Universal PI Micro

[1843]

Hi okantex,

Tell me please, do you have an Oscilloscope ?

regards
bugwhiskers

Hi,
He have no oscope,

Regards

[bugwhiskers]

Hi okantex,

Tell me please, do you have an Oscilloscope ?

regards
bugwhiskers

[okantex]

and the biggest problem in my mind iswhat is saturation of premap?
how do you understand it is finished.what sort of process lets you understand it?

[okantex]

Hi Bug.
what is the voltage when preamp is in saturation.is it around 3.5v when there is no metal around the coil?

can you give timeing of your software.

[bugwhiskers]

Hi okantex,

The signal that is presented to the analogue discrimination circuitry must range between ground and the +5 of the Op amps/Micro.

Take the first sample when the decay curve is at about 0.5 volts and the second one at 0.27 volts. The second sample is amplified by 2 so the output at the final stage will be just above 0 volts. Any Steel bought near the coil will then cause the first sample to go above the second causing a negative output and exactly the opposite when the target is Gold or Aluminium or anything that is a better conductor than Aluminium. Use the position of the second sample to get the adjustment correct. Use 10nF caps and a pulse sample width of about 1uS.
I hope you are starting to get the idea of how it works.

regards
bugwhiskers

[okantex]

and something else
do you feed just positive signal to mux.
cause you can not feed negative to adc.

[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 .

[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]

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]

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

[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

[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.

[okantex]

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

[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]

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.