TGSL Tuning & troubleshooting

[metaldetector107]

TGSL

Dear Simon


c6 0v
c12 650mv
c15 116mv

rx 6.30 26ohm
tx 5.85

thanks

[simonbaker]

Dear Simon

my scope not ready sorry, but Fr at 2n2907 collector is 14.7-8
at pin 1 of 4024 is 14.6-7 at pin2,6,7 of lf353 is 14.6..
the detection depth so poor also very very unstable despited tested shielded coil
Rx v 0.2 to 4 mv.

any help warmly recieved

What is inductance of RX coil? And resistance?

Can you measure the Rx capacitor C6?

Please measure DC voltages at C15 and C12 (relative to ground).

Regards,

-SB

[metaldetector107]

TGSL

Dear Simon

my scope not ready sorry, but Fr at 2n2907 collector is 14.7-8
at pin 1 of 4024 is 14.6-7 at pin2,6,7 of lf353 is 14.6..
the detection depth so poor also very very unstable despited tested shielded coil
Rx v 0.2 to 4 mv.

any help warmly recieved

[simonbaker]

Do you have an oscilloscope?
yes i have

Then we have no problems.

We just need to see waveforms like first few posts at the beginning of this thread.

Also coil parameters (TX, RX inductance, resistance, size). And what is your coil shield like?

Regards,

-SB

[metaldetector107]

TGSL

Do you have an oscilloscope?
yes i have

[simonbaker]

Hi
sorry the frequency is 15.1khz my meter battery was out so gave the
wrong value, ok the problem is i cannot make it quite it cracks
and detectiond range so poor.

kind regards

I harp on this a lot, but it is very important to test far away from EMI noise. I know, because in my "workshop", I cannot get more than 15 - 20 cm depth, even with dfbowers excellent MD, due to some EMI noise from somewhere.

Do you have an oscilloscope?

-SB

[metaldetector107]

TGSL-EDU

Hi
sorry the frequency is 15.1khz my meter battery was out so gave the
wrong value, ok the problem is i cannot make it quite it cracks
and detectiond range so poor.

kind regards

[dfbowers]

Hi metaldetector107:

Many times it is the frequency counter measuring double the frequency because of some problem.

Can you check with scope?

dfbowers mentioned a method to listen to the speaker tone when detecting a target and compare it with musical instrument to match the tone, and you can figure out your TX frequency.

Photos of your circuit top and back might help.

What test equipment do you have?

-SB

One thing I do is tie the anode end of the diodes to +12v with a 10k resistor. I usually hook into to my "power on" switch for +12v. That way, you get a constant tone in the speaker while adjusting turns on a coil. I turn the volume way down on my head phones. It should not hurt anything to let it run like that for extended periods.

[simonbaker]

i have build tgsl-edu board, only i hear cracks and the frequncy around
27xx khz which should be 14xx first time i did put lf353 wrongly .

please i need your help

best greets

Hi metaldetector107:

Many times it is the frequency counter measuring double the frequency because of some problem.

Can you check with scope?

dfbowers mentioned a method to listen to the speaker tone when detecting a target and compare it with musical instrument to match the tone, and you can figure out your TX frequency.

Photos of your circuit top and back might help.

What test equipment do you have?

-SB

[Jerry]

First thing you need to do is isolate what the problem is on the frequency. If the coil is the proper inductance then it has to be in the oscillator circuit. At least it is oscillating even if it is way too high so it should not be hard to track down. Much better than a dead board

Jerry

[metaldetector107]

TGSL

i have build tgsl-edu board, only i hear cracks and the frequncy around
27xx khz which should be 14xx first time i did put lf353 wrongly .

please i need your help

best greets

[simonbaker]

Thanks Qiaohzi

I think I've moved the correct posts. However, the move process only allows me to select one page at a time, and the posts get renumbered after each move. If any of them are wrong, please let me know. In general, please try to make your posts in the correct thread, as moving multiple posts can be somewhat tricky. I have already refused some previous requests due to the sheer number of posts that had to be moved.

Thanks Qiaozhi for moving the discussion of simple high-voltage coil driven by sine or square wave to other thread.

Location is now here for anyone following:

http://www.geotech1.com/forums/showthread.php?t=14655&page=15

-SB

[fmnotes]

I will prepare photographs of instrument tgsl 3 and coil and selfinduction resistance coil,
and I will go up him in the internet in order to him we examine.
I thank

[simonbaker]

Hello.
I request a question.
I have made tgsl 3.0 version.
detects 1 Euro in the 16 cm
it is well?
if exists problem,
say me what I correct.
I thank.

It depends where you are testing. EMI noise from electrical lines, etc. in your home can limit detection to 16 cm.

But if you are far away from electrical noise, you should expect around 25 to 33 cm air test according to people who are good at building the TGSL. I'm sure you have read the results from Ivconic, Max, dfbowers, etc.

So... tell us more details, show photos. Give specs of your coil (size, inductance, resistance, TX frequency, shielding, cable wiring, etc.).

-SB

[fmnotes]

Hello.
I request a question.
I have made tgsl 3.0 version.
detects 1 Euro in the 16 cm
it is well?
if exists problem,
say me what I correct.
I thank.