A very simple metal detector can be assembled with just two transistors. Such a device is quite suitable for quickly searching for metal objects at shallow depths. The entire circuit together with the coil can be assembled in just 30 minutes.
Will need
In order to make a metal detector you will need the following parts:- Two BC547 transistors;
- Capacitors 103 pF, 22 pF, 103 pF;
- Resistor 2.2 kOhm;
- Variable resistor 50 kOhm;
- Wire 0.3 mm;
- Buzzer.
Scheme and operation
The first transistor houses a high-frequency pulse generator. The maximum generation mode is adjusted using a variable resistor. As soon as metal appears in the coil's visibility, the generator will malfunction and stop oscillating. All transistors will open one by one and power will flow to the buzzer, resulting in a squeaking sound. After removing the metal from the coil, generation will resume.
Making a metal detector
The entire circuit will be assembled without a board by surface mounting. We clamp one transistor in the “third hand” for convenience.
Solder the emitter of one transistor to the base of the other.
Solder the capacitors according to the diagram, a resistor, a variable resistor.
We solder the buzzer and capacitor.
Let's make a coil. We take any frame with a diameter of 5-7 cm and on it we wind windings of 20 turns + 20 turns or only 40 turns with a tap from the middle.
Solder the coil to the circuit.
We solder the power supply from the crown.
The circuit is ready for use.
We serve food. Using a trimmer resistor, we set the limit at which the buzzer sound will disappear. Now if you bring a metal object, the generator will stop and the buzzer will beep.
In the future, the diameter of the coil can be significantly increased, thereby increasing the sensitivity of the metal detector.
