TGSL Tuning & troubleshooting

[simonbaker]

Hi Johnsmith ,

What did you use for shielding your coils ?
Are your coils shielded ?

Did you try to adjust the coils without shielding ?
In my opinion you can try to adjust the coils without shielding in this case only for test purpose.

My experience with unshielded coils was that they seem to behave as a 'perfect' coil what nulling / adjusting concerns .

So to determine if your problem is in the coils or not , you can try without shielding ...

Your detection may become more (or too) sensitive at this point ( unusable ).

It is worth the try .

Although many had great results with Al foil , I did not and was running around in circles for quite a time in order to achieve the ideal phase shift ...

But as Simon and Don said :



Here's an example of an unshielded set of coils for comparisment:

http://youtu.be/3hY4s6_cKw4

and a example of with Mylar shielded coils ( at this point I thought there was a relation between the isolation thickness between coil and shield wich is not true . ( running around in circles makes you stick
Later I removed the 'isolation' and putted the Mylar direct on the coils

http://youtu.be/N7yrp8l_fSU.

I hope this is of any help



kind regards,

Dennis the Mennis

Good suggestion to try without shields (assuming not a lot of work ) -- we may learn more from that.

Maybe Dennis the Mennis can also talk you (johnsmith77) into getting a PC PicoScope which he has used very successfully. I'd like to get one myself.

-SB

[Dennis the Mennis]

My results.

Phase diff tx J2-1 / lf353 pin 7:

a) undernulled: ~ 160 degrees, negative shift
b) nulled: - 60 degrees, negative
c) overnulled: ~ 40 degrees, positive.

C12, C15 voltages.

a) undernulled:

c12, -0,7v
c15, -0,7v

b) nulled:

C12, -0.2v
c15, +0,2v

c) overnulled:

c12, -0,7v
c15, -1,4v

Best Regards

Hi Johnsmith ,

What did you use for shielding your coils ?
Are your coils shielded ?

Did you try to adjust the coils without shielding ?
In my opinion you can try to adjust the coils without shielding in this case only for test purpose.

My experience with unshielded coils was that they seem to behave as a 'perfect' coil what nulling / adjusting concerns .

So to determine if your problem is in the coils or not , you can try without shielding ...

Your detection may become more (or too) sensitive at this point ( unusable ).

It is worth the try .

Although many had great results with Al foil , I did not and was running around in circles for quite a time in order to achieve the ideal phase shift ...

But as Simon and Don said :

Ok, here's the thing with RX null signal phase -- it can really vary a lot, depending on how you null your coils, and what kind of shield you have. And people have different theories on what is best. However, if you follow a procedure to null your coil using ferrite, and if your RX circuit has correct resonant frequency relative to the TX frequency, then you probably don't need to worry at all about what phase your null signal is.

Here's an example of an unshielded set of coils for comparisment:

http://youtu.be/3hY4s6_cKw4

and a example of with Mylar shielded coils ( at this point I thought there was a relation between the isolation thickness between coil and shield wich is not true . ( running around in circles makes you stick
Later I removed the 'isolation' and putted the Mylar direct on the coils

http://youtu.be/N7yrp8l_fSU.

I hope this is of any help



kind regards,

Dennis the Mennis

[simonbaker]

hello 2 any 1
I have a problem on my TGSL I hope to find Solution with Your advice.
I can Get coin in air 30cm and Rejection of iron . the problem when move the coin near to coil I get high sound when move coin in 20cm or 30cm Sound becomes very very weak.
What I do to get loud voice in 10cm or 20 or 30cm
Note: I dont have problem in my PCB

My previous suggestion (with bigger capacitors) was to make the beep longer, in case your problem is too short a beep with weak targets.

However, if your real problem is simply loudness, then you can try this:

Disconnect the 100k resistor R40 from U105 pin 6 (output of LM308 GB channel) and connect it to V+ voltage.

This should help give you same volume sound for all beeps (except very short ones). But it may be too loud, so you may need to use a voltage divider to get smaller voltage than V+.

P.S. I haven't tried this so you would need to experiment.

-SB

[Qiaozhi]

You attached placement.pdf. My tgsl is made by this pcb, but the sound in 30cm is the same as in 10cm. It is too strong, i plan put pot for sound adjustement. I have too strong sound, you have too weak Do you hear cracks in 30cm or just weak beeps?

By the way, how do you reached 30cm? I see earlier posts, you had only 20cm.

This is because Tesoro detectors do not have a volume control. If you plug in headphones, they must have volume controls built-in - like these ->

[johnsmith77]

hello johnsmith77
First I want to thank you for your interest.
rejection iron of any distance Whether large or small and ferrite too.
by the way I use tl071 replacement for LM308.
Sorry I'm weak in English
Greetings

You attached placement.pdf. My tgsl is made by this pcb, but the sound in 30cm is the same as in 10cm. It is too strong, i plan put pot for sound adjustement. I have too strong sound, you have too weak Do you hear cracks in 30cm or just weak beeps?

By the way, how do you reached 30cm? I see earlier posts, you had only 20cm.

[Dennis the Mennis]

hello 2 any 1
I have a problem on my TGSL I hope to find Solution with Your advice.
I can Get coin in air 30cm and Rejection of iron . the problem when move the coin near to coil I get high sound when move coin in 20cm or 30cm Sound becomes very very weak.
What I do to get loud voice in 10cm or 20 or 30cm
Note: I dont have problem in my PCB

Hi Salih ,

It is a normal when a target is very near the coil the audio is very loud ( depending of the size of the target) .
If the same target is moved away from the coil , it is normal that the audio becomes weaker ....
You can try the modifications described in the forums , they may fit you .
Did you try another speaker or earplugs ?

kind regards

Dennis the Mennis

[salih]

Some news. In am mode i hear single beeps always. In disc mode when metal is discriminated i hear double beep. It even could be used, if one beep than "dig"; if two beeps - "trash". But but there is two beeps for ferrite also

hello johnsmith77
First I want to thank you for your interest.
rejection iron of any distance Whether large or small and ferrite too.
by the way I use tl071 replacement for LM308.
Sorry I'm weak in English
Greetings

[Jerry]

Ok..... Took a while but here it is:

http://www.geotech1.com/forums/showthread.php?p=75295&highlight=tgsl+555#post75295

Jerry

[homefire]

Yep! You have a audio pitcher of were the target is the way it is.

[Jerry]

hello 2 any 1
I have a problem on my TGSL I hope to find Solution with Your advice.
I can Get coin in air 30cm and Rejection of iron . the problem when move the coin near to coil I get high sound when move coin in 20cm or 30cm Sound becomes very very weak.
What I do to get loud voice in 10cm or 20 or 30cm
Note: I dont have problem in my PCB

I dont think you have a problem with TGSL either. 30cm is a good air test. Will be interesting to see how it performs in the field.

Having the sound drop off in volume as the distance increases would be an advantage for me. Once you get used to the detector, you will be able to tell approximate depth of a coin by listening to the beep.

Ivconic did an audio modification a couple years ago using a 555 timer to drive the audio stage. This gave the same volume at any depth that the TGSL would pick something up.
As I recall, the reason he did not like it was because the sound was the same all the time. I have it printed out somewhere, I will see if I can find the posts made about it.

Sorry I cant be of more help.

Jerry

[simonbaker]

My results.

Phase diff tx J2-1 / lf353 pin 7:

a) undernulled: ~ 160 degrees, negative shift
b) nulled: - 60 degrees, negative
c) overnulled: ~ 40 degrees, positive.

C12, C15 voltages.

a) undernulled:

c12, -0,7v
c15, -0,7v

b) nulled:

C12, -0.2v
c15, +0,2v

c) overnulled:

c12, -0,7v
c15, -1,4v

Best Regards

Thanks, I'll need to think about this for a while.

-SB

[simonbaker]

hello 2 any 1
I have a problem on my TGSL I hope to find Solution with Your advice.
I can Get coin in air 30cm and Rejection of iron . the problem when move the coin near to coil I get high sound when move coin in 20cm or 30cm Sound becomes very very weak.
What I do to get loud voice in 10cm or 20 or 30cm
Note: I dont have problem in my PCB

You could try increasing the values of C17 and C14 (4.7 uF) to up to 20uF. Or change capacitor C18, C21 from .47uF to 2uF. You may not like the response though.

Another problem is noise -- any noise in your workshop can make the target beep shorter and sound fainter. Test again far away from noise.

Also look for Ivconic's experiments with audio circuit.

-SB

[salih]

help

hello 2 any 1
I have a problem on my TGSL I hope to find Solution with Your advice.
I can Get coin in air 30cm and Rejection of iron . the problem when move the coin near to coil I get high sound when move coin in 20cm or 30cm Sound becomes very very weak.
What I do to get loud voice in 10cm or 20 or 30cm
Note: I dont have problem in my PCB

[simonbaker]

Ok.... The pictures are a representation rather than from your sound card scope. If this scope is not stable enough to get a good picture of both traces you are taking a lot on faith that the 12Us shift is accurate.

This whole discussion may not matter in the long run if it is working ok.

Here is a graph that I made last year showing the relationship of the coil phase shift to the null voltage. It may help shed some light on things.

Jerry

Remember this type of graph, as I hope to return to it with an underlying model that would help make it more widely applicable.

[johnsmith77]

Some news. In am mode i hear single beeps always. In disc mode when metal is discriminated i hear double beep. It even could be used, if one beep than "dig"; if two beeps - "trash". But but there is two beeps for ferrite also