Universal PI Micro

[okantex]

Hi Bugwhiskers
I can not understand term signal strenght.
what is it and how do you measure it.
is it integral of a certain(preset) period.

do not you need to get samples to see full delay time to have discrimination.

and one more question.
I could not understand term saturation for opamp.
but I see you are takeiiing samples from the begining of knee(yield point)
how do you decide to start sampling,I mean how do you understand the time for sampling occurred

[okantex]

BTW
did you chabged screen.
you are just talking aabout two vertical bars.
according to your explanation. I see almosst everything clear accept silver.

how do you make up this bars. can you give formula
cause your silver discription looks like what expect from copper.
for silver I was thinking seceond bar much lower than iron.

still wonder what about decay time measuring to see delay.

[bugwhiskers]

Hi okantex,

It's very late here, tomorrow I will make a drawing and post it.
The signal is related to the conductivity of the target with Lead and Steel being at one end and Silver at the other with Aluminium and Gold at the pivot point as set by the positioning and weighting of the samples.
It sounds terribly complicated but in reality is ridiculously simple.

regards
bugwhiskers

[bugwhiskers]

Hi oktanex,

The attached .PDF will help explain the processes.

Things to note:
Sample 2 is amplified by 2 and the position (pivot point) is adjusted so with an Alum/Gold target the output of a differential amplifier fed with samples 1&2 produces a zero or slightly positive output. Any metal type with less conductivity than Alum/Gold will then produce a negative voltage.

The labelled curves are indicative of the flattening of the decay curve with increasingly conductive targets.


regards
bugwhiskers

[okantex]

is the pivot point in the first 6.4us of knee.
according to delay graf . it looks like at 150us .

and for bars did you divide 64 samples to two 32 samples. than average of two group makes two different bars.
Am I right.?

[bugwhiskers]

Hi okantex,

There are now only 2 samples required. I started with 64 thinking it was going to be very complicated and it ended up being very simple.

The sampling can start almost anywhere in the knee and away from the saturation, it's the positioning of the second in relation to the first that is important.

The pivot point is set to be the point where the user wants the signal to change from negative to positive. The change to negative with Steel and Lead is far more pronounced than the very slight change from Copper to Silver.

The attached .PDF is a rough schematic of the circuit to achieve the discrimination. The 2 samples are positioned so that with Aluminium as the target the final Op amp output is slightly positive. Steel and Lead will then cause a very strong shift negative and Copper and Silver more positive.

regards
bugwhiskers

[okantex]

Hi Bugwhiskers,
I want to ask a few questions again

1. how does bar graf. change with the change of metal size and distance.
does it effect discrimination.

2. what is signal strengh .how do you form it through delay curve

3. I want to see and learn how to control switch of caps.74hc4051 multiplexer/demutiplexer .
how to charge and lead to adc .

can you give algoritma that you used to write your program.
I just know pıcbasicpro.can understan C,but not hex or assembly.
do you have something for me to understand what is happening step by stpe.

[bugwhiskers]

Hi okantex,

Forget about the old bus prototype and the 64 samples, it turned out to just be a tool to discovering how to discriminate simply.

With the OP amps doing the discriminiation and producing just one output signal then only 1 bar graph is required and that indicates signal strength. The audio will be fed with that one signal also to give audible target strength info.

Tomorrow I will draw up the full schematic including the 74HC4051 for switching the 3 caps for sample 1, sample 2 and ground balance.

When adjusted correctly Steel and Lead should not be seen or heard and the bar graph/audio will indicate the signal strength of the target.


regards
bugwhiskers

[okantex]

okay .but does the size of metal and distance effect result.
are these results just for coin hunting.

[okantex]

If you just take two samples from middle of delay graf.
when a big target is found your two bars will be high and equal ,even it is iron.

but target is always a nugget or coin wont be a problem.
but how can you know . is it iron horse shoe or gold nugget than.
or a big gold statue.

[bugwhiskers]

Hi okantex,

If the target is large/close the pre-amp will go into saturation and discrimination will be lost, the easy fix is to raise the coil and discrimination will be restored and the screaming audio will subside.
The relativity of the shapes of the curves for various metals don't change with different target sizes/distances, just their amplitudes.

regards
bugwhiskers

[bugwhiskers]

The attached .PDF shows the pre-amp feeding to the MUX and 3 storage caps. Sample 2 has a gain of 2 and the position of it's sample is adjusted for a slightly positive voltage at the final stage. Ground balance adjustment is achieved by varying the position of the ground sample in software.

With a target whose conductivity is less than Alum/Gold the output will go negative. A diode on the output will limit the negative excursion to protect the AtoD input.

Please note the analogue approach hasn't been tried but it mimics the software technique used in the prototype.


This schematic is preliminary and the actual pins used may vary to simplify board layout.

regards
bugwhiskers

[okantex]

is this analog unit.
1. I could not see any output for audio.at the end of IC4
2.you still control it with software but can not see way to ADC of PIc.
is PIC just for timeing of switch.
where will we take samples.at the knee I mean first 6.4us

how to control PIC.do we still need atmega644 or will 16f877 be enough

[bugwhiskers]

is this analog unit.
1. I could not see any output for audio.at the end of IC4
2.you still control it with software but can not see way to ADC of PIc.
is PIC just for timeing of switch.
where will we take samples.at the knee I mean first 6.4us

how to control PIC.do we still need atmega644 or will 16f877 be enough

Hi okantex,
The output goes to the AtoD converter to be converted into a number then fed to the micros PWM for audio.

The circuit isn't complete, it just shows the analog method of discriminating and ground balance.

Unfortunately I don't have the time to customise the circuit for all types of micros. The circuit shown is for hooking up to the ADUC845 evaluation board and it is the only platform I will be supporting.

regards
bugwhiskers

[okantex]

Hi Bugwhiskers,
what is the timing graf of this new 3 cap unit.
are all samples taken from fşrst 6.4us area of curve.

or something like first at 8th microsececond after knee yield point
second at 30th us .