White paper by Bruce Candy of Minelab

[Aziz]

Reading my last post i am thinking, why am i pushing this subject off topic!? The hell, i wanted to point on something here..but what? I forgot!?
Bingo! I know!

What the hell, high Q amps got to do with metal detectors???
But...they do!
Think about this!


P.S.
BTW Jadis 200 is approx $27 000 ....

Peanuts! Isn't it?

Hi ivconic,

the real big challenge is, to develop a metal detector with less money and equipment. Just a very simple detector, that works pretty well.

BTW, I will do this. Only a coil and a laptop! No additional electronics at all. Just the coil and the Laptop. So doing metal detection at the level of ground noise (between -90 .. -110 dB).

Aziz

[Max]

Hi ivconic,

the real big challenge is, to develop a metal detector with less money and equipment. Just a very simple detector, that works pretty well.

BTW, I will do this. Only a coil and a laptop! No additional electronics at all. Just the coil and the Laptop. So doing metal detection at the level of ground noise (between -90 .. -110 dB).

Aziz

Hi,
but this way... you have to carry around the laptop during search... and I think is not so good idea for different reasons.

Also... about expense / costs... which is the cost of a laptop today...?

Sure is less than few years ago... but still in many hundreds of dollars/ eur depending on speed (that's a critical factor if you wanna fast - and you sure want- calculations and floating point math in particular... so very hi number of e.g. megaFLOPS).

Why using a laptop then ? Why instead not focus on some newer , powerful MCU instead ?

Will weight less, will consume less power so will stay ON for longer time with less weight on batteries... so the whole detector will weight less too, will be more compact and more and more reliable and robust respect to laptop stuff that will broke e.g. LCD at each tree or rock etc.

Today you can find easy new MCUs with good perfornances... 1:1 pipeline... 100MIPS or more... all easy, cheap, power saving, state of the art solid state and much less weight than a laptop.

But maybe you wanna use the laptop cause of special reasons... I don't know.

These are just my thoughts...

Kind regards,
Max

[ivconic]

Simple?

"..Just a very simple detector, that works pretty well...."

Simple - based on laptop and software??? It couldn't be more complicated!

But i know what do you mean. You are having more than interesting approach. 100% of job you must rely on software itself. Wish you the very best of luck!
Reason i dont think this would be easy, if not almost impossible is the main question; what preferences you can monitor at ... for example gold ring at 45cm depth? Is there any preference on coil surface? Without influencing on it, with some strong em field...what possible preference you can expect from that ring? Such small items, as that ring or some coin, burried in higher depths, simply can not "disturb" soil surface static at all. Proof would be the fact that you just cant monitor it even with some sensitive magnetometer. But using coil for that task...? I dont know.
Other hand, you can use soundcard output and a proper coil and obtain some sort of "tx". Speaker output used as TX and mic or line input as RX. Than, software must have signal generator facillite to output desired signal via spekr.out to properly designed coil, which will solve problem from my question. Power? It will be very low power, yet strong enough to produce some..so,so useable em field arround coil.
Other side, Mic (boosted) or Line (0dB) input must be "clean" from any hums(usually met at pc's) and certainly can be used as ...again so,so RX. Further signal can be easilly processed with some good designed software.
??? Really???! I think this is almost possible!? Wow?!
Aziz keep on doing that and please inform us here!
Might turn to a splendid idea!


Again, wish you much luck and success!
Regards!

[ivconic]

P.S.
For a start you dont need to design special software for this to be checked. I suggest you tu use SpectraLab in conjuction with some signal generator software...just to check idea...

Again..this is possible. But main problem would be pc's internal hum, especially at lower frequencies! How to solve this?

[Aziz]

Yes, my suggestions is possible, because I use it allready in experimental (software allready coded).
Particularly, the next generation of the high fidelity sound cards, built in laptops (96 kHz at 24 Bit!) gives the reason for my effort.
But I have to develop a new search coil for this: High Q, eddy current sensor, driven with ultra low power (just speaker output of Laptop). I will use a stranded HF wire for the search coil.
The software is able to balance the search coil perfectly. Fractions of phase shift to 0 degree and Amplitude to 0.0 V. Then the search coil is becoming "ultra sensitiv".

With an easy external amplifier (to boost TX signals and amplifying the RX signal), I will probably beat all the VLF MD's on the market.

Aziz

[ivconic]

Sounds very possible!
You gonna push me to buy some second hand laptop to experiment with it!? Again money spending...!?
As i said, SpectraLab and som signal generator soft will be enough for a start.
Yet i remember some resident background noise/hum always appearing on pc's... Maybe some filter will help?

[Aziz]

Sounds very possible!
You gonna push me to buy some second hand laptop to experiment with it!? Again money spending...!?
As i said, SpectraLab and som signal generator soft will be enough for a start.
Yet i remember some resident background noise/hum always appearing on pc's... Maybe some filter will help?

I am using my desktop PC as a laptop detector for development at the moment. A laptop can usually also locate and store your GPS position. So you can make a map, where you allready searched (GPS-mouse needed). It may also store ground signals for prospecting (mineral grounds).

The laptop is generating via software any signal you need. The software can apply to the received signal any FFT-filter (even very sharp cut-off frequency, band-pass, notch-filter, etc.). All the main noise signals are due to natural/environmental noise. The noise of the laptop/PC can be filtered out easyly without hardware. Even on my experimental laptop detector, I have nearby an open desktop PC (much disturbing noise), a high disturbing analog monitor with high magnetic field disturbances, many electronics devices, etc. You can filter all the unwanted signals perfectly out by the software.

For best results, the TX signal must be boosted via HiFi-power amplifier (~0.5-2 W or more). Also the RX signal must be amplified with a very low noise pre-amp. The microphone input signal amplifier of the laptop is not convenient. But it will work anyway well.

So I am gonna to develop the search coil particularly for laptop detectors first. And then continuing the laptop detector software.

Aziz

[Aziz]

Hi,
but this way... you have to carry around the laptop during search... and I think is not so good idea for different reasons.

Also... about expense / costs... which is the cost of a laptop today...?

Sure is less than few years ago... but still in many hundreds of dollars/ eur depending on speed (that's a critical factor if you wanna fast - and you sure want- calculations and floating point math in particular... so very hi number of e.g. megaFLOPS).

Why using a laptop then ? Why instead not focus on some newer , powerful MCU instead ?

Will weight less, will consume less power so will stay ON for longer time with less weight on batteries... so the whole detector will weight less too, will be more compact and more and more reliable and robust respect to laptop stuff that will broke e.g. LCD at each tree or rock etc.

Today you can find easy new MCUs with good perfornances... 1:1 pipeline... 100MIPS or more... all easy, cheap, power saving, state of the art solid state and much less weight than a laptop.

But maybe you wanna use the laptop cause of special reasons... I don't know.

These are just my thoughts...

Kind regards,
Max

Hi Max,

Laptops were beeing slow, big and heavy former. Indeed, I made a DSP-board for this purpose many years ago (2 x 40 MIPS 16-Bit DSP). I have learned much on this topic and spent a lot of money. Today, it is not necessary, developing a MC/DSP board anymore. Laptops getting more and more powerfull and low-power. Also the dimensions and weight getting practical to use. In the next coming years, I expect more powerful and nice laptops.
Only 1 GHz speed is fast enough, to get 60-100 number of calculations per second. The battery live isn't good at the moment but some laptop model are convenient. In the future, there will be more low-power laptops.

The power of laptops are: fast development, cheap developing tools, you can change the search mode, better ground signal rejection, better GUI, update your software easyly, using for other things (internet, WLAN, GPS, etc.). All of you should think about developing MD via software. This is the future.

Aziz

[Steve in MS]

The power of laptops are: fast development, cheap developing tools, you can change the search mode, better ground signal rejection, better GUI, update your software easyly, using for other things (internet, WLAN, GPS, etc.). All of you should think about developing MD via software. This is the future.

Aziz

I think you are right, Aziz. Carl mentioned using software back years ago while he was writing articles for Western and Eastern magazine to have one detector mimic several detector designs at will. Maybe after a usable software has been created then the laptop can be replaced with something smaller but still be able to carry out all the functions necessary.
Hope you have good progress toward your goals.
Regards.

[JC1]

Yea

Yea I think Aziz is probably right as well.

It makes much more sense then trying to

develop/code all the software yourself for

the dsp. And one of these years will have a

computer in a little hand held and this will be

nicer.

[kt315]

my prefer is a bad quality schematic on low quality brown paper.
thanks, Tinkerer.

yours

[mikebg]

Errors in "Candy's Gospel"

Minelab's white paper was named by Bulgarian amateur designers "Candy's Gospel".

[Aziz]

Minelab's white paper was named by Bulgarian amateur designers "Candy's Gospel".

Hi Mike,

on the "Paper", there is a reference to online book about DSP's.
It could be interesting for some people here:
To get all the PDF chapters, click link below
http://www.google.de/search?hl=de&q=...tnG=Suche&meta=

or type on google's edit window:
"site:http://www.dspguide.com filetype: pdf"

[mikebg]

Thanks Aziz,
The book by Steve Smith is quoted as [1] in my posting, not in Candy's Paper. I'm using this excellent book to write a very useful lesson for all users and amateur designers of metal detectors. It is as *.pdf file situated in section "General Electronics" thread "Targets frequency response".
Now I'm writing many exercises for this lesson. One of them, titled "Warum eine IB Sonde soll disbalanced sei?", is important for you. (The exercise will be in English :-).