Simple Metal Detector Circuit Using 555 Timer

Welcome to the interesting world of electronics, where creativity and usefulness meet! In this thorough introduction, we set out to explore the complexities involved in building a Metal Detector with the versatile 555 Timer IC. Metal detectors are well known for their many uses in archaeology, security, and recreational activities. It invite us to investigate the relationship between technology and curiosity.

Our project is built around the 555 Timer, reliable integrated circuit that leads us through the concepts of astable and monostable configurations. By diving deeper into this project, we will not only understand how a metal detector works but also learn a great deal about oscillatory circuits and pulse-width modulation.

This project promises to be a comprehensive learning experience, regardless of your level of knowledge with electronics or desire to learn more about the complexities of circuit design. At the conclusion of this challenge, you will possess not only a working metal detector but also an enormous amount of knowledge that goes well beyond this task. So let’s get exploring and use the famous 555 Timer IC to navigate the complex connections of Metal Detector Construction!


Metal Detector Circuit Using 555 Timer

Circuit Schematic

Metal Detector Circuit Using 555 Timer


  • 555 Timer IC
  • 47KΩ Resistor
  • 2.2µF/25V Electrolytic Capacitor
  • 10 uF/25V Electrolytic Capacitor
  • Buzzer
  • 170 Turns of 10 cm Diameter Coil
  • 9V Battery

Circuit Connection

The metal detector circuit’s connections are all shown in the circuit diagram. Here, a square wave frequency is produced by the 555 timer integrated circuit, which also produces pulses at human-audible frequencies. The audible frequency is produced by the 2.2 uF/25V capacitor located between pins 2 and 1.

The circuit consists of an RLC circuit made up of 150 turns of copper coil for the inductor, 47 KΩ resistors, and 2.2 µF/25V capacitors. The primary component of this metal detector is the RLC circuit.

The output audible sound is produced by a small 10 uF/25V capacitor, whose anode part is connected to a small buzzer, and which is connected between the output pin 3 and the RLC circuit junction.

Working Principle of Metal Detector

Since the inductor’s coil in this case is air-cored, a metal object placed close to the coil serves as the inductor’s core. The coil’s inductance then undergoes a significant change. When compared to the metal object, the total reactance or impedance of the RLC circuit changes by a certain amount due to these abrupt changes in the coil’s inductance.

Initially, in the absence of any metal objects, the device’s signal produces an audible sound. The signal sent to the buzzer will now differ from the first one due to the reactance change surrounding the RLC circuit.

As a result, when a metal object is placed close to the coil, the RLC circuit’s impedance varies, and concurrently, the buzzer’s signal varies.

Application of Metal Detector

  • Security Systems: Security systems make extensive use of metal detectors to find metal objects that people are carrying. In public gatherings, airports, and high-security locations, it is essential.
  • Archaeology and Treasure Hunting: Metal detectors are used by treasure seekers and archaeologists to find valuable objects or buried artefacts. The metal detector with 555 Timer offers hobbyists in these domains an affordable option.
  • Hobbyist and Educational Projects: A metal detector that uses a 555 Timer is a great option for educational and hobbyist projects due to its simplicity and effectiveness. It functions as a practical tool for teaching fundamental sensor technology and electronic circuits.
  • Search and Rescue Operations: In search and rescue operations, metal detectors are used to find metallic objects in a variety of options, including weapons and tools. Emergency response teams and law enforcement benefit from this.
  • Underwater Exploration: Underwater metal detectors are modified metal detectors that are used to find metallic objects that are submerged. Underwater construction projects and marine archaeology will benefit from this.

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