Another P.I. link

DOOLEY1972

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	Re: Another P.I. link « Reply #30 on: August 12, 2011, 03:49:47 am »

hello 6666 ,

attatched pic of the TL071 that i did ,

thought about using a fet in place of the 4066 , but when i ran simulations i found a small amount of voltage was being passed through the fet and being added to the output when "on", and when "off" i found a small voltage was "leaking" back through it from the sample hold cap.

but the 4066 seamed "ballanced" , it was neither adding to or taking away , so thats why i continued to use it.

yes , it is a waist of 3 of the switches isnt it , wonder if they make a single or a dual in an 8 pin package ??

hello xavier ,

have looked into the whole pic thing , nearly went out and purchased a ready made programer with usb / pc connection and software , may still do it yet , it would open up a whole new world of posibilities wouldn't it , as sometimes finding a solution round a problem using "discreats" can get complicated ,

oh , the inductance meter thing , found 2 on ebay , £12 gets me a meter with 10uH resalution and £35 gets a better meter with 1uH resalution , undiecided yet.

Posted on: August 12, 2011, 03:45:21 AM

hello 6666 ,

that scan didn't come out quite right , its cut off the end of the 1k from the TL071's + input , the 1k goes to the top rail , 15V , its clipped off the 1 infront of the 5. oops.

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6666

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	Re: Another P.I. link « Reply #31 on: August 12, 2011, 06:20:59 am »

Ok can you please cast an evil eye over this CONCEPT cct
I think I have drawn the changes correct, but needs checking
have added some notes, and things.

Ok on the fet, maybe a bit more experimenting
BTW i sorted out the diode thing between 7-6/2
cheers

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xavier

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	Re: Another P.I. link « Reply #32 on: August 12, 2011, 07:23:18 am »

What are you going to use for a power supply? 2 x 9V ? you will need to stipulate that in your schematic. Pin 1 of ne555 is not going to -15V but rather to ground. if possible use the coil inductance and coil size (makes things so much simpler) other than that it looks like the one that I sketched. Hope this will help you a bit.

All the best Xavier PS keep up the good work

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DOOLEY1972

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	Re: Another P.I. link « Reply #33 on: August 12, 2011, 09:11:39 am »

hello 6666 ,

that schematic is 100% as i did it , good luck and have fun , if you discover any good mods please post ,

hello xavier ,

for my power supply i used 8x1.2V AA 2500 mAH ni-mh cells , =19.2v total ,

i was originaly going to run detector on 16V , (MAX 18V for the 4066 and 555)

and the LM317 has to have 2V more than output , i plummed for 8 cells allowing 3.2V for the reg to "play with" ,

later reduced the regulator to 15V as the 555 osc was getting mildly warm , later found by experimenting 555's
get mildly warm even at 12V , so reg could go back to 16V.

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xavier

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	Re: Another P.I. link « Reply #34 on: August 12, 2011, 02:06:26 pm »

Hi Dooley

So then one could use two 9v batteries. Also what is the duration that you can use your detector? I would imagine that with 8 x 1.2v you would have a longer usage time than with two 9v. NE555 max voltage = 18v

All the best
Xavier

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DOOLEY1972

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	Re: Another P.I. link « Reply #35 on: August 12, 2011, 03:30:41 pm »

hello xavier ,

depending on pulse width and frequency depends on current draw ,

min freq (200hz) and max pulse duration it uses 250 ma , so with 2500 mAH batteries = 10 hours constant use.
max freq (400hz) and max pulse duration it uses 500 ma ,so with 2500 mAH batteries = 5 hours constant use.

think stardard 9v rect batteries @180ma will not be enough.

current can be reduced down to 50ma on min freq and min duration , but depth is poor .

at the moment im using it on min freq and max duration to get the best depth (40 cm for a 50p coin)
tried it on 1/2 duration and 125ma ,and allthough depth was less for same coin (30cm) was still not that bad.

this goes back to the whole 4 times the power to double the effect thing doesn't it.

but still think decent battery pack the way to go , they are a power hungry device , not like vlf's .
but then , a charge every night and she's fine for the next day , and if she's switched off for the digging process , dependant on hole size , she gets a rest.

oh , the 555 max voltage of 18v was listed as an absolute max voltage , the recomended voltage on the data sheet i read was 16v or below.

so kept on the safe side , didn't want to run anything at its limit and reduce life span .

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	Re: Another P.I. link « Reply #36 on: August 12, 2011, 04:43:58 pm »

Xavier
this is the pulse I am getting from the 555 pin 3
cheers

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DOOLEY1972

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	Re: Another P.I. link « Reply #37 on: August 12, 2011, 06:24:16 pm »

LOOKS NICE 6666

Posted on: August 12, 2011, 05:45:38 PM

hello 6666 ,
just noticed on your last schematic , pin 7 on the TL071 straight to + no 1k , other than that all ok.

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	Re: Another P.I. link « Reply #38 on: August 13, 2011, 12:13:09 am »

Dooley
Fixed up pin 7, thanks
can you please double check what you are doing with pin 3 on the tl071?
thanks

What should we nic name this beast ?

Posted on: August 12, 2011, 11:09:07 PM

hmmm I can see another problem
the numbering of the pins of the 741
are they two separate 741's ?

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DOOLEY1972

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	Re: Another P.I. link « Reply #39 on: August 13, 2011, 02:29:57 am »

hello 6666 ,

yes , the 741's are seperate , (7+)(4-)(6 out)(2 inv in -)(3 non inv in+) remaining pins open.

yes pin 3 on the TL071 correct.

regarding name , not sure we should rename it , only slightly modified from original blind squirrel by mike starcher ,

it think it would make us look bad to rename it ,

besides that , wondering if the guru's at geo are laughing at the mod's ,

only thing i can say , is that it works ,

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