Universal PI Micro

[bugwhiskers]

Hi BjBj,

I am a bit perplexed. You want to see the noise from a defunct platform and you don't want to see a video of the new platform working well.
Because the software compares the relativity of the samples to previous ones, drift due to temperature doesn't matter.
Most PI circuits use a 555 or similar for the audio. Because the 555 is connected to ground, any change in threshold from earlier stages will necessitate some sort of constant adjustment if the audio threshold is to remain constant.
If relativity is used it generates a number that is fed to the micro's internal PWM for the audio and drift due to temperature or whatever is no longer part of the equation.

regards
bugwhiskers

[bugwhiskers]

Hi BjBj,

The pics show the 80mV noise in the decay curve of the bus prototype. Adding filters to diminish it also reduced the usefull signal and therefore sensitivity. The forum members that voted also requested a ready made platform and the one chosen is shaping up well..... you can see for yourself if you care to look at the video.

regards
bugwhiskers

[BJBJ]

bugwhiskers;

>I am a bit perplexed. You want to see the noise from a defunct platform >and you don't want to see a video of the new platform working well.

I wouldent mind see it, its just that im on a very slow modem line
to the net. Thats all!

Why is it defunct?

>Because the software compares the relativity of the samples to previous >ones, drift due to temperature doesn't matter.

?
The samples after the previous vill drift to.

>Most PI circuits use a 555 or similar for the audio. Because the 555 is >connected to ground, any change in threshold from earlier stages will >necessitate some sort of constant adjustment if the audio threshold is to >remain constant.
>If relativity is used it generates a number that is fed to the micro's internal >PWM for the audio and drift due to temperature or whatever is no longer >part of the equation.

Im not talking about the audio detector side of it, im talking about all the components that are involved in your new detector, the mux, the caps etc.

Rds of the mux will vary for instance. The idea are, calibrate it away!
Im talking about the ide of yours to use 24bits of resolution, or even
16 bits are a pain to reach in an enviroment that changes.


regards
BJBJ

[BJBJ]

Hi BjBj,

The pics show the 80mV noise in the decay curve of the bus prototype. Adding filters to diminish it also reduced the usefull signal and therefore sensitivity. The forum members that voted also requested a ready made platform and the one chosen is shaping up well..... you can see for yourself if you care to look at the video.

regards
bugwhiskers

I do care to see videos if i could, no need to be short in the tone!

Now im perplexed!!!

Which detector are the pictures from ?

The one with 10bit AVR MCU and 24mux sample channels or
from the Aduc with 24bit ADC and 24mux sample channels?

Besides how much of that decay curve are capacitance gate charge?

regards
BJBJ

[bugwhiskers]

Hi BjBj,
The decay curve CRO shots are of the old bus prototype using the ATMEL chip. The noise and the difficulty for forum members to make the boards caused it to be defunct.

The samples will be taken at about 5ms intervals. How much would you expect the temperature to change in 1/200th of a second ?

You really need to take me up on my offer of a video of the stability of the platform.

If my tone seems harsh it is probably because I have asked you before to offer alternatives if you don't like the current direction. Constant criticism when you haven't seen the proof or offered an alternative is a bit hard to take.

regards
bugwhiskers

[Wirechief]

Hi Bugwiskers, I have gotten in a bit late on your project. I wonder are you going to selling boards for the project when all is checked out? I hope you will keep going with it and look forward to your results in a complete unit. Ok God Bless and good luck. I am going to try and keep up with your project. Thank you BW.

John Tomlinson,CET
John's Detectors

[BJBJ]

[quote=bugwhiskers;54436]Hi BjBj,
The decay curve CRO shots are of the old bus prototype using the ATMEL chip.
The noise and the difficulty for forum members to make the boards caused it to be defunct.

>The samples will be taken at about 5ms intervals. How much would you >expect the temperature to change in 1/200th of a second ?

Not fraction of a second, im talking about over minutes of use!

>You really need to take me up on my offer of a video of the stability of the >platform.

Im not questioning your video or the offer, provide me with the means
to download 18Mb i gladly have a look at it.

>If my tone seems harsh it is probably because I have asked you before to
>offer alternatives if you don't like the current direction.

Geee,man!

I constantly giving hints about possible pitfalls in a way for you to be aware
of these, i even dig into datasheets to help out and all you do is complain!
If you don't like that just say so and i will not give a **** about your project
anymore if thats fine with you?

> Constant criticism when you haven't seen the proof or offered an
>alternative is a bit hard to take.

I have given alternatives but you don't even give a answer to my suggestions!

Perhaps you have to start to see clearly that what i write are not
constant criticism of what you do is rather the opposite (stated above).

You said in previous posting that your ego was low, i now recall the
opposite, with your last posting that its so high at the moment that
you cant even take the facts from the data sheets but see's that
too as a criticism of your project!

Call AD and complain to them then!

BJBJ

PS: Posting 128 says: **Splendid***, your doing fine!
Are that complaints too?

[bugwhiskers]

Hi Wirechief,
Thanks for your interest in the project.
The whole idea of using a readily available board was to save the nuisance of having to get boards made professionaly and then maybe having half of them sitting on the shelf forever.

At present I am working on a plug in board that will hold the sampling cap multiplexer (74HC4051), the coil pre-amp and the coil switching circuitry.
The board is very uncomplicated so I will post the info so users can make their own.

The board will allow a maximum of eight samples to be taken and stored in the micro for processing. It will allow either a "P" or "N" channel MOSFET to be used as the switching element. Similarly, the pre-amp will have universal offset nulling circuitry so a variety of pre-amp chips can be used.

regards
bugwhiskers

[bugwhiskers]

Hi BjBj,

The DC offset voltage output from the pre-amp is an "absolute" and will change with temperature. Taking samples at 5mS and comparing them with the previous sample is a "relative" comparison and unless the temperature change is faster than the sample period then temperature drift is ignored.

A simple analogy of this is imagine you are in an elevator with another person. The elevator is going up slowly (absolute). The other person is jumping up and down inside the elevator and you can clearly see that (relative). You are only aware and interested in the height difference between you and the other person when they jump(a target), your height above the ground is unknown and irrelavent(absolute).

The software algorithm is performing the same function as a DC blocking capacitor to the DC offset caused by temperature change while allowing AC (changes from one sample to the next... a target) through.

regards
bugwhiskers

[BJBJ]

I dont find the link to the video?
Dont PM it, upload it "sowhere" instead!

Regards
BJBJ

[bugwhiskers]

The owner of Prospecting Oz has kindly uploaded the video to his forum site in an area called "Files" There is a link in Geotech to "off site" forums that will take you to Prospecting Oz.

In order to see it you will first have to register to enable that section to become available to you. While you are there take the time to browse some of the many other prospecting related files and posts from some very knowledgable members.

The file is called "DSCF7091.MPG" and is around 2mB in size.

What it shows is the stability of the ADUC845 evaluation board. A wet finger is alternately placed on the connectors to the adjustment pot and then removed. You will see the noise from EMI and when the finger is removed the readings revert back to their steady 24 bit values.

regards
bugwhiskers

[bugwhiskers]

The attached pic shows the UPIM plug in board atop the evaluation board.

Bottom right is the LCD display header with the red resistor network pullups just above it and the blue contrast adjustment pot slightly to the left.
Top right is the pre-amp and associated components.
Top left is the 74HC4051 muliplexer for the caps/AtoD inputs.
Bottom left is the MOSFET (IRF740), the mosfet driver and -V generation circuitry. The signal from the micro to "pump" the -V circuitry is disabled during sampling and AtoD conversion to minimise noise. Likewise, no data is sent to the screen during this period.
A commercial double "D" coil is arriving this Friday so I can start doing some tests.


regards
bugwhiskers

[Unregistered]

mohsen

hi all-i need a shematic& part list &pcb for print(metal or gold detector -plase help-plase write adress

[bugwhiskers]

Hi mohsen,

I think it wise to wait until it is finished and working well.

regards
bugwhiskers

[Unregistered]

hi-i need a shematic& part list &pcb for print(metal or gold detector -tank you for answer regards bugwhiskers