TGSL Tuning & troubleshooting

[golfnut]

2 questions ..

1) has anyone got a link to a youtube vid of someone using an IGSL - not bench testing -but using it in the field. Is an air test approx Double what you get in soil?


2) where do you put your scope/meter during nulling?

Thanks Jerry - didnt see that first time around.

Any feedback for these as a practical detecor - or are they just an ineresting project perhaps? Playing devils advocate

Steve

[golfnut]

Hi Simon

Which is ironic because it's actually the E field that moves the current...

This is true on the Tx side - the drive volts into coil gives rise to the current flow in the coil. The alternating current creates an alternating magnetic and voltage fields - We sheild the E portion, leave the mag H part. The H - mag portion too would dissappear if the screen was closed.

The reverse is true for the Rx.

If you didnt null, the Tx field would magnetically couple in phase, (like a transformer)this alternating magnetic field coupled int the Rx coil passes thru the Rx coil windings inducing a voltage on the rx coil output terminals - In line with what you mention simon.
Steve

[golfnut]

Gettig the Rx coil to frequency

IGSL.

The Tx cct is a colpitts oscillator an runs a frequency 14.6khz (from schematic)

The Rx coil with tuning caps on scehmatic runs at 16.28khz

For best sens should these Tx and Rx be on the same frequency


Confused

Steve

[ivconic]

IGSL.

The Tx cct is a colpitts oscillator an runs a frequency 14.6khz (from schematic)

The Rx coil with tuning caps on scehmatic runs at 16.28khz

For best sens should these Tx and Rx be on the same frequency


Confused

Steve

No. It is off resonance setup.
Relation you noticed is exactly the proper one.

[golfnut]

Cheers for that, another piece of the puzzle cleared for me.

I dont understand how it all works - I would like to.

There are lots of diodes as feedback on the op amps what is that config - A limiter or some such?

Steve

[simonbaker]

Hi Simon

Which is ironic because it's actually the E field that moves the current...

This is true on the Tx side - the drive volts into coil gives rise to the current flow in the coil. The alternating current creates an alternating magnetic and voltage fields - We sheild the E portion, leave the mag H part. The H - mag portion too would dissappear if the screen was closed.

The reverse is true for the Rx.

If you didnt null, the Tx field would magnetically couple in phase, (like a transformer)this alternating magnetic field coupled int the Rx coil passes thru the Rx coil windings inducing a voltage on the rx coil output terminals - In line with what you mention simon.
Steve

I think we're talking about two different electric fields, which is OK, my point was trivial anyway.

I think you are referring to the voltage across the TX coil and possible capacitive coupling to the RX coil, which is interesting because I hadn't really thought much about that coupling and the use of the shields for that. Most people talk about shields purpose regarding wet grass static, etc.

With a USB cable we have similar coupling possibilities I think (which der_fisherman likes to reduce with a double-shielded cable).

I will think more about such voltage coupling and the effect of the shields. My experience has been that I usually get a smaller null without shields, which made me think such voltage coupling is not an issue to begin with. But worth thinking about.

Regards,

-SB

[simonbaker]

Cheers for that, another piece of the puzzle cleared for me.

I dont understand how it all works - I would like to.

There are lots of diodes as feedback on the op amps what is that config - A limiter or some such?

Steve

I believe you are right. You can sometimes see the effect on the LM308 output I think. Earlier stages hardly take effect I think. Maybe makes faster recovery.

-SB

[golfnut]

Its all very interesting stuff - seems to get you hooked pretty quick.

I really would like to see if there are those amongst you who think the IGSL is a good tool in the field.

Approx is a 12" Air test an approx 6" soil test?

Steve

[ivconic]

Its all very interesting stuff - seems to get you hooked pretty quick.

I really would like to see if there are those amongst you who think the IGSL is a good tool in the field.

Approx is a 12" Air test an approx 6" soil test?

Steve

IGSL earned me 110e already!
List back IGSL topic and find photo of silver coin i discovered the other day (50e)...
Also, already earned me another 60e for ancient roman trader weight i also discovered the other day. I didn't shot the photo of it....
It is just good as any other descent DIY detector.
Advantage could be two tones feature which tells you more infos about the target.
Less digging....or more digging, because IGSL will not shut up in situations where iron is placed near the coin.
And there are more examples, but i named them already on IGSL topic.

[Mullihaka]

How critical is the GEB adjustment?

In other words: does the GEB adjustment need to be a 10-turn pot?

I saw dfbowers to mention in the "Volksturm" thread, that he uses 10k pot for the GEB modification he made.

How about in TGSL?

[golfnut]

IGLS modes

All getting on with IGSL kit. PCB complete - 4.7uF bipolars arrived off the bay and are in.

orderd a case and bits to complete.

One thing i did not consider from schematic is D1 D2 and the 3 pins of U2 called 'choice'


what do we do here a multiway switch? anyone got a sketch i can follow

steve

[silverdog]

All getting on with IGSL kit. PCB complete - 4.7uF bipolars arrived off the bay and are in.

orderd a case and bits to complete.

One thing i did not consider from schematic is D1 D2 and the 3 pins of U2 called 'choice'


what do we do here a multiway switch? anyone got a sketch i can follow

steve

These are your choice of tones for the 2 channels, you can use any 2 depending on your preferance for a high or low tone
I think I had D1 - pin9 and D2 - pin 5

[golfnut]

Oh, ok I had thought they were modes of operation !

So simple tone selection for acoustic preference then.

Steve

[bernte_one]

my tgsl is died

hello

at the weekend after soldering something on my new igsl i thougt ok lets go in garden with my tgsl but i gives no more tones when pushing on button no more beep

i have tested battery and coil connection and also headphones somethings coming out from audio but no detector signal like the beeping i love testing also to turn pots checked the cables inside but nothing to see

so where should i start

i know there are some testing points where i could check the current i think one of the transistors is crashed

could anyone give my a troubleshooting list or link one if he knows where to find

thx

[habitbraker]

1.Check voltages - positive and negative. If there is no negative, then most likely oscillator isnt working - check it. If Voltages is below +8 and -5 then also it could be short circuit somewhere.
Check if speaker driver - its highest power part of the circuit..

If you cant find fault with multimetter and you eyes, then youll need scope...

Good luck