New version (Beta):
In this version this metal detector works with a smartphone or without a smartphone with the possibility of adding an LCD screen. Now Spirit Pi is more stable and reaches more depth. The diagram and the PCB can be found below, also in the file you will download will be gerber file in case someone wants to order the PCB on the JLCPCB page. JLCPCB is a page where we can order the PCBs we want for a very low price, we just have to upload gerber file of the circuit and that’s it.
Now in this detector we have 3 buttons: “+”, “-“, and the “M” menu. With these buttons we can adjust the pulse width, sensitivity and frequency. Instead of the TL072 amplifiers we will use NE5532. The micro controller will use an Arduino nano. The coil is still 25 turns with 0.5 mm wire and the radius 20 cm.
The components I usually buy on Aliexpress for the low price. In this way we can make a good metal detector and spend little money. Below I will leave the links where you can buy these components to make this metal detector!