PIC Powered Metal Detector

[SeanG_65]

Just as a matter of interest, what performance are you getting, ie detection range, discrimination etc?

[Wimax]

I carried out several tests under 'controlled' conditions trying to reproduce, as far as possible, scanning speeds compatible with those of the design at distances between 15 and 10 cm from the coil, sometimes even further, but no more than 20 cm in these favorable conditions, but using standard sensitivity setting (default setting).
I tried with several objects: kitchen cutlery, mobile phone, coins, small and "big" aluminium foil, aluminium water bottles, a few small gold objects (not many, unfortunately for me ) etc.
By obtaining engineering data from the detector, i.e. signal strength and phase shift, I always found that there was a sign difference in the estimated phase shift for ferrous and non-ferrous objects. For the two previous classes I started to sketch out a categorisation criterion by discretizing the detected phase shift by refining the firmware from time to time, but it is a painstaking process.
Unfortunately, I have only carried out one test in a marine environment (on dry sand) with only an aluminium target (a sphere of about 3 cm in diameter), hiding it at a depth of about 5 cm, and managed to detect it correctly.
I confess that the scarcity of field tests is mainly due to the availability of spaces at a reasonable distance and with favourable boundary conditions (not least the constant presence of onlookers) in which to experiment, I would have really needed a garden.

Volunteers are sought for a serious experimentation and project improvement !.

[SeanG_65]

You could have a look at this; https://www.geotech1.com/forums/forum/technology/schematics/414267-sable-vlf-detector-with-vdi-inspired-by-the-raptor-project

or this



or this

https://www.geotech1.com/forums/filedata/fetch?id=359536

[SeanG_65]

https://www.geotech1.com/forums/filedata/fetch?id=371096&d=1674425888

[Wimax]

Thank you very much, I will try as soon as possible, the site requires a registration, but some e-mail domains need a manual procedure being spamming sources.

[Wimax]

I took a look at the schematics and also found a firmware source, definitely very interesting and good projects. However, I am still looking for evidence of experimental studies for target discrimination and cataloging with a scientific approach. On the other hand, I realize that even detector manufacturers do not make public the results of their researches and detailed operating principles, and even in patents they write the essentials, but not everything.

[top204]

That looks like an excellent project Wimax, and you have gone way over my head with the details of phase shifts etc... :-)

If you need faster everything, use the dsPIC33xxCK devices, even if you are not using their DSP, because they operate up to 200MHz, and I'm sure their ADC can read multiple channels at the same time.

[Wimax]

Thank you very much Les! I think you noticed my totally cluttered programming style . I have seen the CK series and it is really interesting, but I would have to buy a suitable development board as well as study the datasheet in depth. I should do quite the same with the EP series, but I can use an eval board I already have... difficult decision really.
However, in my own small way, I am increasingly amazed by the magnificent performance of Positron16, I have also realised other small projects and all thanks to this magnificent compiler and the wonderful work done by its creator!

[top204]

Many thanks for your kind words Wimax. They mean a lot to me. :-)

The 28-pin CK devices may actually be drop in replacements for the 28-pin E type devices. There are some very small pin changes in the PIC24 and dsPIC33 devices, but they follow the rules of 8-bit PIC devices as much as they can and are mostly pin compatable.

When I first created the compiler's code for the dsPIC33xxCK devices and powered one up and got it to work at 200MHz, thanks to the users on this forum who spotted a microchip anomaly with their fuse settings that stopped the high speed working, I was amazed at how fast they can go! And with the compiler's code optimisations, they are incredibly fast, and mostly have to be slowed down. :-)

[John Lawton]

Yes, it's rather a shame they juggled around the /MCLR and power pins though

I've concluded that although it may well be possible to make a general purpose board, IMHO it would have just too many awkward links to make it useable.

So, shortly I'm hoping to announce the two new Amicus16 dev boards, model A for the dsPIC33EPXXXGP502 compatible types and model B for the dsPIC33CHXXXMP502 and similar CK types.

Maybe I should do the model B first for those speed fans...?

John

[SeanG_65]

I've a friend who codes PIC assembly. I showed him some code the compiler produced, he said he couldn't do better.

[Wimax]

Yes, it's rather a shame they juggled around the /MCLR and power pins though

I've concluded that although it may well be possible to make a general purpose board, IMHO it would have just too many awkward links to make it useable.

At the moment I have found it quite smooth, at least at the hardware level, to switch from the Pic24FJ series to the Pic24HJ. I don't know if pin-to-pin compatibility is common to all FJs, but that was the case with the micro I used in the metal detector. Obviously nothing is free, although I benefited from pin-to-pin compatibility ( no small feat once a hardware design is completed) I spent sleepless nights struggling with the DMA !
From your comments about the DsPic33CKs I'm seriously thinking to try the quantum leap !😀