The operation of metal detectors is based upon the principles of electromagnetic induction. Metal detectors contain one or more inductor coils that are used to interact with metallic elements on the ground. The single-coil detector illustrated below is a simplified version of one used in a real metal detector.
A pulsing current is applied to the coil, which then induces a magnetic field shown in blue. When the magnetic field of the coil moves across metal, such as the coin in this illustration, the field induces electric currents (called eddy currents) in the coin. The eddy currents induce their own magnetic field, shown in red, which generates an opposite current in the coil, which induces a signal indicating the presence of metal.
This project focuses on the adaptation, simulation and construction of a commonly available schematic for a Pulse Induction (PI) metal detector. The background information of the history and uses of metal detectors is presented as well as the design criteria for out particular project. The theory behind how a basic PI metal detector works is examined, along with the basic details of a readily available design for a detector.
A detailed examination of the chosen schematics and the function of each component is examined and explained, as well as explanations for certain choices of component values.
The results of a computer simulation using Pspice are shown, and then the results of the actual construction of a breadboard prototype, along with the problems encountered are examined.
schematic circuit diagram of metal detector project
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