Universal PI Micro

[bugwhiskers]

Decision time

For those who have been following the thread I thank you. It has now come down to crunch time, what direction next.

The 64 sampler has shown it can discriminate, it can see the difference between Lead, Steel, Aluminium & Gold and Silver.

Those of you who have followed the project from the start will know that it started out as a Universal PI micro to control the main timing functions of PI's. My focus changed when I hit on the idea of switched capacitors quickly gathering samples of the decay curve for analysis between the TX pulses.

To fully exploit the discrimination capabilities of the multiple sampling approach the PCB will have to be re-designed to minimise noise so it can have very high gain with the analogue and digital sections well segregated.

What I would like to know by way of a vote is how many are interested in the 64 sampler as a dedicated discriminating PI with professionaly made PCB's and how many are interested in having the UPIM to experiment with PI in general ?

Your vote will help me decide where to best put my next efforts.

Thanking you in anticipation of your vote.

regards

bugwhiskers

[bugwhiskers]

A new idea.

I got to thinking last night about replacing all the chips that make up the 64 sampler with one chip, an older style dynamic RAM chip. These chips have the switches, capacitors and decoding logic all inside. I have found that the 1 nF caps are more than ample so even if the dynamic RAM chip caps are much smaller it should still work. A 74HC4053 would still be required to toggle from pre-amp to caps and caps to AtoD.

Tomorrow I will do a web search and see if I can find one that could do the job.

regards

bugwhiskers

[bugwhiskers]

Hi Alexismex,

Thanks for your interest in the project.
I have changed the first pre-amp back to an LM301 and it definately needs a small feedback cap.
There is much work still to be done before any boards are made and put up for sale. The gain needs to be increased (currently 2000) and noise needs to be minimised if the discrimination is to work with small/distant targets. Don't be surprised if the final setup for the 64 sampler is a single PCB to achieve all the necessities.
Because steel produces greater curvature of the graph it will smother the signal from nearby non-ferrous targets, nothing we can do about that, it's Physics obeying Murphy's law.

Next week I am going to test the detector on some red clay that causes Minelabs and other detectors to give a false signal. Because it is not metal I am hoping it's "conductivity" is very different from desired targets.

regards

bugwhiskers

[Alexismex]

hello bw,very interesting project,nice to share your work ,definitively put me in your list for 2 boards and micros, just a few detail : i make many test with or without a small cap (3.3pf ) in parralell with preamp 5534, not necessary ,give less sensibility to the preamp.
your project give us a good view to digitalise PI to true discriminate metal via visual lcd panel good idea .I like very much your approach to not complicated your project with memo signatures etc...just to see in real time the metal signature ,and we use our brain to determine which metal is .
Have a very good time and nice working

Alexis.

[BillA]

bw, congrats
one h*ll of a project
I'm in for several sets of boards when available (figure I'll screw one up)

Thanks, Bill

[bugwhiskers]

How the descrimination works.

Each TX cycle the capacitors are sequenced and the voltage for the current position on the decay curve is stored in the capacitor. Each 10th(user adjustable) TX cycle a routine is called that sequences the caps again and gets an AtoD reading of the voltage on each capacitor. This reading is compared with the previous reading for that capacitor and the difference is stored in a RAM location called "DIFF". The previous value was stored in a RAM location called "PREVIOUS" and the current reading is added to it then divided by 2 and stored back to "PREVIOUS".
Each TX cycle a routine is called that displays a dot graph representation of the string of numbers stored in "DIFF".

When silver (the best conductor) is the target the curve on the screen is relatively slight. Al and Gold produce a more pronounced curve and Steel produces a very strong curve. Essentially the graph is showing the "conductivity" of the target. There is still a bit of work to do in putting in place a software filter that will exclude curves of targets that are of no interest or a method of displaying a conductivity graph as an indicator of the target material.

The new micro and screen should be up and running sometime this weekend. I am hoping it's larger size and greater contrast will allow some good pics to be taken.

regards
bugwhiskers

[bugwhiskers]

Drool time.

The pic shows the UPIM with the 64 sampler boards in place. The kind gents (members of the Prospecting Oz test team) allowed me to test discrimination with the nuggets pictured and I am pleased to announce that there is a distinct difference in the shape of the graph on the LCD screen between any of the nuggets and a block of steel.

The micro's turned up today too so I have a bit of work ahead of me.

regards

bugwhiskers
PS The largest of the nuggets pictured is 17 ounces.

[Ray-NM]

Waiting for Pic's and an update.
RayNM

[bugwhiskers]

UPIM/64 sampler update.

It's been a while since I posted so it's time for an update.

The preferred micro with 4 times the RAM should be turning up this Friday. This will allow me to show the full 64 samples and on the larger
240 * 128 dot LCD screen too.

About the same time a couple of nice fast sheilded coils that bbsailor has very kindly made for me and posted should arrive.

Tomorrow, a couple of detectorists (not to be confused with terrorists) from the Prospecting Oz forum will be coming to test the 64 sampler with some largish nuggets (hope to get some photo's of that). I am looking forward to seeing discrimination between a block of steel and the nuggets.

Stay tuned.

regards
bugwhiskers

[bugwhiskers]

UPIM bus plugs and sockets

The attached pic shows the unpopulated bus sockets. Shown also is the pinhead connector. These type of connectors are the simplest, cheapest and most readily available.

regards

bugwhiskers

[bugwhiskers]

Hi Functional,

Thanks again for your interest in the project.

In my workshop I have about 20 different circuit boards that I have made to test out different types of PI detector experiments over the last yerar or so. Each of these circuit boards has a lot in common ie micro, mosfet driver, charge pump etc etc.

The UPIM motherboard holds all the parts/functions that are common in a PI detector and also 2 bus sockets that allow a user to add things that are different to his/her design.

Importanly there is also provision for a Graphic LCD screen where experimenters without the luxury of a CRO can see things like the shape of the decay curve.

What it allows me to do is change plug in boards without having to re-make the whole thing which is what experimenters really need.

If you fancy the Hammerhead or Gary's PI you are probably better off buying their circuit boards and populating them. However, if you want to experiment with major hardware changes, augmentation and display various parameters then you could hook them up to the UPIM via the bus.


regards

bugwhiskers

[Functional]

Hi bugwiskers.

As a non-guru in the field of electronics, I was just wondering if you had considered working with one or more of the PI designers to make a simple plug-in interface, so that anyone who builds your board can easily plug it into they're PI board? Maybe using either a fixed position slot type plug, like an isa card and slot interface, or a cable and plug arrangement like those used for harddrives. Even a USB style connection, with a very short cable, would be possible?

Something cheap and plentiful would obviously be preferred to some proprietary and expensive connection. I don't know if people would want to "hard wire" the two together, as that would leave no option in the event something were to go wrong, or get damaged, short of disassembling and possibly desoldering in order to track down the problem.

Thought I'd throw the idea out there to see what might have been considered already. It just seemed to me that everyone was working on they're own project, without considering that aspect and those who will have to assemble and possibly adapt them to the use of your board, (or visa versa), later on.

Just planning ahead for any eventuality.

F.

[bugwhiskers]

64 SAMPLER SCHEMATICS

The attached .PDF's are the schematics for the 2 boards that make up the UPIM 64 sampler. IC1-IC6 74HC4051. The #2 board has no bus connector, it "piggy backs" on the back of the #1 board and sits very snugly above the micro. This arrangement works but isn't very elegant. Using SMD, all the components will fit very easily on one PCB and the other side of the PCB could be used as a ground plane/shield. Notice AD7 is available and could be used to control the additional chips to make a 128 sampler if deemed beneficial.

regards
bugwhiskers

[bugwhiskers]

Hi Functional,

Thanks for your interest in the project.
Atmel, the makers of the AVR micro's have a complete suite of programs and devices that make it very easy to get into it. I use a device called an
AVRISP II, it's about the size of a PC mouse and acts as an interface to your micro for programming. At around $50 including their AVR studio software its a real bargain. There is also a forum site called AVR freaks where all of your answers as a beginner will ne answered very promptly.

I will be posting the source code for the UPIM here. It will have lots of useful routines like driving the LCD display, reading push buttons, controlling the charge pump, switching the MOSFET on and off, etc etc etc. Users will be free to change the code to suit whatever they are trying to achieve and hopefully they will share their knowledge and experiences.

regards

bugwhiskers

[Functional]

I've just read through this thread and found it very interesting. I know you mentioned the software you were using, but I'm not familiar with it. Have you heard of the open source program called "Great Cow Basic"? It can be found here:

http://gcbasic.sourceforge.net/about.html

I've done some programming for use in Dos programs and was thinking of learning xBasic, but I have too many demands on my time. I also wondered if you had heard of the software called "PicAxe"? It seems to come with alot of options for projects and tutorials. It's free for personal use and can be found here:

http://www.rev-ed.co.uk/picaxe/

I tried to download PicAxe a couple of years back, but I was and still am on dialup. It's 27 Mb's and kept timing out after about 7 Mb's. Sure looks interesting though. And with all the project options and blank PCB's available, I thought it might be something worth learning, (or at least trying to learn).

Just thought I would mention, that if there are patents, or other legal issues involved relating to intellectual property, having the rights to the application of a finished product, doesn't stop you from allowing others to construct and use it for person use. I've seen some licenses to that effect in the past and its sort of similar in wording, to the software agreement that PicAxe has.

Keep up the good work.

F.