Another P.I. link

xavier

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	Re: Another P.I. link « Reply #150 on: September 11, 2011, 06:55:50 am »

Machineman DON'T touch that schematic yet LOL Hey Dooley just went though the schematic and did a thorough check with my PCB and guess what .................. well the problem is on your side there HAS to be a component left out OR a value that is incorrect but my board is 100% to your schematic and all components value are correct So if you would be so kind as to GRAB that schematic and do a counter check for the sake of my well being (Going nuts) Grin

I sure would appreciate it mate. By the way it's not just the UV that reacts on the photo sensitive material but also the frequency of the light so you can do the board under a neon light too but it takes a much longer time period plus minus 30 min Grin

Can you see me under a street lamp with my board in hand LOL I'd have the cops arresting me for loitering and THAT would only happen to me. Hey come to think of it there may be a connection left out (I wonder)

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DOOLEY1972

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	Re: Another P.I. link « Reply #151 on: September 11, 2011, 02:09:07 pm »

hello all ,

below is the schematic of the modified blind squirrel (with thanks to 6666)

i have put in the values ,cleaned a few things up , this is the version i first built and then tweeked a few values ,
this is the version that i was happy with , works 100% , with nice audio responce and quite stable .

below is also a pic of the curve on scope to aim for whilst adjusting the 100k multi-turn pot on the TL071

the scope scale is 2V and 10uS

you can see the sample point on the bottom line , center on this point , but widen to 20uS ,
then she is quite stable only minor reaction the ground.

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xavier

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	Re: Another P.I. link « Reply #152 on: September 11, 2011, 03:03:38 pm »

AHA found three different values so far and did not do a proper check R12 2k2 instead of 10k R13 22k instead of 47k C17 removed now I can see why I was having problems Grin

Will have a look into this once I'm in JHB my flight is at 08h45 tomorrow morning but as soon as I land I will be going through the PCB and change them components. Will let you know how it's going some time later.

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DOOLEY1972

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	Re: Another P.I. link « Reply #153 on: September 11, 2011, 03:48:31 pm »

HELLO XAVIER ,

items altered won't affect it regarding working or non-working

lower value of r12 speeds up reaction to target ,

r13 affects the gain of the last 741 , makes it react quicker to targets ,

and c17 slows down the reaction of the last 741 ,

non of the above are critical , would work with either of the values , just me playing to increace depth and reaction
to targets.

i'm wondering if conections on the 4066 are right , regarding what you tested and posted a while ago ,

happy landing's

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6666

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	Re: Another P.I. link « Reply #154 on: September 11, 2011, 10:22:31 pm »

Hi All
glad to see you are working out the bugs

Xavier, yes I did get Flowcode, have not had much time to play with yet
been looking for examples of pics flashing leds to see how to use it.

Ok on your pcb process thanks

Dooley thanks for update on leds , TINYCAD is a nice freebie
for drawing schematics.

The breadboard setup was ok untill I put the irf740 on the board
too much current made strange voltage drops

cheers
6666

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DOOLEY1972

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	Re: Another P.I. link « Reply #155 on: September 12, 2011, 01:19:45 pm »

hello all ,
added an external trim knob to the TL071 offset ballance for adjustment in the field ,

regarding the dual channel version with red green led's
once set up , works on the bench , and works well , but there is a problem ,
a nickle coin face up is green led , but edgeways on it goes red led ,
so if all lost coins land flat and stay flat then all is ok ,
alu and iron goes red led regardless of oriantation , so thats ok ,

BUT , in "the field" it's a differnt story ,
requires regular adjustment to the ballance knob to maintain red / green ballance ,
poss requires another sample point for ground ballance ,

going to re-make my coil first , as i'm getting allot of falsing ,poss coil movement in the case or bad connection ,
maybe the source of earlier mentioned interferance , not sure ,
anyway , time to do a shielded coil this time , may then get away without a 3rd sample for ground ballance ,

one thing i was thinking about when i get to build new coil was a "dual coil" both fed to control unit and switchable ,
so 300mm for general searching , and poss 150mm for pinpoining ,
then my other thought was to simply make a spider coil , big on the outside small in the middle ,
best of both worlds ?
and poss lower capacitance / faster than pvc bundle wraped coil ?

anyone got some good idea's for the "perfect coil" ?

Posted on: September 12, 2011, 11:39:57 AM

OH YES ,

forgot to mention led's no matter how big (i used 10mm's) no bloody good in sunlight ,

poss meter would be better in sunlight ,

problem is , whatever form of visual indication is used i'll end up looking at it all the time and not where i'm going ,

so thinking high tone , low tone , but detector starts off clicking , how to progress into either tone ,

clicking could be a fixed but pulsed tone replacing the clicks , increacing into full on tone weather high or low ,

so thats poss my best idea , easyest way would be use 2 ready to use piezo sounders high and low , using output of the audio 555 into 2x 4066 switch's , one giving a + and the other a - to respective sounders , and other end of sounders go to the red green op-amp.

or is this to complicated , picture below .

hang on , what about volume control ? hum ho , vari pot between pin 6 of op-amp and the join to sounders ?

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6666

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	Re: Another P.I. link « Reply #156 on: September 12, 2011, 04:30:40 pm »

Hi Dooley
keep going with the good work with the leds

Aziz has done some good work on DF coils
they are something I need to try myself
some good stuff here, he even did some tri field work

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They seem easy enough to make, the basic design seems to be
take your normal round coil halve the inductance
and build two two coils IE 10" and 5" .
So if your coil is 300uH, then 150uH + 150uH, turns going same way connected together.

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6666

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	Re: Another P.I. link « Reply #157 on: September 13, 2011, 07:18:05 am »

Hi
been doing some freq and pulse width measurements
with the pots on the 555 and 22nF cap
the designations width and freq are not right.
the width is altered by the 10k
and the Freq by the 100k.

I noticed that the pot and R on pin 7 to batt
used to be 10k and 10k
now they are 10k and 1 k

so the resister between batt and pin 7 alter the width
with 10k and 10k
the narrowest pulse was about 170uS
the longest was 350uS

with 1k and 10k
the narrowest is now about 18uS
and longest is about 183uS
I believe for gold the pulse width should be about 100uS

the freq varies with the 100k pot from about 320Hz to about 620Hz
the width pot varies the freq about 20Hz
cheers

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DOOLEY1972

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	Re: Another P.I. link « Reply #158 on: September 13, 2011, 11:53:29 am »

hello 6666 ,

yes the 10k pot on the 555 does the width , i altered my inline 10k to 1k to reduce maximum pulse width , which , with the 10k was far to much.

now max pulse width is about 190uS , and at 200 Hz draw is about 270mA which i rekon is enough for 9 hours use on 2500mA battery pack.

and the 100k pot does the freq , 200k total is about 200Hz , 100k total is about 400Hz , removed my trim pot for 2x100K's inline as i feel 200Hz is about right , good responce whilst sweeping and acceptable power use.

yes the width pot varies freq a little , a little draw back of this arangemant of the 555 ,

your getting higher freq than i did , wonder if i have misread the cap i used for C1 , poss try a slightly bigger one 6666 ,
unless your happy with high freq ,

regarding pulse width , poss should have used a fixed resistor that would have "centered" pulse width into a useable area ,
if 11k = 183uS and 1K = 18uS
then poss , based on a simple ratio calculation ,
if pot is a 4.7k and fixed is an 8.2K total = 12.9K
max = 12.9K= 214uS
min = 8.2K = 136uS

you mention "frequency for gold"
as far as i have read , there is an ideal area of frequency for different metals when using sine wave's ,vlf / IB etc...
but have never read anything regarding ideal frequency for different metals regarding a PI ,
we should refere to frequency on PI's as "pulse repetition" not frequency ,
as each individual pulse just samples the target , more pulses , more samples , but each pulse is on it's own ,

on geo , mikebg had allot to say about this subject , and cleared up some confusion , that each pulse is on its own , and frequency is not the correct term , and no pulse has an effect on another pulse (unless they run into each other)
hitting a target with a pulse , sampling , target signal dies , then is hit again and re-sampled.

anyway , that's the gist i got .

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machineman

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	Re: Another P.I. link « Reply #159 on: September 13, 2011, 01:32:12 pm »

Hi Dooley what gauge/size wire are you using to wind you search coils.
thanks

Posted on: September 13, 2011, 01:23:24 PM

Hi Xavier have you managed to get the components changed out and had success

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