TESORO GOLDEN SABRE

[ivconic]

No it is not secret at all!?
It is posted on very first page of this thread;

http://www.geotech1.com/forums/attachment.php?attachmentid=1977&d=1174874259

See?

[simonbaker]

Well...i respected original schematic...

(Oh no, not another secret schematic... !)

Maybe reason for it is because U107b is used for battery check, so needs to have supply not dependent on regulator?

Never stop learning lessons from good old TGSL...

Cheers,

-SB

[ivconic]

Well...i respected original schematic...

[simonbaker]

TGSL1265 last.lay

Hi Ivconic:

I am not sure, but maybe small mistake on TGSL1265 last.lay layout.

See attached photo. It looks like pin 8 of U107 (LM358 ) is connected to +12v instead of +8v.

Probably not important, but noise from speaker is on +12v.

Regards,

-SB

[fitos]

Hi,
Max.
So,TX sin is ok, p-p is ok.
You can see here TX/RX.Is this ok?
The coil disc good.Only sensitivity is poor.Why?Where I have to look for problems?
Thank you very much.

put new transistors j107 or bf245

[simonbaker]

[quote=Ultimate_Haze;91818]

Hi,
from what I see seems you have 190° phase out of RX vs TX. Ok... seems not bad at all... Tesoro's coils for uMax series have around 200° phase shift... that's cause you have about good discrimination.So that is about ok.

You have to check... if signal of RX shift to the left when you put near a target.
Yes when I put coin close to coil I can see that RX move left.

Also, another useful test is checking if coil is overbalanced or not. What do you see if you near silver there...? I mean is there initially a reduction in rx amplitude , then it starts to rise or just rise always ?
What do you mean?How to monitor the amplitude?
If I near silver coin to coil I see small voltage reduction in RX signal.Then quick increase and then the normal value there.0.375
/353 pin7/

You have also to measure rx voltage when no target at out of preamp.Do you mean pin7353 or across RX leads?..(form picture seems you have 300mVpp there but it's out of focus so I can't say for sure... but if so... gain is 43... so you have about 300mVpp/43=7mVpp nulled coil) then divide by gain to get actual nulled voltage... simple calculation required.
How I determinate gain value?

Why poor performance... ? Uhm... coil seems about good... maybe problem is at components... do you use different than good ones (e.g. LM308 and the like) ?

I have used LM308

Thanks for your attention.I now its slow progress with my poor skills.

With my prototype TGSL (not soldered) I only get about 20 cm on american quarter. Because I test inside house, there is much noise coming from coil. I know that because if I disconnect coil, noise much lower.

Just for information, a useful test is this -- put oscilloscope on about .1 cm/s, basically very slow.

Now look at output of each LM308. Dual trace is best if you have.

How does it look with no target signal. How big is noise? Move sensitivity control. Is there a point where the noise makes speaker beep, or is it always quiet?

Now wave target over coil and watch signal on scope. What is relative size of ground channel and disc channel signal?

If you play with disc control, you will see disc channel move in opposite direction from ground channel when you discriminate out the target.

I don't know why some people get more depth, they say it is due to coil. However, if your noise with no target is very low, it may mean you can increase the gain (or reduce the sensitivity threshold) to get deeper detection.

Cheers,

-SB

[Max]

[quote=Ultimate_Haze;91818]

Hi,
from what I see seems you have 190° phase out of RX vs TX. Ok... seems not bad at all... Tesoro's coils for uMax series have around 200° phase shift... that's cause you have about good discrimination.So that is about ok.

You have to check... if signal of RX shift to the left when you put near a target.
Yes when I put coin close to coil I can see that RX move left.

Also, another useful test is checking if coil is overbalanced or not. What do you see if you near silver there...? I mean is there initially a reduction in rx amplitude , then it starts to rise or just rise always ?
What do you mean?How to monitor the amplitude?
If I near silver coin to coil I see small voltage reduction in RX signal.Then quick increase and then the normal value there.0.375
/353 pin7/

You have also to measure rx voltage when no target at out of preamp.Do you mean pin7353 or across RX leads?..(form picture seems you have 300mVpp there but it's out of focus so I can't say for sure... but if so... gain is 43... so you have about 300mVpp/43=7mVpp nulled coil) then divide by gain to get actual nulled voltage... simple calculation required.
How I determinate gain value?

Why poor performance... ? Uhm... coil seems about good... maybe problem is at components... do you use different than good ones (e.g. LM308 and the like) ?

I have used LM308

Thanks for your attention.I now its slow progress with my poor skills.

Hi,
gain is from differential amplifier formula... R2/R1 stuff = R4/R3 = in our case 220K/5.1K = 43 (that's Vo/Vi)

The voltage decrease/increase you must look at rx signal... when silver target is still far you'll notice very small variation look carefully or increase gain at vertical section of scope, focus attention on peaks... see if they move and how , if increase or decrease when far.

Then near the target an look signal rise.

Kind regards,
Max

[Ultimate_Haze]

[quote=Max;91814]Hi,
from what I see seems you have 190° phase out of RX vs TX. Ok... seems not bad at all... Tesoro's coils for uMax series have around 200° phase shift... that's cause you have about good discrimination.So that is about ok.

You have to check... if signal of RX shift to the left when you put near a target.
Yes when I put coin close to coil I can see that RX move left.

Also, another useful test is checking if coil is overbalanced or not. What do you see if you near silver there...? I mean is there initially a reduction in rx amplitude , then it starts to rise or just rise always ?
What do you mean?How to monitor the amplitude?
If I near silver coin to coil I see small voltage reduction in RX signal.Then quick increase and then the normal value there.0.375
/353 pin7/

You have also to measure rx voltage when no target at out of preamp.Do you mean pin7353 or across RX leads?..(form picture seems you have 300mVpp there but it's out of focus so I can't say for sure... but if so... gain is 43... so you have about 300mVpp/43=7mVpp nulled coil) then divide by gain to get actual nulled voltage... simple calculation required.
How I determinate gain value?

Why poor performance... ? Uhm... coil seems about good... maybe problem is at components... do you use different than good ones (e.g. LM308 and the like) ?

I have used LM308

Thanks for your attention.I now its slow progress with my poor skills.

[Max]

Hi,
Max.
So,TX sin is ok, p-p is ok.
You can see here TX/RX.Is this ok?
The coil disc good.Only sensitivity is poor.Why?Where I have to look for problems?
Thank you very much.

Hi,
from what I see seems you have 190° phase out of RX vs TX. Ok... seems not bad at all... Tesoro's coils for uMax series have around 200° phase shift... that's cause you have about good discrimination.

You have to check... if signal of RX shift to the left when you put near a target.

Also, another useful test is checking if coil is overbalanced or not. What do you see if you near silver there...? I mean is there initially a reduction in rx amplitude , then it starts to rise or just rise always ?

You have also to measure rx voltage when no target at out of preamp...(form picture seems you have 300mVpp there but it's out of focus so I can't say for sure... but if so... gain is 43... so you have about 300mVpp/43=7mVpp nulled coil) then divide by gain to get actual nulled voltage... simple calculation required.

Why poor performance... ? Uhm... coil seems about good... maybe problem is at components... do you use different than good ones (e.g. LM308 and the like) ?

Kind regards,
Max

[Max]

Hi Ivconic and others:

Is BC547 special for audio circuit in TGSL, or would 2N2222 work OK too?

Regards,

-SB

Don't change much... same stuff I think.

[Ultimate_Haze]

Then use tx signal to trigger the scope (channel1) and get rx signal at output of preamp (on channel2): you'll spot the phase between tx and rx signal when no metal near... that's interesting measuring phase angle to know if your coil is made properly and you can disc the correct way...

Kind regards,
Max

Hi,
Max.
So,TX sin is ok, p-p is ok.
You can see here TX/RX.Is this ok?
The coil disc good.Only sensitivity is poor.Why?Where I have to look for problems?
Thank you very much.

[simonbaker]

audio transistors

Hi Ivconic and others:

Is BC547 special for audio circuit in TGSL, or would 2N2222 work OK too?

Regards,

-SB

[simonbaker]

Updated TGSL Final schematic with BD140 PNP

Here is updated schematic for the record.

Changes: TR3 BD140 transistor changed to PNP (was NPN).

-SB

[simonbaker]

I thought it was obvious from where i took that part..

Thanks, that explains it -- I knew circuit worked, but couldn't see why!

Thanks also for posting original circuit, it's useful to see it.

I will update the ".sch" ExpressPCB file that I uploaded before and upload it again with the PNP style transistor.

Cheers,

-SB

[ivconic]

Thanks for answers.

I don't want to bother you, but can you check the CScope schematic? Because it really looks like the collector and emitter should be interchanged, according to normal circuits.

I could not find any circuit (common base, common collector, common emitter) where the emitter points to the +V supply like that -- just looks like mistake ?

Cheers,

-SB

I thought it was obvious from where i took that part..