TESORO GOLDEN SABRE

[Max]

Hi,

FOR Tiktak:

Have we to split hairs here ?
If he said that's 1cm diameter that's so. Maybe is an older coin.


For Ivconic:

got an idea... to get a better sound:

- do you see the 22nF cap that is on pin5 of last LM358, just after the 1n4148 diode ?
my thought was that if I'll change its value to e.g. 1nF I'll get a better audio response and faster response of detector.
I've made and seems it works: got a better audio detection at maximum depth (about 27cm for 1eur coin); some instability only in all-metal mode.

It's not a big mod but I'm satisfied of sound response at maximum depth now, seems more consistent sound.
I think that with headphones I don't miss deeper targets this way.

If you have time try the little mod.

Best regards,
Max

[erolunall]

detection range TGS

Hello all

I wonder TGS detection range for big metal object for example car or 1 m iron object and I want to ask to ivconic secret of his succes on TGS)
thanks
Erol Ünal

[tiktak]

Hi,

Hi,
Max.
Ok,ok!
Just wanned to know for shore!You say that 38 cm for a dime is not posible.
But 1 cm is dime size.

Nice simple mode I will try this 1n !
Just to tell that now I have found LF353P!!!!At last.
Now my components are 100% same as original.
And the last thing to do is good coil!
And NE566N what do you think is this make differance in audio.Ivconic tell that he search for another solution!This mean that its not so good modification.

[Max]

Hi,
Max.
Ok,ok!
Just wanned to know for shore!You say that 38 cm for a dime is not posible.
But 1 cm is dime size.

Nice simple mode I will try this 1n !
Just to tell that now I have found LF353P!!!!At last.
Now my components are 100% same as original.
And the last thing to do is good coil!
And NE566N what do you think is this make differance in audio.Ivconic tell that he search for another solution!This mean that its not so good modification.

Hi,
I never said that e.g. detection of 1cm diameter coin is impossible at 38cm.
I just said that you need a larger diameter coil (e.g. 28cm or more) and a very well done tuning... but as Ivconic right stated you'll have a difficault pinpointing respect to e.g. 22cm diameter and also much more geb problems.

For sure is impossible with a DD22 coil, at least with a small power VLF like GSabre is... no dubt about that.

I think that 566 is good for vco, but problem is that if you have no more informations of e.g. metal type by audio is almost unuseful having the vco, if not for e.g. evaluating the strenght of signal, thing that you already have in original GSabre.

VCO option could be very interesting if the disc informations could determine different frequencies for different metals (multi-tone id).

Kind regards,
Max

[Leto]

amplifiers..

Hello Max and others..

do not know about TBA820's but I'm very much satisfied with old lm388 - it works perfect. I connected it after C517 with 2k resistor it does just what's wanted: amplifies for 8ohm impendance speakers. Input resistor is really needed (or the amp. input is overloaded) maybe also lower gain transistor in place of C517 would be OK.
Higher consumption could be a problem for someone (10-15ma) but personally I do not use 9v batteries for long time now.

[Leto]

VCO

Originally Posted by Max
About tones... I think the way one could wire such a mod. is related to the 2 channel informations:
watching at voltages of the 2 lm308 outputs is the key to get multiple tones.
One could also use outputs of comparators near the sens pot.

When iron is present channel output voltages are in oppositions, thus giving zero effect on output. When coloured metal is present, instead, channels have similar behaviour.
That way is possible making a multitone information.

Problem is that if you vary disc pot setting you'll vary also audio response, and that's no good, confusing the user. So a real mod. must be place disc pot as trimpot with minimum setting, then leave the user just ear the sound difference to disc stuff, not moving the pot (as in original GSabre design).

Max very good idea to take audio input at 308 outputs. To avoid disc. pot problem it could be possible to add one channel only for multitone sound or use simply notch channell.

For further buffer I found following shematic interesting (posted by rumenisat on md4u.ru-forum) It's purpose is: colour metal identification with RGB LED - kind of a VDI. It could be used also for trigger of two audio oscillators with mixer to produce audio multitone ID.

[Hush]

What the hell...

Ohhh..
I am in big trouble!
I spend all bloody day to wind coil, wind by wind, without any crossing of wires.I've used Chemelec inductance calculator and got results:
For 10 inch inside diameter coil (256mm) - O concetric coil
coil lenght: 0.2 inch (5mm)
wire diameter: 30 AWG or 0.27 mm with varnish
turns:117
inductance:7.1mH
I think that calculator is very, very good .
Everything looks fantastic, but no, no my friends! My freaky multimetar "told"
me the coil inductance isn't 7.1 mH (that should be RX coil), but 9.8 mH!

Let's say y is specific resistance (I haven't that bloody letter).

R=y x l/S then l=R x S/y

y for copper is 0.0172 ohm x mm2/m
resistance of my coil is 33 ohm

S=r2 x 3.14 ( I haven't bloody pi too) S=0.125 2 x3.14=0.0491 mm2
l=33 x 0.0491/0.0172 l=94 m

So, wire lenght of my coil is 94 m.

let's calculate on other way:
O=2 x r x 3.14 O=0.256 x 3.14=0.8 m

0.8 x 117 turns= 94 m - the same results.
So what, you can say, but now I am sure the number of turns is correct-117
And what now? Should I trust to my multimetar , it looks good, think it isn't from China, but who knows? Or should trust Chelmec?
Immediatly need help... help... help...
Yours Hush

[Geo]

Check your multimeter ......

[Hush]

Hi Geo! Nice to see you again. It is new multimeter.Check it, how?

[Geo]

Hi Hush
Only if you have a standard induction . Another way is to give at a coil a AC voltage and to measure the voltage across the coil and the current who flow through the coil. Z=U/I and if the freq is high then the Z is very close to Xl. Xl=2*pi*L....... L= Xl/2*pi

(Z is the total resistance and Xl is the induction resistance). If the multimeter is OK then the L will be close to the multimeter reading.
Good luck

[ApBerg]

Hello Hush.

Think you want to make a open centre coil ?
Look at post no: 22. I made some opencentre coils, works well.
For the 25 cm coil the 117 turns are to many.

You can connect your coil to the transmitter part from the goldensabre and look for the freq that is given , use for golden 15 nF cap, freq must be somewere 14 kHz, if lower freq then reduce the 117 turns
Good luck

Ap

[tiktak]

Hi

Hi,
Leto.
What kind of battery did you use?
And can you please tell me where to conect those ground points?
I wanna try your audio modification too.
The speaker is going in sane ground point as before,but where I should conect others?
What coil did you use with your TGS?

[Max]

Ohhh..
I am in big trouble!
I spend all bloody day to wind coil, wind by wind, without any crossing of wires.I've used Chemelec inductance calculator and got results:
For 10 inch inside diameter coil (256mm) - O concetric coil
coil lenght: 0.2 inch (5mm)
wire diameter: 30 AWG or 0.27 mm with varnish
turns:117
inductance:7.1mH
I think that calculator is very, very good .
Everything looks fantastic, but no, no my friends! My freaky multimetar "told"
me the coil inductance isn't 7.1 mH (that should be RX coil), but 9.8 mH!

Let's say y is specific resistance (I haven't that bloody letter).

R=y x l/S then l=R x S/y

y for copper is 0.0172 ohm x mm2/m
resistance of my coil is 33 ohm

S=r2 x 3.14 ( I haven't bloody pi too) S=0.125 2 x3.14=0.0491 mm2
l=33 x 0.0491/0.0172 l=94 m

So, wire lenght of my coil is 94 m.

let's calculate on other way:
O=2 x r x 3.14 O=0.256 x 3.14=0.8 m

0.8 x 117 turns= 94 m - the same results.
So what, you can say, but now I am sure the number of turns is correct-117
And what now? Should I trust to my multimetar , it looks good, think it isn't from China, but who knows? Or should trust Chelmec?
Immediatly need help... help... help...
Yours Hush

Hi Hush,
sometimes happens you made a coil and then figure out the inductance is wrong from calculations, too many factors... even if you tight wire with tape you'll get an increase of inductance ! Not much but you can see it.
Sometimes is just LCR meter/multimeter that gives you strange numbers and you can't trust if not hi-quality device.

So what to do ?

1. follow ApBerg advices, he knows many things about GSabre, so he pointed you in the right direction

2. no need of too many calculations... make say 15% more turns than expected... then cut them away till reach your operative frequency (I got 14.35 KHz with GSabre , but my coil was developed for BandidoII, it's the same) Think that original freq. would be a bit over 14KHz, if remember well.

3. make then RX and a good null as explained before many times

4. shield as explained

5. test before sealing

6. seal and package the coil for real use

7. test on field (and cross fingers)

Best regards,
Max

PS: I have a device that use to test coils too... is a general purpose free oscillator (from few khz to 300Mhz I think) but cannot find schematic.
When use it I just put coil and a parallel cap, like in rx section... then measure osc frequency live !

It's a good thing cause it always oscillate !

If I'll find schematic I'll post it. It's easy to made.

[tiktak]

Hi,

Hi,
Max.
You have advice me to try use 10 NiMh cells (1.2volts each) 700mA/h or more for TGS.But in shop they ask me which size?So which size is best?
And can I recharge them with AC/DC adapter?

[Max]

Hello Max and others..

do not know about TBA820's but I'm very much satisfied with old lm388 - it works perfect. I connected it after C517 with 2k resistor it does just what's wanted: amplifies for 8ohm impendance speakers. Input resistor is really needed (or the amp. input is overloaded) maybe also lower gain transistor in place of C517 would be OK.

Higher consumption could be a problem for someone (10-15ma) but personally I do not use 9v batteries for long time now.

Hi Leto,
thanks for schematic. I've made with TBA820M and if connected like your (voltage splitter after c517) works really good, loud audio.

My problem was at first attempt cause I connected before c517... and there are voltages and impedance problems there.

TBA820M uses only 4mA when no sound... then consumption increase cause of sound to much more... it gives about 2W power on 8ohm.

The VID mod is really interesting, could be used to make a real useful multitone id.

I'll test it soon.

Thanks again,
Max