TGSL Experiments

[simonbaker]

For some strange reason, the inductance of the coil drops lower when I take it out of the former. It is tied with dental floss (mint flavor). Tying does not increase the inductance when on the former and the former is dry wood. There's not big metal lumps nearby. I feel it's about the shape of the coil; I haven't glued or epoxied it.

Therefore, I have problems predicting how much extra turns to wind to achieve the exact inductance values as recommended everywhere for TGSL (6mH for TX, 6.5mH for RX).

If I use capacitors to tune the the frequency to be 14.5kHz for TX and 16.1kHz for RX, does it matter what are the inductance values?

I remember having seen somebody mention, that the TX oscillator gives the biggest output when the value of C1 is exactly ten times that of C2. If I maintain this relationship, what are the odds that the device would still have all changes to get to the "30cm club" (if everything else is in shape)?

Yes, I know that I should make new coils. I just have run out of wire. I'll order a truckload of it, but in the meantime I would like to hear experiences from others. I also try to get dental floss with other flavor.

All hints appreciated.

I have no proof, but my feeling is that your idea is correct: just tune the resonant frequencies by tweaking the capacitors should be fine. This assumes that your coils are approximately correct inductance (within 20%).

-SB

[ivconic]

I have no proof, but my feeling is that your idea is correct: just tune the resonant frequencies by tweaking the capacitors should be fine. This assumes that your coils are approximately correct inductance (within 20%).

-SB

I agree!

[Dennis the Mennis]

For some strange reason, the inductance of the coil drops lower when I take it out of the former. It is tied with dental floss (mint flavor). Tying does not increase the inductance when on the former and the former is dry wood. There's not big metal lumps nearby. I feel it's about the shape of the coil; I haven't glued or epoxied it.

Hi Mullihaka ,

Are your coils shielded ?
I remember having 'troubles' with my experimental set up : Glued down my test set of coils with hot glue on a piece of plywood .
If I remember well I had unshielded coils and even the slightest touch of the wood caused extreme noise and alarms ....
Changed the test set up from wood to cardboard.

Therefore, I have problems predicting how much extra turns to wind to achieve the exact inductance values as recommended everywhere for TGSL (6mH for TX, 6.5mH for RX).

If I use capacitors to tune the the frequency to be 14.5kHz for TX and 16.1kHz for RX, does it matter what are the inductance values?

I remember having seen somebody mention, that the TX oscillator gives the biggest output when the value of C1 is exactly ten times that of C2. If I maintain this relationship, what are the odds that the device would still have all changes to get to the "30cm club" (if everything else is in shape)?.

Yes, I know that I should make new coils..

Why ? perhaps not ...

I just have run out of wire. I'll order a truckload of it, but in the meantime I would like to hear experiences from others. I also try to get dental floss with other flavor.

All hints appreciated.

I would recomment strawberry

never thought about a prefixed / ready to go coil shell like Georgi H Zelev is selling ?


kind regards ,

Dennis the Mennis

[satdaveuk]

Hi you proberly all think I lost it again but I did ivonics mod on the TX circuit changing the two resistors and adding a 10k pot to get a nice waveform still using the 2n2222a and the 2n2907a and now it wont oscillate, I double checked my wiring, so easy yet not working, is there something ive overlooked noticed ivonic uses a bc547 now, but that shouldnt make any difference should it?
By the way for a matter of interest whilst using a plastic unscreened housing dont advise anyone using the the metal type oscillator transistors get lots of falsing, with plastic very stable .

So wheres my problem in this simple circuit?
Remember im running at 14khz because im using Tesro coil specs ref 5.7/6.2 mh

Thanks in advance

[ivconic]

Hi you proberly all think I lost it again but I did ivonics mod on the TX circuit changing the two resistors and adding a 10k pot to get a nice waveform still using the 2n2222a and the 2n2907a and now it wont oscillate, I double checked my wiring, so easy yet not working, is there something ive overlooked noticed ivonic uses a bc547 now, but that shouldnt make any difference should it?
By the way for a matter of interest whilst using a plastic unscreened housing dont advise anyone using the the metal type oscillator transistors get lots of falsing, with plastic very stable .

So wheres my problem in this simple circuit?
Remember im running at 14khz because im using Tesro coil specs ref 5.7/6.2 mh

Thanks in advance

Mod is valid only for Musketeer coils specs and newer Tesoro coils specs - but not for older Tesoro coils specs.
Will not oscillate with 6mH coil and given tank values.

[satdaveuk]

Well your a naughty boy then because I have a circuit with the tesro coil with the actual mod on it by you, so im not the only one who has funny five minutes

[satdaveuk]

Wonder what result I would get just by putting the preset 10k in circuit leaving the other two resistors as you had them on the TGSL final, do you recon its worth a try? or will it balls it up

[simonbaker]

We already know that the TGSL oscillator is a low power design but since I started playing with this I always wondered "how low" in comparison to other detectors.

There was a link posted elsewhere in the forum that detailed making a field strength meter so I thought that I would go ahead and make use of some of the authors ideas:
http://www.5volt.eu/archives/20

Well as it turns out, you don't really need the amplifier circuit for making induced test coil voltage measurement as the signal strength is quite large enough to be accurately measured with a scope or DVM. Assuming that my scope is not loading the signal too much the figures should be a good ball-park. I just measured the peak voltages and calculated the RMS values. Then, I made use of the equations in the article to calculate "H" field magnetic strength in "microTeslas" @ 12".

Maybe Aziz or Carl can tell me if my numbers are even close or not.. But at least I can get a relative idea between detectors. Maybe I'm way off!!!

One thing that became immediately obvious is that coil size and shape has a HUGE bearing on "H field" strength at any given distance. So, I tried to group coil sizes and types together just to compare like geometry. The bottom equation shows the relationship between coil size and field strength.
Don

Hi Don:

Would it be possible to update this chart (http://www.geotech1.com/forums/showt...las#post134262) with the TX and RX inductances?

I'm very curious about the trend to low-inductance TX and high-inductance RX coils like the Musketeer in contrast to the TGSL coils.

You would think that high-inductance RX coils would pick up more noise, so you would want a very powerful TX signal to compensate. The low-inductance TX coils potentially have higher Q (as per other thread http://www.geotech1.com/forums/showt...highlight=coil) and could possibly run at higher current, but I don't know if that is the case in practice.

So I'm puzzling over why/how high-inductance RX coils work so well and seem to be preferred.

-SB

[ivconic]

Well your a naughty boy then because I have a circuit with the tesro coil with the actual mod on it by you, so im not the only one who has funny five minutes

Wait,wait!
I don't think that we understood each other well.
Come again?
Can you post here schematic (only that part of it) of what mod you applied and with what coil, and what would you like to achieve?
Sorry, but you must understand me, i have million schematics, versions, mods on my mind, and am not really sure that i understood you correctly.
Regards!

[satdaveuk]

Adjust nice TX sinus

Wait,wait!
I don't think that we understood each other well.
Come again?
Can you post here schematic (only that part of it) of what mod you applied and with what coil, and what would you like to achieve?
Sorry, but you must understand me, i have million schematics, versions, mods on my mind, and am not really sure that i understood you correctly.
Regards!

Its the adjust nice TX sinus part of the circuit, I did the modifaction to my TGSL and the oscillator went dead, changed RI to 560ohms R2= 22k and substituted the other R with a 100k preset, What did I miss? the only difference I can see is you used BC547 instead of the 2N2222A which in my eyes shouldnt matter.
I have been using the 8" Tesro coil to try and tweek to maximum, then I will go back to my home brew and go for the extra mile
Thanks for your time Ivconic

[Qiaozhi]

Its the adjust nice TX sinus part of the circuit, I did the modifaction to my TGSL and the oscillator went dead, changed RI to 560ohms R2= 22k and substituted the other R with a 100k preset, What did I miss? the only difference I can see is you used BC547 instead of the 2N2222A which in my eyes shouldnt matter.
I have been using the 8" Tesro coil to try and tweek to maximum, then I will go back to my home brew and go for the extra mile
Thanks for your time Ivconic

Have you checked the pinout?
The BC547 is in a TO-92 package, and the 2N2222A is in a TO-18. You might have it flipped over.

[ivconic]

Before switching ON your detector; adjust 100k preset to middle position, because if that values is to low - oscillator will not start at all.Than, later you can fine readjust it, by observing TX signal on scope.

[bernte_one]

Before switching ON your detector; adjust 100k preset to middle position, because if that values is to low - oscillator will not start at all.Than, later you can fine readjust it, by observing TX signal on scope.

thats exact what i did- when you turn trimmer to high there will be no more signal
if you find that point turn a little bit more down and you got a good summing sinus can haer it when speaker or headphone connected

when nulling coil with oszi you can turn this trimmer and see that effect at display
it seems that it can effect the null voltage

i think that was what ivconic meaned when he marked this point on shematic with the advice 'set to nice sinus'

p.s. i start to dream from shematics? do i go insane?


had problems to build coil housing coil is finally mounted some centimeters to big (dd or butterfly shape) 30*36cm
shielded with rescue cover (thin mylar foil) works good

video follows as soon all parts are mounted

[satdaveuk]

I tryed all that adjusting etc, must of knackered the TR when soldering, I did it in a rush in poor lighting in home, instead of workshop with all my tools.
Anyway intended to go back to the plastic type 2n2222A 2N2907A because I dont get the chirps with them.
Anyway thanks for the feedback, will let you know how I get on with it.
Regards

[ivconic]

thats exact what i did- when you turn trimmer to high there will be no more signal
if you find that point turn a little bit more down and you got a good summing sinus can haer it when speaker or headphone connected

when nulling coil with oszi you can turn this trimmer and see that effect at display
it seems that it can effect the null voltage

i think that was what ivconic meaned when he marked this point on shematic with the advice 'set to nice sinus'

p.s. i start to dream from shematics? do i go insane?


had problems to build coil housing coil is finally mounted some centimeters to big (dd or butterfly shape) 30*36cm
shielded with rescue cover (thin mylar foil) works good

video follows as soon all parts are mounted

Exactly!