A very simple metal detector electronic project can be designed using a simple 555 timer integrated circuit . As you can see in the schematic circuit , this electronic project requires few external electronic parts .
This circuit detects metal and also magnets. When a magnet is brought close to the 10mH choke, the output frequency changes.
This metal detector project can be powered from a power supply that can provide an output DC voltage between 6 an 12 volt .
If a metal is closer to the L1 coil , will produce a change of output oscillation frequency, that will generate a sound in the 8 ohms speaker .