baracuda project questions

[sinclairuser]

yes dave your right about the scope i said all along in the barra thread that i was going to build now refine later back in july
as it was worth waiting to see a bloke i know in sept the only scope i would have bought was 110 pounds plus post so i thought sod that
this guy owes me a 2mtr145/70cm433 mobile set up and just happens to repair scopes and test equipment i called him and he can supply a proper one but is not up here till mid sept as others had built the barra without scopes i thought id have a go
also another bit of info relevent to our work came from this guy i asked him about inductance meters i told him i wanted to use it to build some coils for the barra and his exact words were ebay uk £13.99 philex clone l/c/r multimeter he said the company that is uk based is the one buy from as others post from hong kong and take eons!
anyway he teaches apparently as well and recomends this model for his students i asked if it was accurate and he replied better that the actual philex model mostly, some only as good as the original but ok for me and us so i bought one
http://www.ebay.co.uk/itm/LCR-RCL-IN...item3cbb2bec1f
and it works as with even some high end meters you must short the leads and take a base reading write that down and deduct it from the coil reading

as for the barra i have adjusted again and now can detect an 18ct ring
now better detection (currently 5" in air!)
as for the gold/silver leaf as of now the thin pad of silver leaves is detected a single leaf is not
the gold pad does not detect fully but it does give a reaction to the detector that with tweaking and practice can be usefull but as for silver a single gold leaf is not seen!
so have only enough wire to wind one more coil and cant decide which to try
testing with my ohm meter revels the silver about the same as alu foil and gold less alot
less my gut says silver my head hurts from thinking will probably try silver and report back
after all this pad of gold leaves weighs 4grams the silver 6grams(use it less) gold prices what they are it has to be considered thanks ally x
p.s. forgot to say the price on the meter has gone up since i got one in june but the above link is your choices the company i got mine from the units do not have philex logo(mine did'nt anyway) but the meter is the same

[bernte_one]

hello
i had the 4070L lcr meter too it work but not good for resistance measure
change the test tips for some better one
you can achive better result for small gold with plant coil
try 20cm outer dia inner hole 10cm with my litz i make 40-45windings
very short delay possible

regards

[satdaveuk]

Hi
Am I right thinking that the ICL7660CPAZ is ok to use as long as that 10v is not exceeded because looking at the spec sheets everything else is the same.
So the machine could either be used with 12V supply regulated down to 10v or run on a 9v supply.
Can anyone see of any problems with that please.

Regards

Dave

[satdaveuk]

Hi
Building off the layfiles that were kindly designed and then posted on here together with hand drawn circuit and taking note of the component part numbers and circuit ident seems to be plain sailing at the moment and like to say a big thankyou in advance.
The only thing im stumped on is where is the Sense pot that im led to believe was on the original Barracuda because for the life of me cannot see it listed anywhere.

Will post some pics soon of how its progressed

Warm regards

Dave

[sinclairuser]

as far as i know dave the pots on the original barra were threshold and delay in the rev2 board the delay pot is excluded and bridged as really once its set at the cemet pot to detect gold it does'nt need adjusting only very rarely i reinstated this pot on mine the two points on the board next to the delay cemet pot go one to pos1 and the other goes to wiper the same pot as threshold is fine
thanks ally x

[satdaveuk]

Thanks for the imformation Sinclair
I had my doubts because in the Andy Sabisch report he stated there were two external pots which were on/off sense, plus threshold, so theres me looking for something that isnt there.

Thanks again

Dave

[satdaveuk]

Almost done just waiting for the 25k presets once there installed shall solder the fly leads that go to various pots etc then clean and trim the PCB

[satdaveuk]

Can anyone tell me was the original Barracuda designed to work on 9v or 12v please ?

[homefire]

Looks like a Range.

[satdaveuk]

Thanks Homefire
Thats good actually if the data is correct on the revised circuit, because by the looks of the orignal picture here of battery cells looks like a 12v pack thats able to drop to 8.4v and still operate.
The minipulse anything below 1v drop off becomes unstable hense the cut off point that tells you to recharge battery.

[bernte_one]

hello satdeveuk

insted of 25k trimmer or potentiometer you can use 20k (more common type an cheaper so)
you can save the 5k at the end and with 20k you can adjust more precious

it tested in every case with offset trimmer/pot

regards

[satdaveuk]

hello satdeveuk

insted of 25k trimmer or potentiometer you can use 20k (more common type an cheaper so)
you can save the 5k at the end and with 20k you can adjust more precious

it tested in every case with offset trimmer/pot

regards

Thanks Bernte
So is that just a substitute drop in replacment of the offset trimmer or do we have to put a 5k resistor in series with it?

[maikl]

Thanks Homefire
Thats good actually if the data is correct on the revised circuit, because by the looks of the orignal picture here of battery cells looks like a 12v pack thats able to drop to 8.4v and still operate.
The minipulse anything below 1v drop off becomes unstable hense the cut off point that tells you to recharge battery.

I think the original Barracuda has 8x1.2V=9.6V, and stability is lost below 7.5V. I put 22K (I have not added 3K).

[satdaveuk]

I think the original Barracuda has 8x1.2V=9.6V, and stability is lost below 7.5V. I put 22K (I have not added 3K).

Thanks Maikl
Of course they are rechargeable hense the 9.6v, thats what im going to stick to, want everything as original as possible for my field experiments then can do mods if or when needed, thats good news thanks.

Maikl maybe you can answer this one that I asked earlier, Now we know that im going to be using maximum supply voltage of 9.6V, can you see any problem me using for U3 a 7660 instead of the 7660A.
Ive read the spec sheet till im blue in the face and cant see any difference at all apart from the supply voltage, unless im missing something.
Theres a good possibilty that the original used the 7760 because these machines had know access to install dry cells so the max supply could never have been over 10V.
If everybody here is not sure im going to try anyway and will post my findings in due course for fucture reference.

Regards

Dave

[maikl]

Hi satdaveuk.
You're probably already bought 7660 (max 10V), that will probably work. Maybe it's better if you bought 7660A... (max 13V), it is better to leave some reserves.
Is the original 7660? It is not known with certainty, tags are deleted, but it is not so important (except for the power supply).
It is important that what is said Alexismex: Q1=TIP127 and coil L=453uH R=1R5 (fast coil - similar coils Chemelec)
Otherwise, there are substitutes for 7660:
-3 times more expensive LT1054 (max 15V)
-2 times more expensive ICL7662 (max 20V)...