TESORO GOLDEN SABRE

[ivconic]

...and yesterday i finished first device on this pcb...Tested..
What to say? I am affraid you wont beleive me and take me as lunatic, but 1e coin detects at 46cm in air!!! Cola can at 80cm, 10cm x 6cm Al plate at 80 cm... 2.5cm bronze roman coin at almost 50cm!!!
I didnt expected that!?
Yes, GEB is adjusted that well, it does not react at all on large ferrite rod, hotrock, roman clay...i tested it on every possible junk in my workshop. Discrimination also perfect. Large tweezers rejects totally, not a sound,at disc pot adjusted to "2"...
Coil i tested with is ordinary 27cm coil, i usually make for TGSL's...nothing special...
What else.. i put hi quality capacitors there; WIMA. J107 as usuall, 2N2907 as usuall (all resistor arround as usuall except 24K which couldnt find, so i put 22K)...
LM308H - metal case.
In chopper stage i put BC177 and BC107 in metal cases. Minus voltage is now -6.5 volts, not -6.2 volts as it was with other devices...
Detector is rock stabile up to Sense adjusted to "8". Over "8" to "10" (max.) it can chatter ocassionally, but very silent and mum chatters.
Moving coil and cable randomly, squeezing cable....not a sound, perfectly stabile....
So....
It is to early to abandon this project. i was thinking to start with something else (kind a tired of TGSL's, made over 26 pcs so far)...but...i will not!
This is shoving more potential than i ever expected.
Now modding audio makes a lot of sence!
I have doubts (somebody else gave me tip) that present setup with MPSA13 and speaker do act like a parasitic ballast in a way. It is very possible.
I already noticed direct relation between type of speaker and ocassionall chatters. Those are produced in latest stage of device, not coming from frontend for sure...!
So...i was thinking how to remove that ballast and figure out some type of relaxative audio? But how? Which one? Possible to involve some stronger FET or simillar...?
Need to be explored more...
I do suggest you to try this pcb...much less noise than on all others made so far!

BTW
here are photos of device..

[ivconic]

I designed new pcb for TGSL. It fits exactly to plastic enlcosure for Fisher 1265. Why i did this? Somebody from Bulgaria is making huge series of those enclosures from ABS plastic. It is cheap there....i think 5e per piece. So....
Enclosure problem is solved for good!

While drawing routes i tried to pay extreme attention on signal flows. So...this maybe not perfect but very descent.
Later i found out that missed 1K resistor connected after 220nF from LF353 output.Not an issue, could be easilly added after...

Here is file, enjoy!

P.S.
This is the second time i am posting it. First time was posted on other thread by mistake....

[Fred]

Hi! FRiEnD

Yes.
I used a foil tape because is very thin.
Regards

DIRCEU

Thanks
I used copper tape before but it was thick.Performances difference with and without shield were enormous.
Now i have thin copper and aluminium tape.
Good luck,
Fred.

[DIRCEU]

Hi Dirceu,
Thanks again for this good informations!
Did you use aluminium for coils shielding?

I will try this coil as soon as i can.
Regards,
Fred.

Hi! FRiEnD

Yes.
I used a foil tape because is very thin.
Regards

DIRCEU

[Fred]

Hi Dirceu,
Thanks again for this good informations!
Did you use aluminium for coils shielding?

I will try this coil as soon as i can.
Regards,
Fred.

[DIRCEU]

HI! to ALL

I made the new coil for TGS it's a omega coil.

Great omega circle(TR)

Resist = 20 ohms
perimeter = 93 cm
inductance = 6.63mH
Wire diam. = 0.32 mm (28AWG)
Coil ID = 23cm
TURNS = 101 T
SMALL CONTRA CIRCLE = 8.5cm diam.

Circle

Resist. = 18ohms
perimeter = 40 cm
Induct. = 6.03mH
Wire diam. = 0.25mm (30AWG)
Turns = 132 t
Coil ID = 11 cm

Small gold ring = 31 cm
nickel coin = 27cm
Bi-metal coin = 29 cm
Aluminium coke can = 87 cm.

The results are not optimal but ...good I think
Discrimination is OK!

Only for test I change the RX wires at PCB and the sensibility increased very much, but with noises and no GEB adjusts.
I LOVE OMEGA COILS.

DIRCEU

LT1008 should be good replacement for LM308, therefore LT1012 should replace 2 of LM308 put togather in this schematic...noted as TL082....
I tested TL081 and later TL082 and those working erratic, producing to many "blah,blah..." in speaker when Sensitivity pot is over 50%.... Bad choice....
Also tested: 741,LM318,CA3130,CA3140,1458,4558,LM301,LM311,NE55 34.....
None of those can replace LM308 in this design!
Interesting was playing with CA3130; depth was much greater than with LM308....over 40%....but works erratically when no target in coil proximity???
It should be reconsidered, might CA....be used with some surrounding components changed...? I am to tired of experimenting, also have 8 Goldy pcb's to finish these days...so i let you, guys to check CA3134/40.....
Regards!

You can try OP07. Very close to LM308 except higher current draw from supply.

[ivconic]

Even DD coil can be made to pinpoint good. How..?
Well.... need to be arranged in different manner.
Preparing "D" shape for windings you must consider and plan more "sharper" overlaping area. Ovelap area must be almost rectangular without curvatures. Later when balancing those you will come to position where coils are nulled very well and overlaping area is pretty narrow and rectangular.
That kind of coil will cover much narrowed area of soil - logically would be more suitable for pinpointing. Yet...drawback would be exactly in that narrow area of detection, so it would be possible to miss some burried item if swinging coil fast and wide... Choose your preferences, or make 2 DD coils. One standard, with "eliptical" ovelaping and one PP with rectangular overlaping. Or...make smaller cc coil...
Regards!

[Qiaozhi]

Hi qiaozhi,
I use 25cm DD coil.

DD is not very good for pinpointing.
If you can find a factory-made Tesoro concentric coil, then buy it.
The pinpointing ability of the Tesoro web coils is excellent.
Alternatively you could make an omega coil. Dirceu has recently made one, and reports good results. The omega coil is also good for pinpointing.
Personally I wouldn't recommend building a concentric coil. It's possible, but very difficult.

[zzy]

Hi qiaozhi,
I use 25cm DD coil.

[Qiaozhi]

I made TGS,It's a motion machine.

The pinpoint is very very bad.

To find a small object is not easy.

In all metal mod,the pinpoint is a little improve.

What type of coil did you use?

[zzy]

I made TGS,It's a motion machine.

The pinpoint is very very bad.

To find a small object is not easy.

In all metal mod,the pinpoint is a little improve.

[DIRCEU]

Hi Dirceu,
If when you build your next coil - please could you count the number of turns? This would be very useful information for anyone wanting to make a copy.
Thanks.

To QIAOZHI

I will make this.

Regards

DIRCEU

[Fred]

That is a nice looking coil. What did you mount it on?

It´s a CRT monitor support (foot).
Wery strong and stiff but a bit heavy.
Fred.

[simonbaker]

Hi Max,
I'v just finished my First DD coil but i'm not sure about the it. 2cm coin could be detected at 25cm in air and 2.8cm at 30cm. What could be expected for the showing coins in the picture. Can you advise please.
Hardi

23.5 DD coil

That is a nice looking coil. What did you mount it on?