Another P.I. link

DOOLEY1972

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	Re: Another P.I. link « Reply #160 on: September 13, 2011, 02:16:08 pm »

hello machineman ,

i have been using "hook-up" wire , from maplins in the uk , £6 or £8 for a 100m roll ,

it's 0.6mm dia , equiv to between 22-23 swg , covered in pvc insulation of 0.15mm , total wire thickness is aprox 0.9mm
it's copper wire that is silver in colour , tin covered i think .

most designs i have read about use either 22 swg ,24 swg or 26 swg , allthough some out there have used 18-20 swg ,now that's thick wire !

i started using insulated wire after i read a page on building "fast coils" on geotech ,
sepperating the individual coils by common belief is benificial ,
teflon insulation was apparantly the best stuff to insulate and sepperate the individual coils ,
but pvc is quite close , and still better than close wound magnet wire ,
besides that , apparantly the enamal coating on magnet wire only rated for about 100V ,
and a PI may go to 400v-600v ,
magnet wire ok if winding a tesla coil , as only one turn away touching another turn away ,not much voltage differance ,
but when bundle wrapped tight , like in a PI , if IN and OUT wires are close ,then it's a problem ,
i have had arcing ,
apparantly the hook-up wire has been tested to 1000v ,

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xavier

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	Re: Another P.I. link « Reply #161 on: September 14, 2011, 02:02:29 am »

Hi guys

Well the trip was a total B*#&y disaster but I got here OK Now for the important stuff Dooley I changed them components and now it works the only thing is that I do not get the clicking at all I wonder if that have not to do with the transistor that I used BC547 or is it 548 any how what I would like to know is what did you use?

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	Re: Another P.I. link « Reply #162 on: September 14, 2011, 02:07:17 am »

Congrats on getting it working

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xavier

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	Re: Another P.I. link « Reply #163 on: September 14, 2011, 02:16:57 am »

Thanks but I still have an issue the resistor to ground Dooley removed it well if I do that then it stops working all together and I don't get the clicking sound at all but that could be the transistor that I used, but all in good time we are getting there Ho I should have mentioned that a spider-web coil is no good as a TX coil but excellent as a RX coil.

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	Re: Another P.I. link « Reply #164 on: September 14, 2011, 07:30:05 am »

Hi Dooley thanks for the heads up on the wire, will also look at the aircraft wire # 24 that I have worked with has ETFE insullation should handel the 1000v alright but the insulation is really "tough" and will handel the close tight packing senario well.

Posted on: September 14, 2011, 07:22:56 AM

Hi Xavier please let me know when I can get the Poitive 20 out and start building, trolled through the boxes of parts and surfaced with most of what is required.

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DOOLEY1972

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	Re: Another P.I. link « Reply #165 on: September 14, 2011, 11:26:52 am »

hello all ,

machineman , the ptfe insulation i think is as good as the teflon if i remember right ,
tight packed wire with insulation to sepperate wires is apparantly the best way ,

great news xavier , detector working ,
the resistor to earth , was that on the threshold pots ?
that was to adjust the voltage to within range of the voltage you mentioned you were getting at the output of u5a ,
you can alter fixed resistors to your taste for best range / responce ,

NPN for the 555 , i have used 2 different ones so far , both the same , a BC337 and a BC639 ,

cheers for the heads up on the spider coil , have seen a few people use them , so i thought maybee i'd try ,
maybe not then ,
choices were standard bundle wrap , spider , or flat plannar ,
flat plannar ,arn't they more sensitive in the middle ? which makes me think poss not good for depth ?
or stick with easy to make bundle wrap ?

clicking depends on gain of the last op-amp set by the 47K / 22K ,
when i used a 47K i found a coin increaced the clicks for 5 inches till it was a note ,
a 22K clicks increace quicker to note , so had about 3 inches between clicks starting to increace then note ,
personal choice i think , but using the 47K should allow the threshold to be set for slow click ,
i like it that way , then obvious when in use if the clicks stop she needs threshold adjusting , again.

if she stops working with the resistor to earth removed and then the pot directly earthed ,
sample voltage must be higher than threshold can go ,
so either also remove the 22K to + and connect pot direct to +
or adjust sample point to a lower voltage point on the decay ,
or , best idea , adjust 100K pot offset on the TL071 for a "flat top" curve ,
then you can sample anywhere on the flat top without much variation / threshold adjustment required.

oh well , off now , back to thinking about coils , which one is best ........hmmmmmmmmmm.

Posted on: September 14, 2011, 11:25:14 AM

forgot to say , machineman , that wire sounds like the good stuff , people going to be envious.

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xavier

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	Re: Another P.I. link « Reply #166 on: September 15, 2011, 04:09:32 am »

Hi Machineman, Dooley

PCB is not at fault so you can go ahead and make it Hold it did I post the latest one? OK will post it any way I just want to go though the components list before I re-post it though. I still would like to do some more tests with the one that I have as the prototype is on vero board and mine on PCB there are adjustments to be made Dooley basically has a double sided board as he has it at the moment with tracks going over one another. I just remembered when I cleaned up the board I moved some components round a bit and I found that there is a diode making a short so let me fix this up first before I post it. Must go now to tend to my cheese LOL

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	Re: Another P.I. link « Reply #167 on: September 15, 2011, 06:32:06 am »

Hi Dooley and Xavier many thanks for the feedback re wire and the pcb schematic will see your post when done Xavier have fun with the cheese production!

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DOOLEY1972

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	Re: Another P.I. link « Reply #168 on: September 20, 2011, 01:46:16 pm »

hello all ,

funny thing this , and there is proberbly a logical explination ,
been having some funny things happen , interferance ,horrable scratchy sound , false tagrets , generaly "to twitchy" recently ,

so ,detector is the above mentioned modified blind squirrel , 200Hz pulse , coil 2.0 ohm , 527uh ,

haven't accuratly checked pulse width myself , but 6666 rekons it is between 18uS MIN to 183uS MAX ,
with the 10k pot and the 1k fixed resistor ,

on maximum pulse width with above coil and 200Hz i'm getting 270mA power usage (sound off) for test ,

on this i get , reaction to ground and my hand , interferance , and falsing , and "sound creep" ,
generaly a pain to use , and i wondered what had changed , why it was suddenly doing this ,

then i remembered , when i first started using this detector , i set the pulse width so that power use was a nominal
200mA , compromise between battery life and depth , not sure accuratley what the pulse width is at the moment but , at a guess based on turns back from max i would say it's around 160uS ,

so here's the thing , i once read on geo about soil saturation with to much power , where too much power can "flood" the ground and kill target signals , could to much power also "create" false signals ?

BUT , here is the funny thing , whilst testing "in air" , it also plays up when on full power / max pulse width (183uS)

so that's the puzzle i'm faced with , 270mA and she is a pig to use ,
200mA and she is stable'ish , and nice to use , weather in air or in the field .

is there such a thing as over powering a coil of a certain uH or wire diameter ?

all very strange that an extra 70mA makes all this happen.

any expert feedback or good educated guess's very welcome .

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	Re: Another P.I. link « Reply #169 on: September 20, 2011, 02:09:01 pm »

	Quote:	Posted by DOOLEY1972
is there such a thing as over powering a coil of a certain uH or wire diameter ?

When a coil is overpowered, it heats up a few degrees causing microscopic flexing of the coil. This flexing can detune the coil somewhat and cause instability. This was a common problem in the early days of radio and coils in high powered devices, like TV sets, are always coated with lacquer after they have been wound. This doesn't eliminate the overheating but does stop the flexing a great deal.

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