FoxyPI - Arduino Nano-Based Pulse Metal Detector

BC547

General Purpose Dual Op-Amp

Soldering iron (generic)

Arduino Nano

IRF840

BC557

Hot glue gun (generic)

LM385Z-1.2

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.<h3 >Appearance:</h3><figure><img src=https://projects.arduinocontent.cc/3e346fbf-e55c-49b8-8a0d-c514995b65f2.jpg /><figcaption>FoxyPI</figcaption></figure><figure><img src=https://projects.arduinocontent.cc/d094d6ec-3094-42d5-932a-1783224374d0.jpg /><figcaption>Metal detector disassembled for transportation</figcaption></figure><figure><img src=https://projects.arduinocontent.cc/531ac411-ef27-4ee6-bcf9-387ef85dc750.jpg /><figcaption>The appearance of the electronic unit</figcaption></figure>1 - LCD screen2 - LED3 - piezodynamic4 - control button5 - LCD backlight switch6 - power switch7 - signal strength indication LEDs<h3 >Circuit:</h3><figure><img src=https://projects.arduinocontent.cc/41baa3ec-9aab-4627-b626-3aa7914953a7.png /><figcaption>FoxyPI v3 schematic</figcaption></figure><h3 >Firmware:</h3>version 3.8HEX-file for Arduino Nano 3.0 (version 3.8 from 10/11/2020) - <a href="https://acdc.foxylab.com/sites/default/files/FoxyPIv3_8.ino.eightanaloginputs.hex">FoxyPIv3_8.ino.eightanaloginputs.hex</a>ELF-file for Arduino Nano 3.0 (version 3.8 from 10/11/2020) - <a href="https://acdc.foxylab.com/sites/default/files/FoxyPIv3_8.ino.elf">FoxyPIv3_8.ino.elf </a>What's new:improved display of signal curves in test mode (through earlier reading of preset settings, including contrast)version 3.7HEX-file for Arduino Nano 3.0 (version 3.7 from 07/05/2020) - <a href="https://acdc.foxylab.com/sites/default/files/FoxyPIv3_7.ino.eightanaloginputs.hex">FoxyPIv3_7.ino.eightanaloginputs.hex</a>ELF-file for Arduino Nano 3.0 (version 3.7 from 07/05/2020) - <a href="https://acdc.foxylab.com/sites/default/files/FoxyPIv3_7.ino.elf">FoxyPIv3_7.ino.elf </a>What's new:small code optimization was performed to increase the stability of the metal detector;beep indication for errors ERR 01 and ERR 02 addedversion 3.6HEX-file for Arduino Nano 3.0 (version 3.6 from 06/28/2020) - <a href="https://acdc.foxylab.com/sites/default/files/FoxyPIv3_6.ino.eightanaloginputs.hex">FoxyPIv3_6.ino.eightanaloginputs.hex</a>ELF-file for Arduino Nano 3.0 (version 3.6 from 06/29/2020) - <a href="https://acdc.foxylab.com/sites/default/files/FoxyPIv3_6.ino.elf">FoxyPIv3_6.ino.elf</a> What's new:added the ability to configure the guard interval using the GUARD item of the service menu;added auto-tuning of levels 1 and 2 of the audiovisual indication in static mode;integrated test mode (to activate, after switching on, hold the control button until the graph of the signal curve appears)\t\t\t\tversion 3.5HEX-file for Arduino Nano 3.0 (version 3.5 from 11/11/2019) - <a href="https://acdc.foxylab.com/sites/default/files/FoxyPIv3_5.ino.eightanaloginputs.hex">FoxyPIv3_5.ino.eightanaloginputs.hex</a>ELF-file for Arduino Nano 3.0 (version 3.5 from 11/11/2019) - <a href="https://acdc.foxylab.com/sites/default/files/FoxyPIv3_5.ino.elf">FoxyPIv3_5.ino.el</a>fWhat's new:added the ability to adjust the display contrast using the CONTRAST item in the service menuAn example is small/normal/excessive contrast:<figure><img src=https://projects.arduinocontent.cc/1d29ca77-d116-4b08-b9e7-a17c6bbd590a.jpg /><figcaption> </figcaption></figure>version 3.4HEX-file for Arduino Nano 3.0 (version 3.4 from 09/25/2019) - <a href="https://acdc.foxylab.com/sites/default/files/FoxyPIv3_4.ino.eightanaloginputs.hex">FoxyPIv3_4.ino.eightanaloginputs.hex</a>ELF-file for Arduino Nano 3.0 (version 3.4 from 09/25/2019) - <a href="https://acdc.foxylab.com/sites/default/files/FoxyPIv3_4.ino.elf">FoxyPIv3_4.ino.e</a>lf<h3 >Operating principle</h3><figure><img src=https://projects.arduinocontent.cc/00daece6-c319-4ef2-9590-860fd1de2987.png /><figcaption> </figcaption></figure>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.<h3 >Metal detector operation</h3>The metal detector works in two modes: <ul ><li >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);</li></ul><ul ><li >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</li></ul>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:<figure><img src=https://projects.arduinocontent.cc/74393255-bf02-4883-aab2-990f768426be.png /><figcaption> </figcaption></figure>Using the button-controlled menu, you can configure the device parameters:<figure><img src=https://projects.arduinocontent.cc/a52cb337-9e8c-41b4-bfc5-1bbe1c249b0e.png /><figcaption> </figcaption></figure>L - pulse duration (μs)R - pulse repetition rate (pps)I - integrator coefficientF - filter coefficientS - sound (on / off, ON / OFF)C - display contrast Service menu structure:<figure><img src=https://projects.arduinocontent.cc/5c78b7c6-77f6-4846-a73a-7dea01d74fa8.jpg /><figcaption> </figcaption></figure>The double-pole switch with locking in the neutral position and the digital LED voltmeter allow you to determine the voltage of the uC/power battery in any mode of MD operation:<figure><img src=https://projects.arduinocontent.cc/d4253d9c-7528-4a85-8368-14285a52aec8.jpg /><figcaption> </figcaption></figure>Detailed Description (in Russian): <a href="https://acdc.foxylab.com/node/47">https://acdc.foxylab.com/node/47</a><h3 >Tests</h3>The detection range of targets in the &#34;air&#34; 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)<figure><img src=https://projects.arduinocontent.cc/27373e46-1a9b-41b9-a625-6cbe3802c9d8.jpg /><figcaption> </figcaption></figure>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):<figure><img src=https://projects.arduinocontent.cc/0cd8a85d-5825-40e6-bb7e-6bf422ca2248.jpg /><figcaption> </figcaption></figure>During operation, the device should be located at a distance from working televisions, computers, power transformers, CFLs.<figure><img src=https://projects.arduinocontent.cc/e235ee05-879b-4f6d-9aca-19b57022bb03.jpg /><figcaption>Interference from LCD TV</figcaption></figure>Firmware for testing of FoxyPI v3 (hex-file): <a href="https://acdc.foxylab.com/sites/default/files/FoxyPIv3_TST.ino.eightanaloginputs.hex">https://acdc.foxylab.com/sites/default/files/FoxyPIv3_TST.ino.eightanaloginputs.hex</a>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:<figure><img src=https://projects.arduinocontent.cc/c12c5c96-78db-48de-b5a3-82557e0c24e6.jpg /><figcaption>1 - without target, 2 - with target</figcaption></figure>Check &#34;omnivities&#34; MD to coils - a coil from the demagnetization loop (from old TV) (it works well, although the sensitivity is reduced):<figure><img src=https://projects.arduinocontent.cc/6cf1bd38-69c2-43f9-972b-4d526aef38bb.jpg /><figcaption> </figcaption></figure><h3 >Videos:</h3>Non-motion mode<div class="se-component se-video-container __se__float-none" contenteditable="false" style="width: 100%;"><figure style="width: 100%; height: 56.25%; padding-bottom: 56.25%; margin: 0px;"><iframe frameborder="0" allowfullscreen="" src="https://www.youtube.com/embed/1ulevNWBZ9A" data-proportion="true" data-percentage="100%,56.25%" data-size="100%,56.25%" data-align="none" style="width: 100%; height: 100%;" data-index="0" data-file-size="0" data-origin="100%,56.25%"></iframe><figcaption contenteditable="true"><div>Version 3.3, non-motion mode, "air" test</div></figcaption></figure></div>Motion mode<div class="se-component se-video-container __se__float-none" contenteditable="false" style="width: 100%;"><figure style="width: 100%; height: 56.25%; padding-bottom: 56.25%; margin: 0px;"><iframe frameborder="0" allowfullscreen="" src="https://www.youtube.com/embed/GwRvhjCmOE4" data-proportion="true" data-percentage="100%,56.25%" data-size="100%,56.25%" data-align="none" style="width: 100%; height: 100%;" data-index="0" data-file-size="0" data-origin="100%,56.25%"></iframe><figcaption contenteditable="true"><div>Version 3.3, motion mode, "air" and "underground" tests</div></figcaption></figure></div><div class="se-component se-video-container __se__float-none" contenteditable="false" style="width: 100%;"><figure style="width: 100%; height: 56.25%; padding-bottom: 56.25%; margin: 0px;"><iframe frameborder="0" allowfullscreen="" src="https://www.youtube.com/embed/HzIiA9ws0Ak" data-proportion="true" data-percentage="100%,56.25%" data-size="100%,56.25%" data-align="none" style="width: 100%; height: 100%;" data-index="0" data-file-size="0" data-origin="100%,56.25%"></iframe><figcaption contenteditable="true"><div>Version 3.2, motion mode, "air" test</div></figcaption></figure></div>

Schematic (version 3)

FoxyPI - Arduino Nano-Based Pulse Metal Detector

Pulse induction metal detector, built on the Arduino Nano.