TESORO GOLDEN SABRE

[nelson]

Max, excellent expanation about what i m not an expert.
The only doub i still have is how to connect graphically the leads to null the coils.
I have read here that also if you dont have a scope you can get it with a multimiter. My scope is very small one, this is from radioshack and is connected to the pc, but i recognize that i m not very skilly with it.
This weekend i hope i can finally finish coils and test this golden sabre. My hopes are to work with for coinshooting and also to give a try on gold nuggets, but i know now that for gold nuggets i need a good coil. I also have to remember that this MD was build with TL081 instead of LM308, so i have to see his performance.
Ok, after i try all what you and Ivconic recomended to me , i ll tell you.
Best regards and thanks for your help.
Nelson

Hi Nelson,
you can't use resistor to get right value connected at pcb pads in a VLF. That way you lose current in your coils and add small instability due to resistor thermal variations, but most important you maybe can't get it oscillate on tx cause your impedance at coil could be wrong for stable operations.

NOTE:
You can use resistors e.g. in PIs detectors where you control the on switch by other timing circuits and so haven't a free running oscillator where the coil is a part of it; also in PI adding a series resistor to coil means cutting some current and so limiting battery drain, mosfet warming etc so in PI could be convenient having a resistor.

If you rewind with another thinner wire you have more inductance if other params remains the same, and also more resistance of winding.

As an example, do make a good DD with 22cm external diameter use that data:

wire from 0.25mm to 0.28mm external diameter ; you could use also 30AWG but but little mod on turns number are often required
I use :
TX 120 turns
RX 130 turns
resistance would be around 20 ohm , for both, or even more (22-24 ohm).

Good way to make coils is always wound about 10% more turns than extimated and then measure values reducing 1 or few turns step by step, till approaching what you need.

You could find more info about coplanar concentric in Emery's article, and info about tesoro's round conc coils on Mike's instructions (you can find in older threads about bandido and others)

You also need to null very well rx signal by moving on the overlapping area one or both coils. Use a scope, connect a 1k resistor and a capacitor like in rx stage in parallel with rx leads. You need reach under 3mV peak-to-peak, the lesser the better (I get 1mv pk-pk on my DD coil and works fine).

Having a too low resistance on e.g. tx coil in colpitts osc would mean have no oscillations at all or have with too hi distortion, so keep resistance hi enough to have good shape (perfect sinus) waves and stable operations.

Best regards,
Max

[Unregistered]

!!!!

Max Thanks,but why pain in the ***????
I told this is a site for begginers

[robert]

So...


Ok Unregistered, i excess with my comments from time to time. Sorry!
I am real p... in ...
You are right, this is forum for beginners, enthusiasts, hobbysts....Sorry again!
The fact is, you should download some comparsions charts for components or some software to install. ECA or similar. No need to persistently ask similar questions, post by post.
And for the last time, you should register!

[Max]

Max Thanks,but why pain in the ***????
I told this is a site for begginers

Hi,
no problem. Don't worry no pain, just a joke.
There are plenty of information about all that stuff in the Internet but sometimes you just need some hint by other people.

Some op. amps. are now also obsolete and that makes things a bit harder but for sure , if a solution exist, a replacement can be done, we'll find here.

And beginners are, of course, welcome.

That's why this forum exist I think.

Best regards,
Max

[robert]

....


OK just for unregistered, but this is last time!

[tiktak]

Hi

Not unregistred and not pain in the ***!Thats better.
I just wanna make as close as I can to the original.And when I read dont understand!I need someone to make it clear for me and then I understand!
Maybe you think that I am stupid,but I got more that you can imagine in my head!!!!!
And in the real world there are some substitues that cant be seen in the charts!!Thats HOW THE NEW IDEAS CAME!!!!!


UNREGISTRED is greateful for the shared information!

[Unregistered]

To nelson

Hi,
Did you test your detector?
What are the results with this changes?
Hope you acive good results!

[robert]

Welcome!


Welcome Tiktak! Yes, mostly you are right.But first you had to register and than i to admit this! I hope cahrts will help you.
Obey charts and dont worry, in 99% substitutions will work just fine.
regards!

[tiktak]

Hi

I have saw more that 3 fatal mistakes thanks to your advices!
So,this is the best way for me!
There is nothing more useful than expiriance!
So when you dont have it you have to ask someone who's been there already!
Thanks

[nelson]

To unregister, Ivconic, Max and all friends on the forum.

Today i finish coils:
TX coil is 101 turns, 0.25 mm wire, 5.6 mH, resistance 26.2 ohms.
RX coil is 107 turns, 0.25 mm wire, 6.45 mH, resistance 27.4 ohms.
Diameter of both coils is 19 cms.

The detector has all schematics components except LM308 that was replace by TL081.

TEST:
For testing purposes i place both coils on a wood table, overlap about 4 cms from each edges. The coils were connected to the MD with USB computer cable ( i removed both conector from it), this cable has 4 legs and shield.
I power the detector with 12 volts 4 amps batery.

RESULTS:

Operating frequency: 13.4 Khz
Sound: Low and steady. When turned on sound is very high and after a few seconds goes down.

Used elemets on test: 1.7 cms copper coin, 1.9 cms weeding gold ring, 4 inches nail, 1.2 cms zinc coin

The gold ring was detected at about 10 cms
1.7 cms coin detected at about 7 cms
1.2 cms coin 9 cms
Nail 6 cms

Results are very poor by now, may be the coils is to small or inductances are wrong

Discrimination works ok and only big iron elements are detected, not the smallest ones (nails).

Pingpointing is excellent

To inconic, can you help me on how to tune coils with a multimeter?
Do you think the problem can be inductances or diameter?

TL081 seems to work ok and i have not advice any problems with it.

Sorry for my english, but i hope this little report can by understand i be a help for anyone.

Regards
Nelson

Hi,
Did you test your detector?
What are the results with this changes?
Hope you acive good results!

[Max]

To unregister, Ivconic, Max and all friends on the forum.

Today i finish coils:
TX coil is 101 turns, 0.25 mm wire, 5.6 mH, resistance 26.2 ohms.
RX coil is 107 turns, 0.25 mm wire, 6.45 mH, resistance 27.4 ohms.
Diameter of both coils is 19 cms.

The detector has all schematics components except LM308 that was replace by TL081.

TEST:
For testing purposes i place both coils on a wood table, overlap about 4 cms from each edges. The coils were connected to the MD with USB computer cable ( i removed both conector from it), this cable has 4 legs and shield.
I power the detector with 12 volts 4 amps batery.

RESULTS:

Operating frequency: 13.4 Khz
Sound: Low and steady. When turned on sound is very high and after a few seconds goes down.

Used elemets on test: 1.7 cms copper coin, 1.9 cms weeding gold ring, 4 inches nail, 1.2 cms zinc coin

The gold ring was detected at about 10 cms
1.7 cms coin detected at about 7 cms
1.2 cms coin 9 cms
Nail 6 cms

Results are very poor by now, may be the coils is to small or inductances are wrong

Discrimination works ok and only big iron elements are detected, not the smallest ones (nails).

Pingpointing is excellent

To inconic, can you help me on how to tune coils with a multimeter?
Do you think the problem can be inductances or diameter?

TL081 seems to work ok and i have not advice any problems with it.

Sorry for my english, but i hope this little report can by understand i be a help for anyone.

Regards
Nelson

Hi Nelson,
nice to ear it works. About performances I think the problem is in coil nulling and I can suggest you a way using a multimeter.

I've tested that just one time, cause I use scope for that thing, but maybe you could find description useful.

You need a good ac voltmeter, with 1mV sensitivity. Also an old good quality multimeter would be good for that purpose. Watch at internal resistor printed on the panel of the instrument. You need at least 20Kohm internal resistance for cc and at least 4Kohm resistance for ac measures.
There are many that have 40Kohm/V in ac or even more.
The higher the better. You could use also a digital multimeter with true RMS in ac measures, but I suggest you start with analog if you own a good one. Sometimes digital meters have their troubles working with so smaller signals in ac , much depends on internal adc speed etc. so use as second choice and only with hi-brand products like lafayette, hc, etc

OK. you need a resistor load on rx coil leads (1kohm to 10kohm would be ok) and a suitable capacitance like you have in the circuit. You just need a perfect sine signal on rx at tx freq. and to minimize it as low as you can.

With that configuration connect the ac mvoltmeter and read , then moving slowly rx coil (or tx coil or both) try to keep signal low, to find point of minimum. You must reach under 3mV pk-pk that means about 2.12mv value on your ac scale. If you can stay under 1mV and your coil will be ok.

Another good test is reversing rx lead that go to circuit, cause signal must be in phase to get maximum sens and right disc, I've that behaviour on bandido.

Best regards,
Max

[nelson]

Ok Max and thanks for your help.
One more question, should i have to place the resistor and capacitor in series to one lead or shoud i have to conected it to each leads in parallel?
Both coils has i understood must be of the circuit and the frequency injection should be conected to the rx coil leads. Where should i have to place the multimiter leads?
In advance thanks.
Regards
Nelson

Hi Nelson,
nice to ear it works. About performances I think the problem is in coil nulling and I can suggest you a way using a multimeter.

I've tested that just one time, cause I use scope for that thing, but maybe you could find description useful.

You need a good ac voltmeter, with 1mV sensitivity. Also an old good quality multimeter would be good for that purpose. Watch at internal resistor printed on the panel of the instrument. You need at least 20Kohm internal resistance for cc and at least 4Kohm resistance for ac measures.
There are many that have 40Kohm/V in ac or even more.
The higher the better. You could use also a digital multimeter with true RMS in ac measures, but I suggest you start with analog if you own a good one. Sometimes digital meters have their troubles working with so smaller signals in ac , much depends on internal adc speed etc. so use as second choice and only with hi-brand products like lafayette, hc, etc

OK. you need a resistor load on rx coil leads (1kohm to 10kohm would be ok) and a suitable capacitance like you have in the circuit. You just need a perfect sine signal on rx at tx freq. and to minimize it as low as you can.

With that configuration connect the ac mvoltmeter and read , then moving slowly rx coil (or tx coil or both) try to keep signal low, to find point of minimum. You must reach under 3mV pk-pk that means about 2.12mv value on your ac scale. If you can stay under 1mV and your coil will be ok.

Another good test is reversing rx lead that go to circuit, cause signal must be in phase to get maximum sens and right disc, I've that behaviour on bandido.

Best regards,
Max

[nelson]

Does anyone have the manual owners for Tesoro Golden Sabre?
Regards
Nelson

Ok Max and thanks for your help.
One more question, should i have to place the resistor and capacitor in series to one lead or shoud i have to conected it to each leads in parallel?
Both coils has i understood must be of the circuit and the frequency injection should be conected to the rx coil leads. Where should i have to place the multimiter leads?
In advance thanks.
Regards
Nelson

[Max]

Ok Max and thanks for your help.
One more question, should i have to place the resistor and capacitor in series to one lead or shoud i have to conected it to each leads in parallel?
Both coils has i understood must be of the circuit and the frequency injection should be conected to the rx coil leads. Where should i have to place the multimiter leads?
In advance thanks.
Regards
Nelson

Hi,
connect tx coil to osc circuit (pcb pads). This way you get the oscillating magnetic field be generated all around the tx coil.
Connect capacitor and resistor in parallel to rx leads, and then the voltmeter accross leads too.
Move to null as described. When find minimum fix the rx coil with tape etc in many point , then recheck and if necessary fix again.

When you read a small few mv voltage you can test performance, disconnecting capacitor and resistor and connecting rx coil leads to pcb.

Best regards,
Max

[nelson]

TO GET MORE CLEAR, DO YOU MEAN THIS CONFIGURATION SHOW ON THE PICTURE?

BEST REGARDS

NELSON

Hi,
connect tx coil to osc circuit (pcb pads). This way you get the oscillating magnetic field be generated all around the tx coil.
Connect capacitor and resistor in parallel to rx leads, and then the voltmeter accross leads too.
Move to null as described. When find minimum fix the rx coil with tape etc in many point , then recheck and if necessary fix again.

When you read a small few mv voltage you can test performance, disconnecting capacitor and resistor and connecting rx coil leads to pcb.

Best regards,
Max