Metal detector based on RP2040

Based on Raspberry Pi Pico board, this metal detector is included in pulse induction metal detectors category, with well known advantages and disadvantages. RPi Pico generate 3,3v amplitude pulses at one of GPIO pins. This pulses are amplified and applied to a MOSFET device that had the searching coil in series with drain. The pulse will produce a magnetic field generated by the searching coil, and becose of eddy currents, the target will produce a very low corresponding voltage at the coil terminals. The mode this signal decay depends of target characteristics ( form, type, material ) and the distance. This is the signal we need to analyze, so it is supressed by two antiparallel diodes and passed to an operational amplifier . After amplification, the analog signal is read by one of analog input of Raspberry Pi Pico board and is analized by the software. This poccess is repeatedly for many times per second.