FoxyPI - motion/non-motion pulse induction metal detector, built on the Arduino Nano 3.0, with audiovisual indication, setting parameters via the menu, automatic or manual ground balancing.
HEX-file for Arduino Nano 3.0 (version 3.4 from 09/25/2019) - https://acdc.foxylab.com/sites/default/files/FoxyPIv3_4.ino.eightanaloginputs.hex
ELF-file for Arduino Nano 3.0 (version 3.4 from 09/25/2019) - https://acdc.foxylab.com/sites/default/files/FoxyPIv3_4.ino.elf
With a sharp decrease in the current in the search coil, its magnetic flux also decreases sharply. This phenomenon causes the occurrence of eddy currents in the target, penetrated by this magnetic flux. The resulting eddy currents counteract the reduction of the magnetic flux, which is manifested in a change in the voltage curve on the coil and is noticed by the device.
The metal detector works in two modes:
- static mode (non-motion mode) (default) - the signal level is taken into account, does not require constant coil movement (can be used both for pinpointing the target location and the main search mode);
- dynamic mode (motion mode) - the dynamics of the signal changes is taken into account, during the search the coil must be moved above the ground surface
When a metal target object is detected, a sound signal of varying tonality sounds and LEDs light up. The signal changes in accordance with the dynamics (in dynamic mode) or the level (in static mode) of the received pulse.
When the detector is turned on, auto-balancing is performed. In the process of auto-balancing, the optimal initial delay and duration of the analyzed signal are estimated, and the dynamics of the signal (in dynamic mode) or signal level (in static mode) is evaluated. Also, balancing can be started/stopped during operation by pressing the control button. After the end of the auto-balancing, a short beep sounds and the “zero” value is displayed:
Using the button-controlled menu, you can configure the device parameters:
L - pulse duration (μs)
R - pulse repetition rate (pps)
I - integrator coefficient
F - filter coefficient
S - sound (on / off, ON / OFF)
The detection range of targets in the "air" test in non-motion (in a motion a little less) mode:
(the test was carried out with the batteries discharged to 1.3 V , therefore, the data are understated)
golden ring (3) - 9 cm;
coin 5 roubles (U.S. quarter analog) (2) - 15 cm;
HDD plate (1) - 33 cm.
Some results of the garden search with FoxyPI (after electrolytic cleaning):
During operation, the device should be located at a distance from working televisions, computers, power transformers, CFLs.
Firmware for testing of FoxyPI v3 (hex-file):
In test mode, the metal detector generates a current pulse with a duration of 150 μs in the search coil after switching on, and then it displays the received signal on the screen. Pressing a button generates a new impulse, etc.
Examples of signals: