Introduction

A Continuity Tester is a simple electronic device used to check whether an electrical path is complete or broken. It helps identify open circuits, faulty wires, broken tracks on PCBs, and defective components.

This project is widely used by electricians, technicians, and electronics students.

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Objective of the Project

The objectives of this project are:

• To detect continuity in electrical circuits.
• To identify open or broken connections.
• To provide audio or visual indication of continuity.
• To understand basic testing and troubleshooting methods.

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Working Principle

The continuity tester works on the principle of current flow detection.

Basic Operation

1. The tester applies a small voltage across the test probes.
2. If the circuit is complete, current flows.
3. This current activates a buzzer or LED.
4. If the circuit is open, no current flows and no indication is given.

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Components Required

Basic Continuity Tester

• Battery (3V–9V)
• Buzzer
• LED (optional)
• Resistor (220Ω – 1kΩ)
• Transistor (BC547)
• Test Probes
• Connecting wires

Arduino-Based Continuity Tester

• Arduino Uno
• Buzzer / LED
• Resistors
• Test probes
• Jumper wires

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Circuit Diagram

Basic Continuity Tester Circuit

Battery + ---- Resistor ---- Probes ---- Transistor ---- Buzzer ---- Battery -

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Arduino-Based Circuit

Probe 1 ---- D2
Probe 2 ---- GND
Buzzer ----- D9

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Arduino Code (Optional)

int probePin = 2;
int buzzerPin = 9;

void setup() {
  pinMode(probePin, INPUT_PULLUP);
  pinMode(buzzerPin, OUTPUT);
}

void loop() {
  if (digitalRead(probePin) == LOW) {
    digitalWrite(buzzerPin, HIGH);
  } else {
    digitalWrite(buzzerPin, LOW);
  }
}

Code Explanation

• Arduino checks continuity between probes.
• If continuity exists, buzzer turns ON.
• Internal pull-up resistor improves stability.

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Advantages

• Simple and easy to use
• Low cost
• Quick fault detection
• Portable

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Applications

• Wire testing
• PCB troubleshooting
• Electrical maintenance
• Electronics repair

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Conclusion

The Continuity Tester is an essential testing tool for electronics and electrical work. This project helps beginners understand fault detection and troubleshooting techniques and serves as a foundation for advanced diagnostic tools.