Another P.I. link

6666

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	Re: Another P.I. link « Reply #140 on: September 09, 2011, 09:04:53 pm »

Hi Mr X
I am building this MD to see whats going on but as far as the 4066 goes
the original cct is a bit weird but this is how dooley has it wired
according to his description.
cheers
6666

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6666

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	Re: Another P.I. link « Reply #141 on: September 10, 2011, 01:23:10 am »

Well so far so good, I dont like these temporary bread board things but it works
anyhow lets see if I can get these pictures working

I have only built the timing cct so far, but it works
the 555 is running at about 600hz

only using a small battery for testing

I cannot remember the exact width of the tx pulse but I think it was about 175uS.
The width of the sample pulse can go from zero to about 75uS
and the delay of the pulse can go from zero to about 75uS .

The first one is Tp1
2nd just the bench shot
3rd TP2
4th TPs 1 and 2
5th the delay between the TP's, different timing on the cro to show detail
6th My untidy bench

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xavier

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	Re: Another P.I. link « Reply #142 on: September 10, 2011, 04:14:27 am »

Well I'm busy making a new board should see by tonight if there is reason to go nuts or not Grin

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6666

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	Re: Another P.I. link « Reply #143 on: September 10, 2011, 04:39:09 pm »

Hi Xavier
I have made up to the first TL071
but I am getting strange voltage drops
around the bread board, so I think I will have to
go to vero board which will mean a delay
I hope you get your new pcb working
what process do you use for making pcb's ?

the laser printer hot iron transfer method ?

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	Re: Another P.I. link « Reply #144 on: September 10, 2011, 05:02:21 pm »

Hi 6666

I use positive20 photo sensitive spray ten I make two prints on tracing paper that I overlay after that it goes in the sun for two min then in caustic soda and after that in the acid. Well made the new board replaced all the components but still the same problem.

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DOOLEY1972

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	Re: Another P.I. link « Reply #145 on: September 10, 2011, 07:11:00 pm »

hello all ,

1.30am here , eyes tierd , i'm facing problems aswell ,

xavier , regarding the 4066 , just picked a switch that lined up with my vero board for ease , and all other pins that are unused must be earthed to stop interferance .

got the red green led idea working , lm741 was not sensitive enough , detector beeped before the led's changed , so used a TL071 (again) more sensitive to small changes , but not strong enough to drive big 10mm led's , so piggy backed 2 together , works a treat .

also added an external trim pot to "tweek" the center ballance of the offset on the first op-amp just in case bad ground moves the center point of the red green , also works well ,

but , audio quality , for some reason is now scratchy , replaced the audio 555 and npn , swopped the last op-amp ,
quality of audio still scratchy , oh well , supose i will find it , eventualy , wondering if it's just the internal mylar speaker ive fitted ,

oh ,swopped the last 741 for a , yes you guessed it a TL071 , more sensitive to changes , getting an extra 2 inches on a coin now , and before you ask i don't work for texas or have shares in them. Grin

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DOOLEY1972

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	Re: Another P.I. link « Reply #146 on: September 11, 2011, 04:22:05 am »

hello 6666 ,

i don't like breadboards either , i have one , never used it , it's either vero board for me for perminent jobs ,
or for testing i just lay the bits out and solder direct just for testing , but that's messy.

600Hz from 555 is quite high , power use of final detector if pulse duration about 165uS will be about 600 mA ish ,
on this design not allot to be gained with a higher frequency ,
i tried 100Hz ,200Hz and 400Hz
100Hz didn't respond quick enough during sweep
200Hz responds ok , and power use is ok , around 200mA to 250mA
400Hz didn't notice any inprovement in responce and she used about 500mA
so settled for 200Hz , a nice compromize between power use and responding during sweep ,

slight modification to the resistor from the first op-amp to the 4066 , was a 10k , was a little slow at changing the
stored voltage , tried 1K but it loads the op-amp a little to much , could see decay deforming on scope ,
settled for a 2.2K , able to alter hold cap quickly without loading op-amp to much ,
oh , use 2 sepperate 2.2K's to feed the 4066 if doing the dual channel modification.

width of sample and delay , original design used 25K pots , but 10K is all thats needed for width pot , this gives max 22uS sample time ,

hello xavier ,
different way of making boards , never heard of that way , but your results speak for themselves ,very tidy
result , never seen "photo sensitive spray" but then never looked ,

still playing here also , audio poor , can't put my finger on what has changed .

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	Re: Another P.I. link « Reply #147 on: September 11, 2011, 05:33:59 am »

Does it sound like something is holding back the audio? Sensitive spray is quite expensive but then you can make 4m² of PCB and at the end of the day works out a lot cheaper than the transfer not to mention that you don't need a lazer printer. I ordered 50 UV led's to make a UV box, my proses don't work very well when there is no sun LOL . From the 071 pin 6 you could go to a MPSA14 to turn on your led possibly for the audio too. Any how I'm sure that you will get it all up and running very soon but I'm still toying with the idea of the voltage comparator for the ferrous no-ferrous led's I think that it would be more sensitive to change.

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	Re: Another P.I. link « Reply #148 on: September 11, 2011, 06:03:10 am »

A mercury vapour street lamp also does the number for pcb exposure Xavier, but the led option sounds good. Have you built and tested the led light box. Alos got the Flowcode which I'll ferret arround with to see what tutorials they have to get going as well, thanks for the suggestion. The last schematic for the Blind Squirrel is that the one your are all working off at present?

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DOOLEY1972

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	Re: Another P.I. link « Reply #149 on: September 11, 2011, 06:09:50 am »

hello xavier ,

UV led's very good idea , thought you were in OZ ? doesn't the sun always shine there ?

yes , voltage comparitor , used for what they were made for the poss answer ,

think my problem is interferance , poss 50Hz beating with the 200Hz of the MD , not sure ,
nice audio range using threshold until i plug the 4066 in , so poss that or the TL071 ,
or simple the coil picking up on AC mains , also have interferance showing on scope , about 100mV at the end of
the decay , time to get her outside , but it never did it before when in the house ,
been going round switching things off but not found it yet , poss internal in detector.

time for philosophy : if it was all easy and nothing went wrong , we wouldn't learn and have the same satisfaction when all goes well.

Posted on: September 11, 2011, 06:03:29 AM

hello machineman ,

weather the last posted schematic is a good'en is up for debate ,
it was how i did it , and mine works with a few problems still ,
but xavier having problems with it , unsure what the problem is at the moment ,

as soon as i get mine to my liking , i'll do my best to draw a schematic that's 100% , hopefully using pc for clarity.

Posted on: September 11, 2011, 06:07:07 AM

that's it then xavier , wait till dark and shinny up a lamp post ,

either that or wear thick rubber gloves and liberate one from someone elses street , Grin

no , theft and all that out of order , someone will sell e'm , power use ? wonder how much ?

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