A Maker by the name of Dzl (and son) recently built his very own metal detector using an Atmel-based Arduino.
“Most metal detectors use a search coil that act as part of an oscillator circuit. When metal is put in proximity of the search coil both the frequency of the oscillation changes. Many metal detectors uses another more stable oscillator BFO (beat frequency oscillator) to act as a reference for the frequency of the search coil,” Dzl wrote in a blog post.
“Usually the frequency of the BFO is adjusted to exactly match that of the search coil oscillator when no metal is present near this. The signals from these two oscillators are then fed to a (usually analog) circuit that creates an output proportionally to the difference in frequency of the two. This may be either an audible tone and/or some meter reading.”
However, says Dzl, another device that is quite handy at detecting minute frequency changes is a versatile microcontroller (MCU).
“[So] we decided to swap the BFO approach for a microcontroller and came up with [a] simple circuit. The oscillator circuit feeds a 160kHz signal to pin 5 of the Arduino. The Arduino sketch then measures the frequency of this pin very accurately,” Dzl explained.
“When the ‘NULL SW’ button is held this frequency is stored. Any deviation from this frequency is then represented as a series of ‘geiger counter’ clicks on the piezo. The rate of the clicks increases as metal approaches the coil.”
Dzl says he and his son tried a number of different search coils, discovering that approximately 30 turns of wire around a 15cm. plastic bucket worked quite well.
“All we needed then was to tie it all to a discarded Ikea lamp – and hey-presto off to the beach to find treasures. The metal detector has excellent sensitivity and by changing the SENSITIVITY value in the Arduino sketch you are able to tune it for both small and large objects,” he added.
Want to try building your own metal detector with an Arduino? Check out the source code here.
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This looks great thank you. Could you maybe add a video to demonstrate how it works?
hello , will metal detector work for 30 cm deep in ground ?
This works great! I built the circuit, compiled and uploaded the script and it worked with no tweaking at all! Thanks!
how the ardino works in your circuit ???
To be more specific, is the SIGNAL() function call actually doing anything? It doesn’t appear so. I just want to rule it out and delete it if not. It almost seems like the code is missing some library includes?
i will try
how does on power this? Im new, so if you could explain voltage, and were it is on the schematics, i would appreciate it, thank you.
can u send me this project using ARDUINO UNO BOARD..please …
This has got to be worth a go!! I live near the beach and always wanted a metal detector to play with. Guess I can now build one with a very few cheap components and a bit of scrap material. I might add a headphone amp so that It’s more useable. But it looks very good. I’m woindering if it’s possible to attach it to a bigger coil and get deeper search results.
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