TESORO GOLDEN SABRE

[ivconic]

Generally you lose a lot of things at e-bay .

But my friend i can't help you. We are very small in order to resolve such issues
Anyway my regards
Btw... i want to make a OOcoil 20+20cm. Who is your opinion????

It will be deep! And i mean very deep! But as Max noted;y you should take special measures dealing with Faraday cage there..Must make hi-quality f.c....Personally i'' avoid Al foil in larger coils. I'll try some conductive material to obrain like graphite or simillar..There is certain skin effect occured when Al foil is used.Huge drawback! So, Al foil is suitable only for smaller diamm.coils...Another thing; less space between wires and foil - better. I am not usin any more scotch tape in between. When coil is wounded, next thing is to wind Al foil over it without anything in between.
20cm OO...good to try! If 0.25mm is used than you should start with 90 turns and measuring inductance try to adjust number of turns to achieve 6mH for TX ans 6.5mH for Rx...If 0.3mm is used than start with 120 turns...Do not pay to much of attention on resistances...If they are in range 17-25ohms than it will do the job. But do pay attention on inductances!
Bets regards!

[ivconic]

About nulling - balancing coils;

So far i made a lot of coils...Also experimented a lot...
Max can you repeat me your final measurements when your coil is nulled?
First is good to know that aint no multimeter with which we can accuratelly measure induced voltage on RX coil. Yes we can have some approx. results but not quite accurate...Why? Most of multimeters have good response on low frequencies, but on higher not! Error level rises up as frequency rising.
That's why oscilloscope is unreplaceable in accurate measurements..
But....in case we dont have osci.- must use what we have..Simply as that.
I do have quite useable multimeter with 200mV range AC/DC...So when finishing nullling coil i usually gain 0.000 mV...On first glance this sounds like a perfect balanced coil! But, as we know from experience...it is almost imposiblle to absolute balnce coils, due many objective reasons.
Above mentioned nulling is measured without 15nF parallel to RX coil. When i add that capacitor, induced voltage rises up to 0.009mv in most of cases. In few cases it raised up to 0.012mV...Than i triead again to fine readjust null to obtain absolute zero...yet without succes...Quite expectable.
But, somethimes i am to lunatic about those things...i want to push more and more, so today i made experiment with one coil. I nulled it with attached capacitor 15nF parallel to RX. Final voltage was 0.008mV...
I figured way how to achieve absolute zero; i put (carefully chosen) few very small pieces of Al foil inside coil housing, covering few spots on coils.Must mention those pieces are not connected anyhow in coil setup. Those pieces actually play role of "foreign body" inside coil. By moving them slowly,carefully inside coil i found exact spots and gained absolute zero balnced coils!!!
Actaully those Al pieces provoked minor induction, enough just to balance coil to zero.Coil is finished., filled with mass.Drained...and now is ready for terrain work. I checked it with detector.....PERFECT!!!! I gained extra 2cm's on single coin!!! Stabillity is good as it was before. Discrimination also good...
What to say? Crazy experiment gave me crazy result!!
Now i am thinking other thing; so i put Al pieces - "coloured" metal...What should be if i put iron pieces ("non-coloured") instead Al???
Only way to find out is to make another coil and try. I am planing to do that tomorrow...
I do know what is all about....perfectly clear to me. But i would like to hear your opinions...?
Heh,heh,heh...!

P.S.
You should appreciate this! I gave up one of "master secret" here!

[ivconic]

P.S.
You should appreciate this! I gave up one of "master secret" here!


When "secret" reach the public; it only means - new one is "cooking"...
Heh,heh,heh...
Very best regards!

[ivconic]

Oooh! I forgot to mention one imoprtant thing;
So i gained 0.000mV on coil with 15nF attached....
Well, just for any case, i later removed capacitor and measured again. Still 0.000mV on RX!!! Very good! Remained zero balanced!!! PERFECT!
Conclusion: capacitor only helped me to very fine readjust balance. No fakes at all from it.
One more thing;
Max suggested 1k resistor to be added when nulling....well, i must say that resistor absolutelly "sucked" any mV over zero...So it is faking - omit it!
Make double test; null coil with resistor and than remove it and measure induction....You will be amazed! Later remove even 15nF just to check are there any fakes or not..
Those 5K1 on LF353 inputs are more than sufficient there. I suggest to experiment with various values, starting from 3k3 and up..But this mostly dependes on op-amp used at front end..
Bye!

[ivconic]

"Oooh! I forgot to mention one imoprtant thing;..."

Oooh! I forgot to mention MOST IMPORTANT NEWS;
NO MORE OCASSIONALL CHATTERS AND BLEEPS on coil balanced this way...
He,he,he...!

[nelson]

Ok Max and thanks for information about TGSL push switch.

About Gold Bug. Thats ok, you are 100 % correct and i will try the voltage regulator.

Today i whent to a river side, to see how this gold bug is performing.
Grund balancing is very easy to do, all functions are very useful for what the detector is done. If you try to do some coing shooting with it, can by good, but not so good has TGS. Discriminatin is fix to avoid only ferrous metals. TGS can discriminate on a wide range of metals conductivity. So my gold bug, will be used only for gold. Also i noticed how good this machine is on getting some very tiny metals. For example i made an experiment checking a detection of a small needle head. This was detected underground at about 3 to 5 cms.
Ok Max thanks again.

Best regards

Nelson


[quote=Max;60505]

Hi Max.
Yestarday i began to build TGSL and i noticed a push buttom on schematics, do you know what is this for?
About my post about Fisher Gold Bug 2, i ll made the voltage regulator, but i will like to know from you, if the detector runs only from 9 volts or 18 volts.
For me, i understand that the machine works with 9 volts.
i hope you can understand what i mean.
Best regards.
Nelson




Hi Nelson,
I think you're referring to the switch that is at comparator near diode D12 is for inserting or not the 1Mohm resistor parallel to D12.

This will give you an audio boost... but if you read Ivconic's post about stability you'll notice there is a drawback in having that 1Mohm resistor there... cause of more instability at max sens.

So using the switch you can enable or disable the audio-boost, depending if your current setup (pot positions etc) can tolerate a bit more instability or not.

You can also avoid 1M and switch if you feel comfortable just with original audio. Is your choice.

About Gold Bug the voltage is 9V cause the 2 batteries feed the circuit by two diodes... so battery+diode are parallel one each other... they did that way cause circuit maybe require more current respect to that a single 9V can provide for enough searchtime. That way each battery provide about 1/2 current ...so last twice.

You have to check if your circuit is the same as in schematic I provided and then build a 9V regulator if so.

BTW the real voltage is under 9V depending on drop on diodes... it's something 8.3 to 8.5volts... but you can safely use 9V regulator for circuit.

Best regards,
Max

[Max]

Dear Max

We are fixing 1 k and 15N f to rx for nulling.
are we have to cut or solder 1 K AND 15 n to RX after Nulling.?

Regards
Erol

Hi Erol,
you need that components just to find null position and reading so the lowest voltage across them. After you fixed coils in that optimal position you'll disconnect rx leads from dummy load (resistor+capacitor) and connect to the PCB pads for RX as in schematic.

Another way to get similar result is connecting rx leads directly to PCB pads and nulling reading the lowest voltage at output of preamp. ic. : that way you don't need the external dummy load to null.

One way or another is your choice... both work for our purposes. I use dummy load cause I wanna read directly the voltage accross RX leads and (passive) load and compare with other readings I've made for other coils in the same way with same components, thus avoiding effects due to active device at preamp (in TGS is LF353) e.g. offset etc

Best regards,
Max

[Max]

"Oooh! I forgot to mention one imoprtant thing;..."

Oooh! I forgot to mention MOST IMPORTANT NEWS;
NO MORE OCASSIONALL CHATTERS AND BLEEPS on coil balanced this way...
He,he,he...!

Hi Ivconic,
my last reading on potted coil is about 5.5mVpp that is a bit more than I have when nulled first time. I think that little forces developed due to the epoxy reactions and hardening give me that deviation respect unpotted coil.

I read that with dummy load (1Kohm+15nF) and scope.

One thing to consider is that heat generation due to epoxy... the peak of temperature easy melt or make less heavy fixed the temporary fixings of TX and RX wounds on the housing... BTW my actual housing for this DD255x137 is not the best ...made of PVC plastic that you know is really sensitive to heat and can deformate due to its action.

Anyway, my very slow epoxy (the one for surfboards) revealed a maximum peak of 68 °C (70° C on specs) I've measured before sealing coil... so heat didn't damaged too much my coil null.

Coil sealed have now same performance as it unsealed... and I'm happy of that. Just I have to wait too much for epoxy end-reactions if have to make others. I've also made another DD22 same way.

About multimeters... and nulling, when you null without capacitor I guess you don't get a perfect sinus on RX leads but a disturbed signal (due maybe to e.g. 50Hz intermodulation and similar)...

If signal is not perfectly a sinus you'll get 0.000V on a digital multimeter very easy... cause they offer good readings only with sinus shaped signals... that's so cause of their internal ADC and circuit configuration... and also at higher frequencies you get still good readings if you have a perfect sinus signal but not on an arbitrary shaped one.

So I think that when you read 0.000v there's actually some magnitude but that your multimeter can't read properly , giving you zero on display.

Adding al foil pieces is like correcting overshots in PI coils with brass washer or similar... actually I think you'll underbalance coil that way... but you know that sometimes you'll gain better sens with a bit out-null config... expecially for non-ferrous items... also your phase shift will somehow balance ground phase shift in medium soils... that way you can use a back GEB setting and maybe detect e.g. silver coin at some depth more.

If you use thin ferrous foil or similar I think you'll need a far GEB setting cause of the added phase shift due to ferromagnetic materials.

Best regards,
Max

[Max]

Hi Nelson,
about Gold Bug... if I remember well it's a 19KHz machine... but you have Gold Bug II so frequency must be much great ... 71KHz I read on a pair of websites.

The extremely hi-sens to thin objects is related to the higher frequency: you get more skin effects due to that frequency and so it can find even the smallest nuggets.

Drawback is that if there is a small piece of foil you'll get a very large signal from it also at medium depth.

That kind of detectors are extremely good for gold nuggets... and I saw also that weight is about 1.3Kg, that's really good and comfortable for long run.

If you mount a 12v 1.2Ah on the box you'll increase weight of 400-450gr thus giving you 1.7-1.75Kg that's a bit heavy... so I suggest you mount regulator in the battery case inside the control box... and keep the battery hip-mounted and connected with an extensible wire... like in table phones...by a connector to the control box. That way you'll save weight from arm and shoulder and get a relative freedom of movements too.

Kind regards,
Max

[ivconic]

Hi Ivconic,
my last reading on potted coil is about 5.5mVpp that is a bit more than I have when nulled first time. I think that little forces developed due to the epoxy reactions and hardening give me that deviation respect unpotted coil.

I read that with dummy load (1Kohm+15nF) and scope.

One thing to consider is that heat generation due to epoxy... the peak of temperature easy melt or make less heavy fixed the temporary fixings of TX and RX wounds on the housing... BTW my actual housing for this DD255x137 is not the best ...made of PVC plastic that you know is really sensitive to heat and can deformate due to its action.

Anyway, my very slow epoxy (the one for surfboards) revealed a maximum peak of 68 °C (70° C on specs) I've measured before sealing coil... so heat didn't damaged too much my coil null.

Coil sealed have now same performance as it unsealed... and I'm happy of that. Just I have to wait too much for epoxy end-reactions if have to make others. I've also made another DD22 same way.

About multimeters... and nulling, when you null without capacitor I guess you don't get a perfect sinus on RX leads but a disturbed signal (due maybe to e.g. 50Hz intermodulation and similar)...

If signal is not perfectly a sinus you'll get 0.000V on a digital multimeter very easy... cause they offer good readings only with sinus shaped signals... that's so cause of their internal ADC and circuit configuration... and also at higher frequencies you get still good readings if you have a perfect sinus signal but not on an arbitrary shaped one.

So I think that when you read 0.000v there's actually some magnitude but that your multimeter can't read properly , giving you zero on display.

Adding al foil pieces is like correcting overshots in PI coils with brass washer or similar... actually I think you'll underbalance coil that way... but you know that sometimes you'll gain better sens with a bit out-null config... expecially for non-ferrous items... also your phase shift will somehow balance ground phase shift in medium soils... that way you can use a back GEB setting and maybe detect e.g. silver coin at some depth more.

If you use thin ferrous foil or similar I think you'll need a far GEB setting cause of the added phase shift due to ferromagnetic materials.

Best regards,
Max

Dont you think 5.5mV is a way to high?

I am using epoxy also. Yes you are right, it is very slow in drying...Problrm is not in that, problem is in low quality of coil housing. Cheap, recycable plastic has relative movements in time...I noticed that a while ago. That's why insisted on fiberglass housings lately. When dry, no relative movements at all.
Other....
Yes digital multimeters cant measure all signals accuratelly...Capacitor is needed there....but resistor is "sucking" to much of signal to be measured correctly...
Ooops phone is ringing....bye!

[ivconic]

"...If signal is not perfectly a sinus you'll get 0.000V on a digital multimeter very easy... cause they offer good readings only with sinus shaped signals... that's so cause of their internal ADC and circuit configuration... and also at higher frequencies you get still good readings if you have a perfect sinus signal but not on an arbitrary shaped one.

So I think that when you read 0.000v there's actually some magnitude but that your multimeter can't read properly , giving you zero on display.

Adding al foil pieces is like correcting overshots in PI coils with brass washer or similar... actually I think you'll underbalance coil that way... but you know that sometimes you'll gain better sens with a bit out-null config... expecially for non-ferrous items... also your phase shift will somehow balance ground phase shift in medium soils... that way you can use a back GEB setting and maybe detect e.g. silver coin at some depth more.

If you use thin ferrous foil or similar I think you'll need a far GEB setting cause of the added phase shift due to ferromagnetic materials...."




You understood it very well! Couldnt expect less from you. Bravo!
My initial idea was to approach to this on quite unusuall way. I decided to compromise; even to lose iron in favorite to coloured metals..but try to achieve as best as possible response on such items - coloured.
Phase is shifted more than on conventional setups, yes it is true. But response is now better by 10-20%...need to be elaborated further.
Only one thing left more.Fact that some soils consist minerals with same phase shift as "coloured" metals..Havent tested yet on such soils. I guess there will be some problems than!? I'll see.
"...medium soils..." Yes you spelled it right! This kind of setup will perform PERFECT on medium soils. It should be real killer! Yet left to be checked on other type of soils...Who knows, maybe it will turn unusable in those cases?
It is raining these days,damn! I have to wait few days to check it good...
Regards!

[Max]

Dont you think 5.5mV is a way to high?

I am using epoxy also. Yes you are right, it is very slow in drying...Problrm is not in that, problem is in low quality of coil housing. Cheap, recycable plastic has relative movements in time...I noticed that a while ago. That's why insisted on fiberglass housings lately. When dry, no relative movements at all.
Other....
Yes digital multimeters cant measure all signals accuratelly...Capacitor is needed there....but resistor is "sucking" to much of signal to be measured correctly...
Ooops phone is ringing....bye!

Hi Ivconic,
yes 5.5mVpp seems high to me. I get less than 1mVpp on other coils with a bit of patience and slow movements... but I got at first 4.5mVpp then I get now about 5.5mVpp for the DD255x137mm sealed in epoxy.

The good thing is that coil performs very good on depth and detector is now very quiet (so using original LM308N from National... not the bogus ones I posted that are for sure counterfeit parts maybe uA748 relabeled).

I don't know why I get 4.5mVpp at minimum (nulling)... but think that depends on the way overlap on coils is made. Big coil halves mean more critical overlap zones so probably there is the problem on getting less voltage.

I use epoxy and when dry I have no relative movements... but problems could arise during drying of it... the temperature increase could lose temporary fixings and so small out of null are possible... also PVC deformate with heat... that way I think I got another 1mVpp or more respect to unsealed nulled coil.

Anyway... it works fine now, no movements at all... epoxy is like solid rock inside , all around and over the wounds, and so external plastic have a very small impact on performances.

I'd like to use fiberglass housings and at least ABS plastic ones... but so far I cannot order suitable housings from US cause of lacks in communication by the dealer ! So I had to find "something" and then found just PVC stuff of that dimensions.

My original Tesoro's 9x8'' is made of ABS plastic filled with dark epoxy from the bottom... then it has a scuff cover (ABS too I think) to protect the bottom from stones etc
ABS will be good ... also better would be fiberglass or plastic with reinforced carbon sheets... but my problem is where to find them.

Best regards,
Max

[erolunall]

deep tests results

Hello all

www.staffsmetaldetectors.co.uk/depth_test.htm


Regards
Erol Ünal

[Geo]

Hello all

www.staffsmetaldetectors.co.uk/depth_test.htm


Regards
Erol Ünal

Don't believe this test' 7'' for clasicI........ 8'' for XLT, GTI 2500 and 1236???? and 9" for 1266 and X2 and X5 and ........
14'' for Explorer SE (maybe the best detector) and only the half???? for the XLT and GTI2500 (for me are similar with Explorer SE)
I believe that the writer has a sympathy to Minelab

[Geo]

To Ivconic and Max.
I believe that the best way to Null the coils is a oscilloscope . The dummy load must be a resistor and a capacitor parallel with the coil and a resistor in series with coil so the capacitance of the scope probe to don't influence the total capacitance. This is the way that i null my coils
Regards
Btw.. Ivica from who city are you??? Maybe the next month my son to come to Servia for a "Tae Kvodo " fight, i dont know yet the city.....