Universal PI Micro

[danny475bek]

hi

Hi to all

This links is my projects viedos.

http://video.google.com/videoplay?do...28985205264269

http://video.google.com/videoplay?do...07037523843742

@bugwhiskers

Thank you for explanation.

hi
can you pleas publis your project step by step in order to make it usefull to us
i will be thankfull

[Tinkerer]

The current mirror (LM394) at the front end of the SD2000 perhaps does the same thing?

Thanks for the many interesting links and information. It will take me some time to look at all that.

The "Pinguino" sounds interesting.

If we can combine intrinsic metal detector knowledge, with digital programming, we will end up with something very useful.

Team work can get us there.

Tinkerer

[matabele]

SD2000 front end

The current mirror (LM394) at the front end of the SD2000 perhaps does the same thing?

[matabele]

Preamplifier

Looking through some reference material, it would appear that the response from your receiver coil resembles the voltage response shown for the loop on this link:http://www.vlf.it/minimal2/minimal2.html

The article explains why a preamp functioning as a current to voltage amplifier is better in these circumstances than a voltage amplifier. Some additional theory can be found here

A realisation of this circuit using an OP27 is here and one based upon an LT1028 is here.

It may also be possible to build a satisfactory (and cheaper) current to voltage input preamp utilising an OPA134 or perhaps even a NE5532.

[matabele]

Time Domain Detector

Until recently, it was not possible to build a time domain instrument at reasonable cost, as this requires a dynamic range exceeding 100dB. Most multichannel instruments, therefore, resorted to multi discreet channel or swept frequency techniques in the frequency domain.

I believe that it is now possible to build a quality time domain instrument with off the shelf components - however, many difficulties must be overcome. For example your current IB instrument does not appear to receive a classic time domain response (which should resemble an exponential decay curve.)

There are several problems to be addressed in order to increase the bandwidth (dynamic range.) Early stage sampling corresponds to higher frequencies, late stage sampling to lower frequency:
Using a digitiser for TD measurements

For small shallow targets we require fast switch off for early stage sampling, and for larger deeper targets we need better resolution in the late stage. This requires work on a broad band receiver loop, with low noise preamp, something the ELF community have been doing for some time.

To 'tune' the response it is also possible to transmit a wave rich in the frequencies of interest rather than a square wave. There are two approaches to this:
- either use a FPGA to create an arbitrary waveform generator - something like this
- or (my preference) - to use a PWM to create the desired wave somewhat in the fashion of magic sinewaves. A couple more links about how to do this yourself.

http://en.wikipedia.org/wiki/User:Kieff/Sine_from_square_waves
http://massmind.org/techref/io/pwm/harmonic.htm

Finally, we need to work on the uC. My preference is to piggyback on the robotics community, and use either an Arduino, or my preference the Pinguino. This will cut down development time, and enable additional tinkerers to get involved!

Hope the links stimulate some ideas.

[Tinkerer]

Yep - live not too far from there, where the 'goway' birds cry.

PI metal detectors generally record 3 channels - each corresponding to an integral of the response over a certain period (channel) after different delays. One is generally a ground balance - the other two are on either side of the 'knee' in the response signal.

The problem is that ground and target responses are highly variable - the trick is to 'tune' the instrument to separate the target response from the ground signal in the presence of noise for the particular conditions encountered. This can not be done in the general case, as conditions vary tremendously (hence the 'salt', 'deep' etc. settings on many instruments.)

An instrument which records the entire decay curve could be customised by the user to match the specific conditions encountered - the whole response being compared to a ground response for the particular location and coil used.

With the TINKERERS_V1, I have been using 4 different samples, placed at strategic points in time.

http://www.geotech1.com/forums/forumdisplay.php?f=53

This is working well and gives good discrimination.

I would like to improve on that method and extract 10 or even 20 samples in quick succession to capture a whole time section.
The reason for this can be better explained when you look at the pictures at:

http://www.geotech1.com/forums/showthread.php?t=15441

Where I try to show that there is a lot of information available, if one knows where to look for it.
When locking at the oscilloscope screen, I can see movement at certain spots in time that indicate the TC of the target and if it is iron or non magnetic metal. Sampling at these spots let's me extract this information.

This information has thought me how to produce a TX pulse of a different shape, that gives more information about the target, because it excites core eddy currents not only skin effect eddy currents.

I believe that if this is taken a step further, like you indicate, recording a significant section of the decay curve, much more information can be extracted and much better compensation for mineralized ground and other PI problems could be designed.

Unfortunately, I am not capable of doing the programming. Are you?

Tinkerer

[matabele]

Intabazinduna

Yep - live not too far from there, where the 'goway' birds cry.

PI metal detectors generally record 3 channels - each corresponding to an integral of the response over a certain period (channel) after different delays. One is generally a ground balance - the other two are on either side of the 'knee' in the response signal.

The problem is that ground and target responses are highly variable - the trick is to 'tune' the instrument to separate the target response from the ground signal in the presence of noise for the particular conditions encountered. This can not be done in the general case, as conditions vary tremendously (hence the 'salt', 'deep' etc. settings on many instruments.)

An instrument which records the entire decay curve could be customised by the user to match the specific conditions encountered - the whole response being compared to a ground response for the particular location and coil used.

[greylourie]

multi-channel recording entire decay ?

Thanks.

I have some ideas for a multichannel receiver of this type, which records the entire decay rather than just a few fixed channels.

Are there any other active projects of this nature?

Hi Matabele.

Would you care to elaborate ? When you say multi-channel receiver, my mind goes blank. I'm not really knowledgable about any of this.

BTW, have you ever been to Intabas Induna ?

[matabele]

Links

Thanks.

I have some ideas for a multichannel receiver of this type, which records the entire decay rather than just a few fixed channels.

Are there any other active projects of this nature?

[greylourie]

Pick up with the project.

Hi Matabele.

If you have a look at post 267, you will see that Bugwhiskers did finish the UIPM. It is a usable platform for anyone to experiment with, and all the important links to get started are in that post.

It is like a motherboard that anyone can build, and add on to.

The links to GPOZ would probably be best accessed if you registered and became a member there.

Hope that helps.

[matabele]

Dead Thread

I am a latecomer to this project - but am interested in its progress. It appears to be difficult to access the goldprospectingoz links, without which this thread is dead.

Anyone know where to pick up with the project?

[WM6]

HI BW.

Very promising project at beginning.

But what now? All stopped?

Always befits what has begun to complete also.

I support your creativity to get final solutions, so I am interesting to buy some kits or parts, whatever you offer (mono coil version only). Prefer to pay by PayPal.

Best wishess and best regards

WM6

[eneztr2005]

only one pcb and schema

my english not perfect

I want this project's one schema

complate one schema i will drawing isis (proteus) for simulate but not perfect electronic and i want you only 1 schema (all in 1)

i think understand me

[Derx]

Hi, bugwhiskers!

how to download firmware hex file?

[Wirechief]

Hello friends,

bugwhiskers and some very competent people are working on a very interesting gold detector project at the moment. I had the chance to check some internals of this project and it is really one of the most promising PI project. Check it out from time to time. When the server is down, then try it next time.

Aziz

Hi Aziz, I want to ask you a question, have you written any textbooks before? I saw one with the name Aziz on it. I am just curious. Thank you very much.

John Tomlinson,CET
John's Detectors