Beachmaster Digital

[MartyJ1963]

Nice, neat and compact job Graham! That'll look cool beneath the cuff! Regards, Marty.

[hamedtaran]

Olly I look forward to seeing your work, I'm sure this circuit and the analog circuit you built will work well.

[Olly]

A little bit of progress

I've put together a little experimental platform for testing and software development.
It's using a 6" 3DSS coil to try and live with the large amounts of EMI/RFI in my area.


So far I've got the basic Pulse Induction system working pretty well with automatic coil speed assessment and sample window placement. (with the 6" 3DSS coil my first sample is at just over 6uSec) and it can detect a 5mm x 5mm piece of coke can foil from about 1.5 inches. A 1 Euro coin can be detected from around 9 inches which is about as expected for such a small coil.

I've also been playing with target signal level indication on the display with a coloured signal level indicator on the right and some large digits which will ultimately show the phase shift but for now also show target signal level.


Finally here is a close-up of the battery pack mounted under the cuff.


Still lots to do, but results so far are promising

[Eddy71]

I've also been playing with target signal level indication on the display

A very clean print filling the surface... What slicer do you use to prepare the model for printing?

[Olly]

A very clean print filling the surface... What slicer do you use to prepare the model for printing?

I use Ultimaker Cura with an Ender 3

[Olly]

Latest Update - Audio Working

I've got the little headphone amplifier connected and working well now with the Pico generating PWM audio and controlling the volume of the amplifier.
Have been experimenting with VCO style audio where the frequency increases with target signal strength and so far the results are pretty good. This also works quite well as a pinpointing function if I turn off the SAT function with the pushbutton built into the encoder.

The frequency upper limit is set at around 6.5kHz as the ears tend to lose sensitivity when it goes too high. (Mine do anyway - probably too many rock concerts in my youth)

Does anyone know what frequency ranges are used on other detectors or what the preferred range is (if any) ?

Regards

[jeep6789]

Can we release all the production materials

[Olly]

Can we release all the production materials

Still very much experimental at the moment so no production materials to release as of yet I'm afraid...

[bbsailor]

Still very much experimental at the moment so no production materials to release as of yet I'm afraid...

Oily,

Look up the Fletcher Munson Curve to see the frequency where normal human hearing is most sensitive. The curve changes based on loudness level. On your stereo you will see a loudness button that boosts the low bass and treble frequencies more at lower listening levels, based on the Fletcher Munson Curve.

Joseph J. Rogowski

[Olly]

Oily,

Look up the Fletcher Munson Curve to see the frequency where normal human hearing is most sensitive. The curve changes based on loudness level. On your stereo you will see a loudness button that boosts the low bass and treble frequencies more at lower listening levels, based on the Fletcher Munson Curve.

Joseph J. Rogowski

Thanks Joseph, I'm actually quite familiar with the Fletcher Munson curves. I guess I was more after peoples thoughts on what constituted a pleasing tonal range to use. I don't have much experience with other metal detectors so was wondering if anyone knew what the established manufacturers were using and whether this could be improved upon.

Kind regards

[Olly]

Software architecture

Although working, my experimental code has gotten into a bit of a spaghetti tangle, so I thought I'd take a bit of time to architect it for a more elegant solution.

The following architecture represents my initial thoughts on what I will be working towards although it may change as I progress with the software design.
beachmaster_software_architecture.pdf

[Olly]

Did some initial field trials this weekend on Llandudno beach in Wales.
The pulse induction section is working very nicely although I mostly found bits of old foil.

I did find quite an interesting little aluminium token though - it was around 6" deep and has a diameter of around 8mm, so much smaller than most coins.
The pinpointing function worked particularly well and I was able to not only detect the exact position accurately but with the VCO type audio and small 6" coil, I was also able to get quite an accurate estimation of target size which was pretty useful as there were loads of very large pieces of iron around.

So far so good - feeling quite positive about it - next step to work on the Induction Balance section and get discrimination going.

[hamedtaran]

Did some initial field trials this weekend on Llandudno beach in Wales.
The pulse induction section is working very nicely although I mostly found bits of old foil.

I did find quite an interesting little aluminium token though - it was around 6" deep and has a diameter of around 8mm, so much smaller than most coins.
The pinpointing function worked particularly well and I was able to not only detect the exact position accurately but with the VCO type audio and small 6" coil, I was also able to get quite an accurate estimation of target size which was pretty useful as there were loads of very large pieces of iron around.

So far so good - feeling quite positive about it - next step to work on the Induction Balance section and get discrimination going.

Thank you for your efforts, I hope you are successful, I have a suggestion, I am building a beachmaster version 1, please modify this circuit so that it can use large coils correctly, increasing pulse width, decreasing frequency, etc

[Olly]

Thank you for your efforts, I hope you are successful, I have a suggestion, I am building a beachmaster version 1, please modify this circuit so that it can use large coils correctly, increasing pulse width, decreasing frequency, etc

I'm sure the suggestions made in post #80 and the further comments up to post #83 of the original 'Beachmaster Files' forum should answer most of your questions on running with longer pulse times. https://www.geotech1.com/forums/show...er-Files/page4

[Olly]

Experimental Code - Pulse Induction

I believe that the basic pulse induction part of the detector is working well enough to realease the experimental code of the system so far.
Please note that this is experimental code only and may still include some bugs which I'll hopefully iron out as I progress.
Discrimination with the Induction Balance receive coil is not supported yet, this is what I'll be working on next.
Also not yet included is any form of slope detection on the Pulse Induction side, I will look into this at a later stage.

beachmaster_code.zip

The 'beachmaster.uf2' file in the 'build' sub-directory is the programming file already compiled and ready to drop into the Raspberry Pi Pico.
If you wish to setup your computer system to compile your own then the source code is ready to do so, you'll just need to follow the guidelines as per the documentation at the following link: -

https://datasheets.raspberrypi.com/p...-with-pico.pdf

Regards