BARACUDA-Legend-1

[Davor]

To be frank, I'm not at all into replacing real instruments with PC toys. Even a 50 year old Tektronix will survive every each one of them.

For example, I had a big pause in my electronics hobbies, and at time I had some completely different arrangements so I did not put much effort in buying a scope then. Just for argument sake, if I bought a PC toy oscilloscope then, I could not use it now with most of the nowadays computers for several reasons: parallel ports are not so common any more, floppies are quite uncommon, 8086 timing is quite uncommon nowadays, even with emulators and Mo'Slo.
If I bought a 20 year old Tektronix instead, it would have been 30+ ish Tektronix now, and in mint condition too.

See the difference?

I can live with a PC toy that is already there, like a soundcard. Unfortunately these are a no solution for PI

[satdaveuk]

Add on module for Laptop

[QUOTE=Davor;159072]Soundcard ADC is far too slow for PI Davor... Is there a add on ADC module that can be pluged into say the serial port, wondering now if theres a project out there to build one, Now that would be a good worthwhile project to build for everyone on here, Davor.. we all know your a clever man, Im proposing to you to Design a simple as possible project to add on to serial port to give us the scope we require.
I say serial port because all the nessary inputs are all there waiting for you, I know the modern laptops dont have them, but theres no problem with that as you can buy old laptops cheap as soggy chips, which is good news for those who will need to aquire one, and if any spares are required for them they are also cheap.
Just upgrading my old Toshiba laptop which my mrs gave me, needed a new wireless G adaptor, also wanted USB 2.0 ports instead of 1.0 so bought PCMA Type11 module, which slides into the common unused slot on the older laptops, the whole lot brand new from a dealer in H/K I deal with cost me just over £10 incl p/p, Also IDE hard drives which any laptop over 5 years has one go quite cheap, so its happy days for everyone. All we need now is your expert attention on a simple scope project to add onto are already cheap laptop.
This is a very important must do project and needs more attention than anything else for those who dont have a scope, because without a scope you cant produce a successfully built metal detector project unless your very lucky.
Warm regards

[satdaveuk]

I been also searching the net for a proven add on scope module that can be pluged into my laptop for doing onsite field tests with MDs projects, there out there know doubt but with a £ssss price tag.
Will bring that subject up on the apropriate forum here see what others have done.
Either that or if my calscope is in fact beyond repair im going to have to purchase another one anyway due to my work, so will be looking at mains/battery type, which is not a problem these day since the Lcd has taken over from the CRT less current, more practical, lots have that option now.

[Davor]

Soundcard ADC is far too slow for PI

I'd be playing with PI already if only I have a working scope. Still seeking. Not in mood for spending food money on it.

[satdaveuk]

Could be FET Q5 in motion/non-motion circuitry. It may have Vgso quite high so it leaks. Just replace it with BF245A or B.

Thanks Davor shall look into that one, also my build is hyper sensitve im for ever having to tweek the front controls because there so touchy as in happy medium between full tone and low threshold.
Its not the batterys because they were fully charged, i really need to get my scope back into service its like walking up a blind alley, im so used to using a scope even down to measuring voltage rather than pick up the avo that i feel my hands have been choped off.
Anyone used that latest pc scope software from july last year that uses the sound card? ive put it on the lap top, what a improvement since 1997 with the scope 30, maybe can use that as a make shift, trouble is only goes up to 1 volt so would need to make some antenuated probs up will need to put in some sort of varibal to calibrate correctly, that can all be done at the plug end, any ideas on what components to use on them? , cause dont want to knacker the laptop, also will be a bit of fun to see what this software can really do.

[satdaveuk]

Yes in this way , with the Tip 127 you have a notifiable audio tone very little but it exist ...so with practice ... your brain in the field has something to use for discrimination .... like in the early Vlf detector you can feel what you have detecting

And to add to that the difference is more noticeable when using the original coil spec 7.5" inner 8" outer compared to a 10" coil, Although I need to do more experiments its looking like keep everything to as near spec as possible like the TIP127 is complimenting the original coil specs.
When people were having problems getting spares from Anchor the dealers were fitting surf PI coils to them which worked very well far as depth but there were lots of customer later complaining that although the depth was increased it decreased the solid tones to the washed out sounds of non coloured metals also it made pinpointing diffecult which is identical to the symptoms of my two coil builds.
That chap who originaly designed the Barracuda was a metal detectorist and had been for many years he spent alot of time designing before production started and its turned out everything he said it would be, everything was hand built as we do here, he couldnt supplie enough for the market, the word got around and took off alot faster and he just was geared to produce enough to even give a spares back up service, and thats why he wouldnt export outside the states , its just sad he hadnt been so good with his business side of things otherwise he may have been rubbing shoulders with the likes of ML, Whites etc.
The success of the actual design was all down to build and keeping components to a very tight spec which takes time as most of us know on here by experience.
Changing the subject my delay and threshold are very touchy and im having to adjust alot, was in open field lunch time away from power lines etc, is anybody else experincing that? or is it just me.
Regards

[Alexismex]

Yes in this way , with the Tip 127 you have a notifiable audio tone very little but it exist ...so with practice ... your brain in the field has something to use for discrimination .... like in the early Vlf detector you can feel what you have detecting

[6666]

Hi Alexis and satdaveuk
let me get this correct about what you are saying,

if you use a tip127 you get noticeably different audio tones when detecting iron and other non ferrous metals
but when you use a fet these differences are less ?
cheers
6666

[Davor]

The only thing I dont quite understand is my build is running non motion, can anyone explain why that maybe? Im not complaining because prefer it that way, just wondering why.

Could be FET Q5 in motion/non-motion circuitry. It may have Vgso quite high so it leaks. Just replace it with BF245A or B.

[Alexismex]

It is good to see result , yes Barracuda is a nice detector with this little difference between iron and colored metals , thank to the slow response of the TIP27...because if you use a Mosfet you do not have this effect , it is good also to see this old design still competitive today ...bravo Satdaveuk to accomplish your work and to give to another people this positive response
Alexis.

[Qiaozhi]

... its not much bigger than a "fag" packet,

For our non-English readers, that means a "cigarrette" packet.

[satdaveuk]

Hi
A very big thank you to Alexismex and Apberg
Finished the Barracuda working from Alexismex hand drawn circuit and Apberg lay files and what a nice bit of kit, to be honest its works better than I exspected considering that ive not got round to repairing my scope, made two coils one as original 7.5" form 8" outer, and a 10" form which comes in at 10.5" outer which i used larger dia wire.
Connected the 10" up just now in the workshop hanging from the roof thats still wet with varnish after wrapping with hospital bandage connected to a 2 meter mic cable measuring from plug 1.2ohms 560uh, just twiddled the offset and the delay, with the original 330ohms damper and getting 2'6" from a small petrol lighter refill, 1 meter from a motor bike side panel, 9" loud and clear with a 22ct gold cuff link, and 7" with a modern 20p coin.
Unlike the 10" coil using the 7.5" theres a very distinct difference between iron and coloured metals, the non ferious is a loud crisp clear cut sound where as the iron is clouded.
The quick test ive done were all in the workshop so doesnt mean jack pooh really, in the next few weeks will give it a good thrashing and let you know the outcome
Im quite shocked really, once I get this set up correctly with a scope its going to out perform the Minipulse 3. Ive built a housing for it nothing flashy its not much bigger than a fag packet, so its going to be dead handy.
All components were checked for spec before installing and apart from the 6,800mfd electro cap everything else is the same as the hand drawing although i did fit the extra delay preset on board where as the original Barracuda didnt have one.
Also didnt match the FETS, maybe I was just lucky or maybe there not ment to be your guess is as good as mine.
The standard 7760 works fine and runs cold with the 8 rechargable batterys (9.8v) and although ive mounted the TIP27 on a small heat sink it didnt need it as that also runs cold so all in all its happy days.
The only thing I dont quite understand is my build is running non motion, can anyone explain why that maybe? Im not complaining because prefer it that way, just wondering why.

Thanks again for a very worth while project, its so good and simple going to build another one for my sister .
Will post pictures etc when time permits.
All the best from a very happy Dave
Back to school with Samsung tomorow in London so need to try and sleep now.

[maikl]

Qiaozhi thanks for the explanation.

[Qiaozhi]

Does this mean that Goldscan, TDI ... are not PI detectors, or do not discriminate?

The Goldscan and the TDI are PI detectors that incorporate a method for ground balancing. By adjusting the ground balance control it is also possible to discriminate against targets with a given time constant. In other words, you are simply moving the ground notch to a longer delay setting. This is not the same as the discrimination you get with a VLF. If you adjust the GB control to eliminate a certain size of nail, then larger or smaller nails will still be detected. This is target conductivity discrimination, and not ferrous / non-ferrous.

[maikl]

The Barracuda is a pulse induction detector and therefore cannot discriminate between different metals.

Does this mean that Goldscan, TDI ... are not PI detectors, or do not discriminate?