Universal PI Micro

[Ray-NM]

I like it.
Raynm

[bugwhiskers]

Screen option

The attached pic shows an example layout for the 64 S&H PI / UPIM.

The LCD is 128*64 dots.

The top left box shows the 64 samples (actually a couple less due to the box lines) The top right box is a zoom window of 8 of the samples of the left box.
The bar graph in the middle is signal strength and the 6 digits are user adjustable variables.

I am waiting on a couple of 240*128 dot screens to arrive, these will allow double the resolution and allow more room for other "things"

regards

bugwhiskers

[bugwhiskers]

Hi BW is this an addon to your previous published cct?
or a new homebrew?
johnno

Hi Johnno,

It's very new. The preamp stage is much the same as other PI's with the exception of a fast first stage and a fast high current drive for the second stage to charge/discharge the caps. Everything downstream is different.

regards
bugwhiskers

[Ray-NM]

BW
Looks like a very efficent way to get the data. That is the problem I am having with the Basic Stamp it is too slow to process the signal immediatly.
I will think on your approach and see if I can implement it your way.
Great Idea.
RayNM

[johnno]

Hi BW is this an addon to your previous published cct?
or a new homebrew?
johnno

[bugwhiskers]

UPIM update

Hi Ray,

I have tried to make at home a PCB of the circuit board posted earlier and it is just too tight, small tracks, no meat on the pads so I have decided to make the board larger. This will also make it easier for folks to make their own from the artwork. I have also decided to use a 40 pin DIP chip that will again make life a lot easier for the homebrewers.

With regards to the other project, the following is a brief outline:

The front end preamp, coil drive and damping resistor are the same as in most PI circuits, but thats where the similarity ends.

The circuitry following the preamp gets 64 samples (via switched capacitors) of the early part of the decay waveform. The time between each sample can be as low as 100nS. At that speed it is possible to capture 64 samples of the first 6.4 uS of the decay waveform. The capacitors are then switched in turn to the AtoD of the micro and the digitized result is stored in RAM.

One area of RAM holds an average of all the previous samples with user adjustable software lag and another area holds the most recent. The lag is necessary to prevent small changes being swamped by the averaging. Ground signal and preamp drift will become part of the average set of samples whereas any abrupt change will be seen as a target. Because the sampling is done very early in the decay it should be possible to discriminate.

What is unique about this approach is the the samples are gathered very quickly and then later processed at leisure between the TX pulses. This technique obviates the need for a super fast micro and a super fast AtoD.

The 10uS per division CRO shot shows, in the bottom trace and to the left, the 64 samples being taken (6.4 uS). The rest of the trace shows the time taken to digitize them and store to RAM.

regards
bugwhiskers

[Ray-NM]

I for one would like to know what your idea is, I have looked at the decay curve for iron and have wondered a few things myself.
Which ever you decide -go for it.
RayNM

[bugwhiskers]

Hi guys,

When I started this project I was very focused and things progressed. A little while after this I had a rush of blood to the head and figured out an easy way to really capture what is happening in the decay curve. I am comitted to finishing this project but I am at loggerheads with the new idea as it has so much potential. Bbsailor and myself have had a lot of dialogue and he has been a real inspiration and help. I live in an area of Australia that has no shortage of gold to be discovered, as I speak there is talk of a specimen of gold with quartz being found very near where I live that is around 1000 oz of gold, the largest ever found with a metal detector.
I have been out with commercial detectors and a bucket full of axe heads, horse shoes, bullets, shoe tacks etc etc was the result.
I guess, what I am is asking is... do you want me to proceed with this project to it's conclusion, or do you want me to disclose the idea that has real potential and publish the circuit ?

regards
bugwhiskers

[Qiaozhi]

Hi Qiaozhi. I am 47 years old, i have 3children (boys...the first is only 9 years old), and i make 2 jobs for a good sallary. At free time it is better (for me) to construct any detector or to drink whisky or wine. I started to learn how to program the PIC but i never finished it . What to do ... the years are years .....

It's never too late to learn.
The "two jobs" thing might be a problem though.

[Geo]

What's stopping you from starting now?

Hi Qiaozhi. I am 47 years old, i have 3children (boys...the first is only 9 years old), and i make 2 jobs for a good sallary. At free time it is better (for me) to construct any detector or to drink whisky or wine. I started to learn how to program the PIC but i never finished it . What to do ... the years are years .....

[gef12]

HI BW
Just keen for this to happen. Hats off to you BW. Am also angry at meself for not getting into programming Something like this should inspire us all.
So will sit back patiently and wait for it to blossom.
cheers
gef in OZ

[Qiaozhi]

When i see projects as this i am angry with myself because i never learned to program microcontrolers

What's stopping you from starting now?

[Geo]

Perfect work . A few components yet and we have a very good PI detector with a lot of adjustable parameters. When i see projects as this i am angry with myself because i never learned to program microcontrolers
Congratulations bugwhiskers
My Regards

[johnno]

wow

Sorry BW, I was not trying to correct maths,just That I dont understand the enormity of what you are creating..I will sit back and wait to see how your project pans out..(no pun on Gold panning).
Johnno

[bugwhiskers]

Hi Johnno,

The 638 is just a number plonked on the screen to show where the digital signal strength will go. Only N,S,E,W and C(centre)will be recognised.
Pressing all the buttons at once will generate a very low number.

To allow for the offset mentioned in an earlier post there will be another adjustable number just to the right of the signal strength. It will allow the user to optimise/centralise the bar graph for maximum sensitivity.

Things have changed a bit since original conception. There will be 8 user adjustable settings:

1: Pulse width
2: Cycle time (time between pulses)
3: Delay 1 (first sample after pulse)
4: Width 1 (width of that sample)
5: Delay 2 (second sample delay after first sample)
6: Width 2(width of that sample)
7: Offset (for bar graph)
8: Low battery voltage (crucial if you are using LI/LiPo batteries)

There will be 3 screen pages.
7 and the bar graph are on the first page called Search.
1 to 6 are on the second page called Adjustment.
Battery Low Voltage adjustment will be on it's own page with room for more if needed.
With 8 user adjustable settings requiring 2 bytes each there will be room to store 32 sets of favoured adjustments in the on board 512 byte EEPROM (retained with power off) memory.

regards
bugwhiskers