Metal Detector Module

The Metal Detector Module is a basic but complete metal detector.  Just add power and start finding treasure in your couch seat cushions.

FEATURES :

• Built-in PCB trace detector coil
• Buzzer detection alert
• Sensitivity adjustment
• 3 to 5V operation

Virtually all metal detectors work on the same basic principle of using an oscillator that incorporates an inductor(s) as part of an oscillation circuit.  That inductor is composed of wire windings in the sensor head (or in this case, it is PCB traces in a spiral pattern).

Any metal that comes into proximity with this inductor causes its electrical characteristics to change.  That change affects the oscillator frequency or amplitude and that is what alerts us via a buzzer or some other user interface as to the presence of a metallic object.

This module implements a Colpitts oscillator using Q1, some of the capacitors and resistors and the 2 inductors (there is one on top of the board and one on bottom of board).  The oscillator runs at around 300kHz.  When metal comes near, the output transistors Q2 and then Q3 are biased on which results in the buzzer sounding.

The module includes a potentiometer R3 that allows for adjustment of the sensitivity.  If the sensitivity is set too high, the buzzer will sound continuously.  Turning the pot CCW just until the buzzer stops sounding when no metal is present will set the detector for maximum sensitivity.

There are 4 screw holes that can be used for mounting a handle of some type if desired.

Module Connections

To power the module, connect 3 to 5V to the ‘V+‘ break-out point and Ground to the ‘V-‘ break-out point.  This will typically require soldering wires to these two points.

TECHNICAL SPECIFICATIONS