Android Phone Based Metal Detector - FCMD

[moodz]

I see that you are using the HC-05 Bluetooth module to transfer data to your phone. I think it would be worth trying to use the nrf24l01 for data transfer because it should also be able to communicate with the phone via BLE and its power consumption is lower, I think.

https://www.youtube.com/watch?v=2ZlZVE3XjOw

That is a possibility...but also looking at simultaneous audio and data over BT using BT401 or similar.

[Marchel]

I see that you are using the HC-05 Bluetooth module to transfer data to your phone. I think it would be worth trying to use the nrf24l01 for data transfer because it should also be able to communicate with the phone via BLE and its power consumption is lower, I think.

https://www.youtube.com/watch?v=2ZlZVE3XjOw

[moodz]

The good news .. the ground balance test in the field worked better than expected.
Easily balanced a range of goldfield grounds except beach ( to do ).

The bad news ... trying to video one phone (running the detector app) with another phone and holding the detector on a hot day with severe shading and reflections just did not work.

...So I have changed the app so it can do all the video work.

It records the detector app screen in real time and overlays the front or back cam on the screen.
1 tap toggles the video to full size vs PIP ( picture in picture ).
2 taps toggles the video back / front cam.
The PIP may be dragged to any position on the screen.
The detector app controls are fully functional and will be captured if you are recording.
You can stop or start recording obviously and sound may be captured or muted.
Video is captured as MP4
The default is PIP ( recording off ).

Below is a screen shot from a short video shot just now in the lab ... .... might add timestamp and GPS coordinates ( or not ).

This should make detector videos in the field really easy ... I hope.

[Marchel]

Good work...what is your transmit scheme.

The RX part is based on Minelab coils and the TX circuit is based on the XP Deus 2.

[moodz]

I developed a metal detector development board for these STM32 boards. Here are the latest documents, I have the latest board made at home but I haven't had time to test it yet so I don't know if there are any bugs on the board.

Good work...what is your transmit scheme.

[Aziz]

Here is an engineering presentation on a new detector to management.

https://www.youtube.com/shorts/L2-krroaLqQ

This is great magic.

[ivconic]

Here is an engineering presentation on a new detector to management.

https://www.youtube.com/shorts/L2-krroaLqQ

I am developing a new business strategy that will work in the spirit: WeDontAct-WeStayPut!

[Marchel]

I developed a metal detector development board for these STM32 boards. Here are the latest documents, I have the latest board made at home but I haven't had time to test it yet so I don't know if there are any bugs on the board.

[moodz]

Hi Paul,

your final ENOB of 21 bits on a fast 16-bit ADC is quite good. It is even better than most slow 24-bit ADC's can arrive.
Well, I don't get the same level of performance on my 192 kHz/24 bit sound card. I'm limitted to relative low frequency responses, which limits the total detector sensitivity.

I'm really impressed of your KISS and cheap project. Well done!

Thanks Aziz ...

You dont have to be limited .. these boards are very cheap and all tools are free / open source.

[moodz]

Here is an engineering presentation on a new detector to management.

https://www.youtube.com/shorts/L2-krroaLqQ

[ivconic]

If I were the CEO and Paul my chief development engineer; This is what our daily briefing would look like:
(I hate losing my hair)

[Aziz]

...not quite what I imagined on post #1 .. but here is the android phone based ( connected ) detector ready for field tests !

https://youtu.be/Q2FyQp9yhN4

"SF Detector"
Science-Fiction Detector?

[Aziz]

Hi Paul,

your final ENOB of 21 bits on a fast 16-bit ADC is quite good. It is even better than most slow 24-bit ADC's can arrive.
Well, I don't get the same level of performance on my 192 kHz/24 bit sound card. I'm limitted to relative low frequency responses, which limits the total detector sensitivity.

I'm really impressed of your KISS and cheap project. Well done!

[moodz]

...not quite what I imagined on post #1 .. but here is the android phone based ( connected ) detector ready for field tests !

https://youtu.be/Q2FyQp9yhN4

[moodz]

Here is the final performance spec for the field test unit. This pretty much agrees with the experimental results in the lab regarding sensitivity and noise.
I would expect the noise ( EMI mainly ) to be less in the field.
It also demonstrates that the 16 bit ADC is a good choice ... a 24 bit ADC does not bring significant benefit as it only shifts the noise dominance from the ADC to the frontend.
( remembering that the 16 bit ADC samples much faster than the the 24 bit ADC )