Problems with my new TGSL

[dfbowers]

I've mesured inductance of my rx coil,
It's 6.36 mH. Can I hope use it with a new coil (tx or rx), or I need to rebuild all two?
Otherwise I ever have download coilcalc, but I didn't know how to use it with a D coil.

You might get away with using it for a Rx coil and making another just like it with about 5 turns less. I have never been able to get my inductances quite right. As long as they are about 1.5kHz off resonance you should still be able to get the phasing right.

Here is what happens anyway. - Supposing you tune your Tx coil for 14.5kHz (6.0 mH) and by the time you add your shields and cable it will add around 400pF to your whole equation and drop your Tx frequency to 14.3kHz


In listening to Ivconics TSGL audio on some of his video posts, I'm going to guess that his Tx coil is in the neighborhood of 5.8mH.

[Sebastos34]

Hi!
I'm going to be crazy with my tgsl!
Now, I've re-build tx and rx coils, and I've 5.84mH for Tx and 6.45 for Rx. I've well balanced coils and I can get a big sesterce at 32 cms depth in all metal mode, but I have oscillations in the speaker.
G.B. Don't work properly too...
When I put it at the Max, It's rejecting coins.
I loose 10 cms depth when I use disc. And I'm not able to reject properly a ferrous.
If somebody have an idea of the source of my problems, I would wonder!!!
Thanks

[Sebastos34]

Hi,
someone could tell me how I can do with the scope, to set my oscillator with 20° between Tx an Rx, to do better balance of my coils ?
Is there a post where it's explained?
thanks

[Qiaozhi]

Hi,
someone could tell me how I can do with the scope, to set my oscillator with 20° between Tx an Rx, to do better balance of my coils ?
Is there a post where it's explained?
thanks

Have you not already performed the correct measurement procedure to obtain the first image in post #7?
Even though your phase-shift appears to be zero.

Connect channel 1 to the TX, and trigger the scope off that channel. Then connect channel 2 to the pre-amp output. Set the detector to all-metal mode, and the GB control to middle position. For a TX frequency of 14.5kHz, the phase shift between TX and RX will be about 4us at 20 degrees. Calculated from: (1/14500) * (20/360).

[Sebastos34]

Many thanks for your help Quiaozhi!
I still not understand, how to set or to verify the -20° offset...
When I have the image of my scope, how can I mesure the frequency decal. with your calculation ?

[Qiaozhi]

Many thanks for your help Quiaozhi!
I still not understand, how to set or to verify the -20° offset...
When I have the image of my scope, how can I mesure the frequency decal. with your calculation ?

Looking at image #1, and with a TX frequency of 16kHz, it appears you have the scope's timebase set to 10us. This means each major division in the X-direction is 10us. To achieve the necessary phase-shift of 20 degrees, set the coil overlap so that the zero-crossing of the RX occurs about 4us after the TX zero-crossing. In other words, imagine image #1 with the RX signal shifted to the right by 4us.

[Sebastos34]

It's very simple Like that! It's exactly what I expected!
Many thanks!!!

[Sebastos34]

Just a last question.
If I've understand well, if I'm not in phase, I can correct it by changing C6.
How can I calculate what is the best value of C6 to correct the phase?

[Qiaozhi]

Just a last question.
If I've understand well, if I'm not in phase, I can correct it by changing C6.
How can I calculate what is the best value of C6 to correct the phase?

You should not have to change any component values. As long as the coil overlap can be adjusted to give the correct phase-shift (or close to) with the GB control at its middle position, then you should be able to achieve ground balance.

[Sebastos34]

Okay, I test that as soon as possible and I tell you what returns.
Maybe my coil balance is not good.

[Dennis the Mennis]

Looking at image #1, and with a TX frequency of 16kHz, it appears you have the scope's timebase set to 10us. This means each major division in the X-direction is 10us. To achieve the necessary phase-shift of 20 degrees, set the coil overlap so that the zero-crossing of the RX occurs about 4us after the TX zero-crossing. In other words, imagine image #1 with the RX signal shifted to the right by 4us.

Hi Sebastos ,

Perhaps this is a small help and a small example what to expect ...

http://www.geotech1.com/forums/showp...postcount=4415

http://www.youtube.com/watch?v=TVrISTKtxAw


this just a example and not what you want to achive but I hope it helps you a little,

I'm also still experimenting with my coils


kind regards ,

Dennis the Mennis

[Sebastos34]

Thank you Dennis the mennis for your answer.
That's a very good help!
Today I tryed to null my coils outdoor, just with a sesterce that I moved on the coils, and I was able to detect it with a good 35 cms depth in all metal mode, and 30-35 cms in Disc mode. And with this configuration, a screwdriver is completely rejected. I'm in the good way.
I'm going to verify that with the scope to see if I can improve that.
Thanks to everybody.
When my project Will be finish,
I'll post photos of my tgsl.

[Sebastos34]

Hi,
Now I realise that when I turn gb pot. At the max, nothing is detected. And Disc pot seems to have a very little effect.
Do you think It could be an error, or a bad component on my pcb?
Thanks

[Sebastos34]

Hello,
I've tested with another coil that a friend made for me which is 5.9mH and 6.45mH for the Rx, and I have the same problem with GB pot. and disc pot.
I've verified all components and all seems to be ok.
Somebody knows where is the problem please?
Thanks

[KRISEMA]

salut seb meme problème pour moi
faut que je trouve le temps de t appeler, mais en ce moment je part tot et rentre tard et du coup je n ose pas t appeler je viens de refaire une autre bobine, et ma foie j ai eu de meilleurs résultats sans blindage que avec je me demande si ce fameux adhésif alu n ai pas trop gros chose bizarre aussi mon pot disc discrimine une pince coupante sur la position zéro et des que je monte un peut le pot il me la prend je viens de vérifier toutes mes tentions j ai -6,27 volts la ou je devrait avoir -5v pour ce qui est du rejet de la ferrite impossible