Full m/lab SD2000 schematics

Corbyn filed patent GB2071327 29th Nov 1979. Bruce Candy mentioned Corbyn and Poole in his patent, filed early in 1990. It's unclear if he even knew of Eric's work. The internet as we know it now didn't exist and searching patent data bases was time consuming, costly and a nightmare. The only other source of info was in prestige journals. The GS4 was mentioned once in one small article in our G&T magazine but it was never mentioned again.

The idea of identifying a noise and subtracting it has been around since electronics was a pup. The art is in devising the most efficient way to do this. If you succeed and the idea is novel then you can patent it. Candy’s Litz wire patent was granted because of a novel finding even though this wire had been previously used in coils. There are several patents proposing variations of ML's method but most are based on simple relic hunting pi theory and have serious flaws when it comes to dealing with our ground here in Oz. The ML patents aren't just based on multiple pulse lengths. You will be in trouble if you pinch the method proposed for a repetitive single pulse length.


A vlf was sometimes described as a mineral or out-of-balance detector. A pi isn't much different and also responds to minerals. It just doesn't need to cope with the ground X signal and the problems it causes for CW designs such as IB or VLF. In other words, vlf has it's own set of limitations and pi also has it's own, but separate set of limitations which are unlikely to be overcome. Competitors should have researched pi at least ten years ago. I think you will find they have left it too late!!!
Rob.

Sir,
Members of this forum are entitled to know the answer to the following questions:
Are you on the payroll of ML? Yes or no
Do you receive any direct or indirect pecuniary or other benefits from ML? Yes or no

[Esteban]

Last Candy's patent:

http://www.freshpatents.com/Rectangular-wave-transmitting-metal-detector-dt20080228ptan20080048661.php?type=description

Examination of the beast.

I have connected up a logic generator to the SD2000 so I can play with the timings, she is very sensitive to small targets by getting the sample delay around 12us. What I did notice though was the detector was a lot quieter. This makes one think that the 4000 series IC are not as clean cut as they should be. Is that phase jitter I see on the 4013 at pin 13? I have no idea how it would behave in the real World as I am not going detecting with a 45 kilo digital generator on my back..lol

Another thing of extreme interest to me is that by increasing the transmit time and making the ground balance pulse much more narrow the sensitivity goes through the roof, like I mean at least 100% on large objects. I think that the later machines are more sensitive to small Gold by way of removing one of the three GB pulses. There is a lot to be learned by tinkering with the SD2000 circuit, I have a feeling that a better way of ground subtraction could be discovered by using this design as a basic building block.

Now where is that Micro controlled Bulgarian model? They better hurry up as the Snoop factory in China say they could reproduce this detector for $85 USD. (inc coil)

forgot

Hi Aziz,

By the way I forgot to say Carl has most patents here:

http://geotech.thunting.com/cgi-bin/pages/common/index.pl?page=metdet&file=patents.dat

Hi Mark,

I know nothing about that schematic other than it looked like

the patent. Now thats where it gets interesting. You see the hardware

is easy enough to design, IF you can figure out what needs to be done

as far as signal processing in concerned. And that information is contained in

the words of the patents.

US4890064

Hi Aziz,

Here you go !

http://www.google.com/patents?id=7gwyAAAAEBAJ&dq=4890064

Google is great.

Hope everybody bought stock when it was cheap.

Yea Aziz, people think minelab patented Litz wire, which they didn't,

they patented the reduced time constant eddy currents running in the receive

coil wire where the DD coils cross over. And using a small diameter wire for this.

these currents change amplitude as the coil is moved closer and further from the

ground resulting in a maybe detectable signal. I've never done the test.

The small diameter wire causes these to die out before sampling (???)) i guess.

Oh well read the patent, you will understand it.

The place where I found an advantage of Litz wire in PI is for very large monocoils

like >1 meter with 14 to 21 turns and the length of the wire becomes very long

and the Litz is faster. Or so I have observed. It is also heavier, but the sensitivity

increase is worth it. Increased skin results in greater velocity of propagation.

[Aziz]

I am wondering about obtaining the patent for Litz-wired coil. This type of coil were used for many decays before in radio antennas (LW/MW).
Anyway, the patent is dated:
Filing date: Jul 27, 1987
Issue date: Dec 26, 1989
So the patent protection is expired.

[Esteban]

Patents

Visit Google patents, over 7,000,000 patents. You don't need to know the # of patent, you also can type the name of inventor, for example Candy, Bruce. See the pic. Whit this method we found 100 patents, metal detector or not, but is very easy! Also you can download the patent and see appart drawing, etc.

http://www.google.com/patents

Hi JC1,

I remember that schematic, at the time I thought it was just a concept drawing based on those patents? There was never any follow up as I recall.

Bugwhiskers,

Thanks for sharing your educational code!

Regards mark

[bugwhiskers]

Hi Zed,

The fastest the ATTiny can run is 16MHz, that makes a resolution of 62nS and the ATMEGA644 20MHz or 50nS.

regards
bugwhiskers

[ZED]

Hello Bugwhiskers

With your current offerings would i be able to nibble at the pulse widths for the samples,nibbles as in could i increase and decrease the width of the
samples by amounts as small as 10 or 20 nano/sec.
The reason i ask is i would like to see if i could set the demodulators up without the 25 turn trim pots.

Zed

[robby_h]

Corbyn filed patent GB2071327 29th Nov 1979. Bruce Candy mentioned Corbyn and Poole in his patent, filed early in 1990. It's unclear if he even knew of Eric's work. The internet as we know it now didn't exist and searching patent data bases was time consuming, costly and a nightmare. The only other source of info was in prestige journals. The GS4 was mentioned once in one small article in our G&T magazine but it was never mentioned again.

The idea of identifying a noise and subtracting it has been around since electronics was a pup. The art is in devising the most efficient way to do this. If you succeed and the idea is novel then you can patent it. Candy’s Litz wire patent was granted because of a novel finding even though this wire had been previously used in coils. There are several patents proposing variations of ML's method but most are based on simple relic hunting pi theory and have serious flaws when it comes to dealing with our ground here in Oz. The ML patents aren't just based on multiple pulse lengths. You will be in trouble if you pinch the method proposed for a repetitive single pulse length.

A vlf was sometimes described as a mineral or out-of-balance detector. A pi isn't much different and also responds to minerals. It just doesn't need to cope with the ground X signal and the problems it causes for CW designs such as IB or VLF. In other words, vlf has it's own set of limitations and pi also has it's own, but separate set of limitations which are unlikely to be overcome. Competitors should have researched pi at least ten years ago. I think you will find they have left it too late!!!
Rob.

check this schematic

Hi Carl,
Take a look at US patent 5576624, The timing pattern and demodulator is almost identical to the Sd2000.
Also see 5537041, fig 9 show a similar demodulator which combines short, medium and long ground balanced signals, then selects the strongest signal.
Also see 5506506.
These three patents cover the SD's, Gp's, soverign and explorer. In my opinion all three patents are linked and must be considered, when developing new or novel approaches.

Thanks Zed and Carl

Mark

Hi Mark and all,

And when you get through looking at those patents.

Look at this !

https://www.geotech1.com/thuntings/showthread.php?t=11374

No part numbers, no code, but Hmmmmmm...

Looks kinda alike.

Thought the minelab used NE5534 or 5532 on front end

on one kind of detector could be wrong.

Just a humble opinion.

Have to look more and haven't the parts to

build it to test it, but this 2000 front end is not looking

too exciting to me, at the moment.


Hi Carl,

You the Man !!!

and get another gold star on your Man Card.

Remember when Tektronix and HP and other equipment

came with very very well done schematics?

Wonder why they weren't afraid?

Want me to tell you?

No you don't.

JC1

[bugwhiskers]

Code update

The attached has some typo's corrected and following specific requests, info about how to change the timings to get precise values.
It's not the 3000 timings woody but with a few changes could be adapted.

Anybody contemplating the micro-controlling of any PIMD (Delta Pulse, GSIV etc) could use this as a template for their own timings.

regards
bugwhiskers

[Woody.au]

Hey bugwhiskers,

Thats a nice bit of code that you have posted, it sure will come in handy for the guys experimenting.

PS. Looks like GP3000 code to me? As long as its for educational purposes then its ok.

[bugwhiskers]

Educational software.

The attached .txt file may assist those who wish to experiment.
Be sure to rename the extension to .asm before loading into AVR Studio.

regards
bugwhiskers