new tgsl sensitivity problem

[windaube]

Yes, RX is resonant at 16.12kHz but you will never see this since it is the TX frequency the RX coil picks up.
So you see 14.5kHz on RX circuit. 20 degrees of 14.5kHz = (1/14500) *(20/360) = 4us

indeed you are right

Carefully watch the phase difference between TX and TX when adjusting coil Null.
The phase shifts as the coils go through the null.
What you want is the RX signal lagging the TX by about 20 degrees when the RX signal is near minimum (null).

I noticed that if the coils are undercoupled there is phase delay and if the coils are overcoupled there is a phase advance

This is a VERY sensitive adjustment, a faction of a mm movement makes a difference.
I never got this quite right on my first DD coil. On the second one I built I did put in an adjustment screw like in the Vedio I posted a link to.
Even then, after the poured epoxy set, the slight shrinking pulled the coils out of Null and changed the phase shift.
I ground out the epoxy with a thin grinder wheel and readjusted null & phase then re-epoxied.

I also install an adjustment screw, it's really perfect!

I finished the coils with the graphite, I installed the coils in the shell
I now have around 1euro at 30CM, YESSSSSSSSSSSSSS

BUT I'm stupid...
the coils are not covered with glue, I just rolled up some tap.....
the coil is not stable! just placing your finger on the disc causes beeps beeps.....
I'm going to start making a coil again, but this time with glue to stiffen the coils......

[waltr]

Ok. 1 euro at 30cm is very good.

Maybe recheck the cable and coil shield connections.

Sensitive, YES it is.

I used clear polyurethane on the wire when winding the coils (Dbowers idea). Then soaked in some more polyurethane and allowed to dry over night. The coils where then solid.
These then got a layer of electrical tape- graphite paint with very thin drain wire- another layer of electrical tape.
Last was potting into the shell with electronic grade epoxy, done in stages-1st to secure most of the coils allowing phase adjustment, later more.

[windaube]

Maybe recheck the cable and coil shield connections.

for the wiring I use the attached picture

I used clear polyurethane on the wire when winding the coils (Dbowers idea). Then soaked in some more polyurethane and allowed to dry over night. The coils where then solid.

I don't understand, the polyuretane is liquid? I thought I would use some "super glue" (super glue 3 )

These then got a layer of electrical tape- graphite paint with very thin drain wire- another layer of electrical tape

I did like you, electric tape> graphite> earth wire> graphite> electric tape

Last was potting into the shell with electronic grade epoxy, done in stages-1st to secure most of the coils allowing phase adjustment, later more.

yes, putting the epoxy in 2 steps seems to be the best
but I can't find the balls that he mixed with the expoxy

[waltr]

Yes, polyurethane is liquid. As I wind the wire onto the form I hold a brush that was dipped in the polyurethane against the wire wetting it. The brush gets re-dipped every few turns.
This way each strand of wire is coated with polyurethane and then when it dries the wires stick together.

polyurethane is slightly flexible so allows finial shaping the the coil. CA glue is Brittle and can damage to wire's insulation if you try re-shaping the coil.

The balls are called 'micro-balloons'.
There are available from places that sell stuff to build airplanes (both models and full size) as well as boats.

A google search for "micro-balloons" should give you sources.

[windaube]

I thought the polyurethane was only in the form of plastic sheet, after research it is just wood glue.
thank you for the information.

with your method how do you manage to have the right inductance?
the final inductance is obtained after having constrained the coils with string

here is my method :
-I roll up the copper, I make the number of turns explain in manual TGSL + 5 or 6 turns
-without glue, I force the coils with string, at this moment the coil gives the final inductance.
-I plug the coil into the tgsl, generally the frequency is too low because I have too many turns
- without removing the string, I managed to remove a turn (it's difficult but not impossible) I keep the string to be sure that the inductance will not varied.
I noticed that one turn less gives about + 0.15KHZ
-I repeat the operation to get 14.5 or 13.95 Khz

in any case, I have to keep the string to have a stable inductance, so if I put the glue at the same time, I don't understand how to measure the inductance on a coil which is not constrained


I will look for the micro balls, thank you

[waltr]

Yes, the polyurethane is a Wood finish.

I made a double sided coil Form like Dbowers (see the TGLS 101.pdf). This completely constrains the coil bundle cross section when winding and with the wires coated with polyurethane the coil comes off the form without needed string.
If inductance is too low a wind can be removed since polyurethane is soft enough to allow a wire to be pulled off.

A trick if doing this with the former is ensuring the polyurethane doesn't stick to the form. I use candle Wax on the form as the release agent. Just rub a generous amount of wax onto the form before closing it.

There is more than one way to successfully make coils. I have just described the way my best coils were made.
Your method will work.

[windaube]

your method is really good !

I tried with a double-sided template, but the coil was less "compact" I always had several wire on the side that was not stretched

when the glue is dry, when you roll up electric tape the inducatance does not move?

the problem that I meet is that the inductance is perfect and the coil well constrained with the string but after the addition of the electric tape the inductance still moves
I lose about -0.15 to -0.20khz after the electric tape.

the real difficulty of tgsl is not the electrical part but the coil ! it is extremely enriching experience


I wanted to thank you for the help you bring me, you are great!

[waltr]

the real difficulty of tgsl is not the electrical part but the coil ! it is extremely enriching experience

This is very TRUE. Building a good coil is very hard the first time or two.

I had build several PI coils so had a little experience but first TGSL coil not so good.
Second one worked but not without a few problems that required unwrapping and re-doing.

Those were 10" DD coils.
I did have success on an 8" Concentric. I did have to play with the #turns on the RX and Buck coils but finally got it working.
This coil is great in trashy or iron infested places. It does not cover much ground (about 3 inch per sweep) so going is slow but it will 'see' a coin among nails.

[windaube]

I am quite satisfied with my first coil, it just works badly because of a detail that was of great importance
the coil was not rigid enough and it was not completely horizontal

for my second coil I will move the wiring in an angle, I think the connections in the center interfere with the operation

you are really determined to cut epoxy resin, personally I would have put the coil in the trash, or I will have used it as a test coil for new pcb


I do not understand the interest of the concentric coil, in France only low-end detectors have this technology
and PI detectors are very very hard to find

after the tgsl i will embark on the tesoro lobo, I find a lot of things on the internet, I will be happy to share them here afterwards
and then I think of starting a PI detector

I love the analog detector, they have default yes but they have something that the modern detector not

I will come back soon to give you news, I am just waiting for any package in the week

[windaube]

I received a "real" inductance meter, I make the coil at 6 and 6.5mH
but when I connect the coil to the tgsl the frequency is not good (~ -0.20khz)

do i have to trust the tgsl or independence meter?

[waltr]

I received a "real" inductance meter, I make the coil at 6 and 6.5mH
but when I connect the coil to the tgsl the frequency is not good (~ -0.20khz)

do i have to trust the tgsl or independence meter?

Is the coil size and number of turns correct for the recommended TGSL coil?
Did you check the coil you already made that does work with the TGSL?

[windaube]

I have the number of turns in the manual + 4 turns for two coils.

the problem is that my new inductance meter indicates 6 and 6.5mH but on the tgsl the coil resonates at ~ 14.3khz and ~ 13.75khz so about -0.2khz
I will have to remove about 2 turns to get 14.5 and 13.95khz


if I only look at the inductance meter, my coils would be OK, but if I only look at the tgsl my coils have 2 turns too many...
I have to adjust with the tgsl or with the inductance meter?

[waltr]

Oh, I mis-read your post and thought coils oscillated at 0.2kHz not -0.2kHz.

This difference could be the tolerance of the caps in the oscillator circuit.
Could also be a slight error in the inductance meter.
The error is only 1.4%. So check the Specs on the inductance meter to see if this measurement is within the tolerance of the meter's readings. Meter accuracy may only be 5%.

The exact oscillation frequency or inductance is not as important as having the difference between the TX & RX coils.

Since you have +4 turns from the manual then most likely it is the inductance meter that is off a little bit.
I would go by the oscillation frequency when connected to the TGSL.

[Ozoz_xba]

hey

the beginning of the discussion is here, this topic is dedicated only to the construction of the tgsl
https://www.geotech1.com/forums/show...-step-building
I therefore open this new topic for problem research


i built a tgsl v3.0, but it is really not responsive
I made the coil with the tgsl101 manual, the TX coil is at 14.5 khz and the rx coil is at 13.55 when it is connected to TX
the nulling was done with pin 7 of the U101

I tried the tgsl mod with -5v on the sensi pot, but the tgsl refuses to speak when I turn the sensi fully up

to better understand here is a video of the problem
https://www.youtube.com/watch?v=iwme...ature=youtu.be

I think my problem is towards U106, when I pass a 1euro coin at 20cm I have a response on pin6 U105 and Pin6 U104 but the output of the u107 does not switch.
if I spend the 1euro coins at 5 cm, I have a "longer" reponce and the output of U107 switches

I took care to test all the points of the tgsl101 manual

Huh my dso138 have the same shape of signal (not sinozoidal) ,is the problem of dso138 ,as i checked then with another oscilloskope and the shape og signal was great, by the way you have the problem with nulling i think.you can try to null it like this ,take an multimetre on the end of the coils rx (in the board or not) and try to get 3-4millivolt on the screen of multimetre by moving 1 coil near and far ,if you get 3 mvolt then you dedector will work correct and distance for 1 euro will increased .