220Ω for LED)
Connecting wires
Breadboard

3. Circuit and Connections

Pinout Diagram of Arduino Uno

Vibration Sensor (SW-420): Pinout Diagram

Pinout Diagram of Buzzer

🔌 Vibration Sensor (SW-420):

VCC → 5V
GND → GND
DO → Digital Pin 2

🔔 Buzzer:

Positive → Pin 8
Negative → GND

💡 LED (Optional):

Anode → Pin 7 (through resistor)
Cathode → GND

4. Detailed Step By Step Circuit Working

The SW-420 vibration sensor detects movement or shock:

Inside the module, a spring and mass system responds to vibration
When vibration occurs, the internal contact changes
The module outputs a digital HIGH signal
Arduino reads this signal
Buzzer and LED are activated

👉 No vibration → LOW
👉 Vibration → HIGH

5. Libraries to be included

👉 No external libraries required (simple digital input)

6. Code


#define sensorPin 2
#define buzzerPin 8
#define ledPin 7

void setup() {
  pinMode(sensorPin, INPUT);
  pinMode(buzzerPin, OUTPUT);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  int sensorValue = digitalRead(sensorPin);

  if (sensorValue == HIGH) {
    digitalWrite(buzzerPin, HIGH);
    digitalWrite(ledPin, HIGH);
  } else {
    digitalWrite(buzzerPin, LOW);
    digitalWrite(ledPin, LOW);
  }
}

7. Detailed Step By Step Code Working

sensorPin reads vibration signal
If vibration detected (HIGH):
- Buzzer ON
- LED ON
If no vibration:
- Buzzer OFF
- LED OFF

👉 Simple real-time detection system

8. Working Principle

The SW-420 works on a mechanical vibration detection principle:

Internal spring moves during vibration
Contact is made/broken
Digital signal generated
Arduino processes and triggers output

9. Advantages

Simple and low-cost system
Easy to build and understand
Useful for security applications
Fast response time

10. Disadvantages

May give false triggers (high sensitivity)
Not suitable for precise measurement
Requires adjustment using onboard potentiometer

11. Applications

Anti-theft alarm systems
Locker and safe security
Vehicle vibration detection
Industrial machine monitoring

12. Conclusion

This Arduino Vibration Sensor Alarm System is a simple yet effective security solution. It demonstrates how vibration can be detected and used to trigger alerts in real time. The project can be further enhanced with IoT and GSM features.

Arduino Vibration Sensor: SW-420