TESORO GOLDEN SABRE

[simonbaker]

Good fix.

LED takes some battery power -- do you really want it?

Cheers,

-SB

[metaldetector107]

TGSL ground effects

dear
Ivconic Max quazi and all
please i need your help
my problem is my device works perfect it detect a 1.5cm silver coin about
20cm with full discrimination also full reject of nail and other iron stuff
but it detect something like disoldering and something similar no problem..
my main problem is
it detects my hands from few cm also it detects ferrit from AM radio antenna from same distance i have adjested GB resistor but i canot get
lower than this distance also when moving the machin it sound like crack
i tried many ways like reduce sens ,,i tried for RX voltage from 0 to 30 mv
same thing so please help
thanks in advance

[Max]

dear
Ivconic Max quazi and all
please i need your help
my problem is my device works perfect it detect a 1.5cm silver coin about
20cm with full discrimination also full reject of nail and other iron stuff
but it detect something like disoldering and something similar no problem..
my main problem is
it detects my hands from few cm also it detects ferrit from AM radio antenna from same distance i have adjested GB resistor but i canot get
lower than this distance also when moving the machin it sound like crack
i tried many ways like reduce sens ,,i tried for RX voltage from 0 to 30 mv
same thing so please help
thanks in advance

Hi,
the hands detection is a capacitive problem: you need to shield tx and rx coils, and make so proper shield with gap like described early in this thread.

The ferrite, instead, is different: what are dimensions of ferrite you use ?

With small pieces and also toroids you can totally filter out it if machine is ground balanced ok. Really you don't even null totally ferrite out, cause small detection and few cms is good... you hear like cracks when passing at few distance (1-2cm is good, less is even better sometimes), but remember real soil is a little different from ferrite so even if md sounds with crack at few cms with ferrite it will not sound on normal soil; you can use TGS/TGSL on most soils but remember is general purpose md... so some soils will be hard and give false signals, that's why other models like e.g. bandidoII have manual geb pot... for fine adj on the field.

Now, if you detect ferrite from far (say 10-15cm) it's not good: you're not ground balanced if so, so when on soil it will give alot of false signals.

The problem could be either at coil (e.g. out from expected phase angle between tx and rx signals) or at gb trimpot setting.

If you cannot gb using trimpot to minimize ferrite like described above you're 99% with a wrong phase angle at coil. But you need scope to fix that and match expected angle (around 200° for tesoro umax coils like tgs uses).

You can fix with scope (the right way) or, if you have no scope, modify your coil if unglued by trial-and-error... till you can balance, or just make new one and cross fingers! Unfortunately this is a critical factor in good coil making cause TGS/TGSL require you match that angle for good operations.

Try to use small ferrite, 5-6cm are good for rods, small toroids are good too (2-4cm diameter). You can also make a dummy thing with epoxy and powder of iron mixed to form a coin shaped thing... 3-4cm diameter for similar purposes.

Remember: when right done you can get crack on ferrite at very few distance BUT full e.g. silver detection with loud beep in disc mode! If not you're far from good balance of your md.

Kind regards,
Max

[metaldetector107]

tgsl

Dear Max
i am happy to see u again i was waiting for you,,,
actually it does reject nail ,pliser and other iron totaly. i dont use disc switch it is always on disc mode... the ferrite is the black thingy from radio antenna it is about 7cm long and 1cm diameter when adjusting GB i
reject it till 2-3cm so i thing is good my problem today i took it to test it on soil
it gave me more fale signal when lowerd to the ground and even when movig the machine, about shielding i have shelded both with the alaminium
foil i took some out from coax cable forTV
another thing max
the TX freq is 14.7 and both coil 6mh tx 6.5mh rx
but the frequncy from pin 1 of 4024 is around 14.5 which should be same as collector of 2n2907 as you metioned already
so what do you think of these problem

thanks very much

[Max]

Dear Max
i am happy to see u again i was waiting for you,,,
actually it does reject nail ,pliser and other iron totaly. i dont use disc switch it is always on disc mode... the ferrite is the black thingy from radio antenna it is about 7cm long and 1cm diameter when adjusting GB i
reject it till 2-3cm so i thing is good my problem today i took it to test it on soil
it gave me more fale signal when lowerd to the ground and even when movig the machine, about shielding i have shelded both with the alaminium
foil i took some out from coax cable forTV
another thing max
the TX freq is 14.7 and both coil 6mh tx 6.5mh rx
but the frequncy from pin 1 of 4024 is around 14.5 which should be same as collector of 2n2907 as you metioned already
so what do you think of these problem

thanks very much

Hi,
the problem is probably related to shield only. The fact you can reject to 2-3cm a 7cm long ferrite rod (yes,it's that thing you find in am portable radios) x 1cm diameter (I think) means you have a good setting at pot and good phase at coil too.

So, if problem is with e.g. hands or soil when you lower the coil and move around it's almost sure a shield related issue.

Have you tested on green, possibly wet or humid grass ? It will go crazy if shield isn't the right way cause of static charges and capacitive effects between coils and soil or grass.

Now, the shield must be made of e.g. aluminium foil... the kind used in tv cables (coaxial I think you mean, for vhf/uhf terrestrial tv signals) could sometimes be used but only if very thin one.

Some, most of tv coaxial have heavy aluminium shield so that will somehow reduce your md performances (too heavy shield is not good cause will create too short conductive path near coils... means too eddy currents inside coil housing).

But the problem of shield you have is related to connections of it I think: you must use two separate shields , one for tx coil, one for rx coil and two wires that then bounds just at cable or pcb. Do not e.g. make rx shield touch tx shield etc (create a short turn there) and always leave the gap in both shields to avoid short turn effects.

Then you must check connections of shields to gnd of circuit, cause that's the purpose: make an electrical connection to gnd there to enstablish a fixed potential level otherwise your coils will see the influence of external charges.

The shields will also provide masking of noises (rf noise, some electrical noise around etc) but this is another issue.

Then check that connections, something is probably wrong there...fix it and it will be fine.

If you notice, instead that connections are ok, hands will give no false signals your soil is probably heavy mineralized and you're reading falses from magnetic crystals in the matrix and such can be worse than the ferrite rod used in tests.

Kind regards,
Max

[metaldetector107]

tgsl

Dear Max thanks soso much
actually i am using pulse induction MD cable which has to seperate ground ...
about green field i couldnot test it cause when i move the machine it sounds i went outside to make sure i am away from elelcrical sourses
so it was same
so my only problem now is the machine sound whenever i move it and
wherever i am .
one more thing before appling epoxy i measured the shiled ohms on of them was around 4ohms do you think is it the problem?

thanks alot

[Max]

Dear Max thanks soso much
actually i am using pulse induction MD cable which has to seperate ground ...
about green field i couldnot test it cause when i move the machine it sounds i went outside to make sure i am away from elelcrical sourses
so it was same
so my only problem now is the machine sound whenever i move it and
wherever i am .
one more thing before appling epoxy i measured the shiled ohms on of them was around 4ohms do you think is it the problem?

thanks alot

Hi,
some suggestions on mechanical aspects...
remember the coils are very sensitive to relative movements, so you must fix very well them : if used epoxy I think you fixed them ok.

Then about the pole/rod you use for coil... must be rigid, very rigid thing: choose something very strong (wood is also ok if weight is not a concern).

If metallic, like alluminium or iron or steel tube, be very careful cause ANY vibration of rod/pole relative to coils will create a false signal.

Then I suggest, if use metallic pole, don't make it arrive to the coil proximity: I mean cut e.g. 20-25cm of last part of it near coil, then make a patch with a short wood rod or plastic tube... that will be much more relaxing cause when you'll sweep coil will be difficault having a false signal from pole torsion if last part is made of wood or plastic.

The screw and wingnut you'll use at coil pivot you'll better choose in plastic made: nylon screws/plates/nuts are expecially nice there at pivot cause even if will move or vibrate (e.g. we you hit a rock) they will not give false signal to the head.

Also, the box for electronics you'll better made of plastic; if made of metallic material you must keep at good distance from coil , this is essential even if pole/rod is very rigid.

The cable of coils must be fixed to pole, lower part expecially cause movements could be detected as false signal too.

All rigid, all fixed, all silent when you move. That's the way.

These are just advices, then you could find good solutions for yourself with materials you have on hand or that could buy at your place.

The shield resistance is not a big issue: few ohms is ok. The shield, of course, must be rigid so in epoxy like with coils... no movements allowed between shields and coils or will get false signal.

Kind regards,
Max

[metaldetector107]

TGSL

dear max
the pole is plastic pipe 80cm long and the rod
or the thingy that i fixed the loop with pipe also os plastic
i took them from an old PI metal detector called P-158
only six nuts are metal which fixed the rod to the loop house
the electronic circuit house is metal box


so should i shelid the foil befor appling any tape on coil and is it should be very tight with no gaps??

thanks

[Max]

dear max
the pole is plastic pipe 80cm long and the rod
or the thingy that i fixed the loop with pipe also os plastic
i took them from an old PI metal detector called P-158
only six nuts are metal which fixed the rod to the loop house
the electronic circuit house is metal box


so should i shelid the foil befor appling any tape on coil and is it should be very tight with no gaps??

thanks

Hi,
the shield you can also not tape... but I usually do... what's important is that the shield foil will not move relative to coil windings, so stay all very strong and fixed... the best is , always, epoxing everything when the coil is made and shielded properly... that way the epoxy will block any further movement.

The pole is plastic: OK check if strong enough... must not flex when you swing the coil...

The nuts are few so I think all ok about that.

The control box is metal so must stay at least at say 60-70cm from coil (more is better cause will influence less the coil in case of vibrations). If you cannot stay too far with it... use a plastic made box if possible. All metals are a problem in control box cause the box is big object and not too far from coil (it stays in the detection range... so must stay very fixed relative to coil or at vibrations you'll get a false signal).

That's cause tgs/tgsl is very sensitive and if can detect a coke can at such distance easy (60/70cm) can detect also the movement of metallic control box. So stay far with it and very tight fixed or use plastic.

Kind regards,
Max

[kuraja]

CC

I am trying to figure out Coplanar concetric coils for tgs. I have a very rough idea about a size and diameter. Tx is 22.5 cm, Rx (wound on the same diameter as a bucking coil ) is 11cm.
Tx has 97 winds, Rx has 140 winds and a bucking coil has 25 winds.
I want to hear your opinion about this coil. I took into account that 500uH when constrained with Al foil. For the foil I am using coax foil straight from the isolation.
The whole idea came along with an old monitor stand...

[Qiaozhi]

I am trying to figure out Coplanar concetric coils for tgs. I have a very rough idea about a size and diameter. Tx is 22.5 cm, Rx (wound on the same diameter as a bucking coil ) is 11cm.
Tx has 97 winds, Rx has 140 winds and a bucking coil has 25 winds.
I want to hear your opinion about this coil. I took into account that 500uH when constrained with Al foil. For the foil I am using coax foil straight from the isolation.
The whole idea came along with an old monitor stand...

If you've never attempted to make a concentric coil before, then all I can say to you is "Good Luck!".

I don't want to put you off from your concentric coil experience, but even if you have the inductances correct, getting the correct phasing between the TX and RX coils is going to be a headache. However, if you are successful, you will have a nice coil. Unlike a DD coil, you cannot easily adjust the relative coil positions.

By the way, on a commercial Tesoro Spider coil, the RX diameter is less than half the TX diameter. There are some Chinese copies that have the RX greater than half the TX diameter, but they are not so good in practice.

[Max]

I am trying to figure out Coplanar concetric coils for tgs. I have a very rough idea about a size and diameter. Tx is 22.5 cm, Rx (wound on the same diameter as a bucking coil ) is 11cm.
Tx has 97 winds, Rx has 140 winds and a bucking coil has 25 winds.
I want to hear your opinion about this coil. I took into account that 500uH when constrained with Al foil. For the foil I am using coax foil straight from the isolation.
The whole idea came along with an old monitor stand...

Hi,
I think I posted something about some time ago... CC for TGS I mean. The idea is right... and obviously you can make it work with lot of care and efforts... but sometimes the work it needs it's too much... too much pain to make such kind of coils, and that if you already know how to make it right (inductances, tx-rx phase, nulling, shielding, formers...) and have instruments required (the scope most of all).

So I agree with Qiaozhi... if never made one... good luck.

I think the easy way is making e.g. DD or OO coils for tesoro's cause are easy to null and phase right cause you do much by just moving the coils... in geometry fixed designs (like CC) you must made tricks for e.g. null things... like lose loop or half loop... to shield (use e.g. nickel spray or graphite mostly)... to phase it right (add some pieces of foil here and there...altering both nulling and phase)... to mechanically fix it (full epoxy will result in a big weight...so you must use strategy for that if coil is not so small) etc etc

The CC are hard to do right, the increase in depth is focused just in the central area good for pinpointing but not as good for general purpose "fast" hunting.

Kind regards,
Max

[Qiaozhi]

You could also try an omega coil. It has almost the same characteristics as a concentric, but is easier to construct.

[Unregistered]

For making a open centre coil, look at post no. 22 from Golden Sabre.
I find it is easyer than making a DD coil !

Regards.

Ap

[simonbaker]

If you've never attempted to make a concentric coil before, then all I can say to you is "Good Luck!".

I don't want to put you off from your concentric coil experience, but even if you have the inductances correct, getting the correct phasing between the TX and RX coils is going to be a headache. However, if you are successful, you will have a nice coil. Unlike a DD coil, you cannot easily adjust the relative coil positions.

By the way, on a commercial Tesoro Spider coil, the RX diameter is less than half the TX diameter. There are some Chinese copies that have the RX greater than half the TX diameter, but they are not so good in practice.

I hope you try it so we can learn how you do it.

Maybe I would try this: I think I would first make RX coil and fasten it down.

Then get a long piece of wire for the TX coil, bucking coil and another 20% extra wire and wind all the wire on special spools back and forth (not in coil) so the spooled wire has approx zero inductance. When you pull the wire off the spool, each "loop" has zero inductance and will not change inductance of spool (zero).

Pull off about 10% of wire off spool and wind on another "extra spool" which also has zero inductance. This is for adjusting the TX coil later.

From the main spool, start taking wire and winding the TX coil.

If you have a calculation for the bare TX coil inductance (without the bucking coil, should be greater than 5.8 mH because you will subtract bucking coil later), do your best to wind it, checking inductance with meter as you go (connect meter to ends of the spooled wire).

After you finish preliminary TX coil, hook up a signal generator to the spooled wire ends and an oscilloscope to the RX coil.

Now continue taking wire off the main spool and winding the bucking coil. Wind the bucking coil until the RX signal on the oscilloscope hits a minimum (nulled).

Now remove the signal generator from the spooled wire and check the total inductance of the TX and bucking coil with a meter. If the inductance is too low, you need to start adding windings to the TX coil. You do this from the "extra spool". Of course you will spoil the null of the RX coil, so you will need to add some windings to the bucking coil too (from the main spool). You'll have to go back and forth until you get the correct TX + bucking coil inductance (about 5.8 mH), and also the RX signal is nulled.

Then you can cut the wire off the spool, but leave about 2 to 3 meters on each end for final adjustments in case the spools were not zero inductance.

Whew, a lot of work!

Maybe there is a better way, that's my thought.

Cheers,

-SB