Pi metal detector with discrimination

Description

The metal detector works on 400 hz.
The machine has audio jack.
The battery is 12v -2,2A.
You can work up to 10 hours with fully charged battery.
The machine is sensitive to non-ferrous metals.
size of the square coil is 1x1m(you can order a custom size square coil).
The machine has 5 years warranty on the electronics and 2 on the battery.