Metal detector schematic?

 I'm looking for an amazingly simple metal detector schematic, anyone?

Johenix7 years ago
You need as followes:
1. headphones
2. a power supply (a battery)
3. an interupter (a buzzer)
4. 4 germanium diodes arranged in a rectifer bridge
5. Wire enough for two coils, one oval and one in a figure 8 shape
about the same size wound inside the other
 
The headphones are attached to the + & - outputs of the rectifier bridge, the oval coil is attached to the ac inputs of the rectifier bridge.
The battery, buzzer and figure 8 coil are connected in series.
The buzzer pulses the current flowing through the figure 8 coil.
In one hole of the figure 8 coil the magnetic north is up in the other it is down thus it normally does NOT induce a current in the oval coil and cause a tone in the headphones.
When metal is brought near the coil assembly it causes one side of the figure 8 coil to have a stronger (or weaker depending on the metal) magnetic field thus allowing a current to be induced in the oval coil producing a tone in the headphones.
You could build something like this using transistors.