TGSL SMD

[Hyena]

All freq is correct, pin7 opamp 0.4v, air test only 16cm at max sens
[ATTACH]41893[/ATTACH]
Using Ne5532 as lf353 and 2N5485 for bf245
Let me try another ic and transistor

That shape is very strange, can you shot Tx?

[ripsdevala]

Did you try to use a standard DD coil with this pcb?
Im interested if it works. Because i want to build one too.

I did, 20cm DD same result

That shape is very strange, can you shot Tx?

Please check... Tx yellow, Rx green

[dbanner]

waves look good, phase looks off, coil nulling maybe could be better, tx amplitude should be in 16v range

[dbanner]

ground balance

[ripsdevala]

Tx amplitude16v? do you mean the voltage of tx? Its 0.02v
I need to learn oscilloscope more


GB is ok, pot at the middle slighty right.
Nulling, i find the lowest voltage from preamp pin7, is there another way better?

[Hyena]

Tx amplitude16v? do you mean the voltage of tx? Its 0.02v
I need to learn oscilloscope more
[ATTACH]41895[/ATTACH]

GB is ok, pot at the middle slighty right.
Nulling, i find the lowest voltage from preamp pin7, is there another way better?

I bet your problem is in coil as always Vpp on Tx is 15V and it is correct. But the phase shift is really strange. I made only 2 concentrics in the past, but always had 200° phase shift. You have something like 345-350°. Do you get double tone when target is present? Did you try swap Rx cables?

[Koala]

Tx amplitude16v? do you mean the voltage of tx? Its 0.02v
I need to learn oscilloscope more
[ATTACH]41895[/ATTACH]

GB is ok, pot at the middle slighty right.
Nulling, i find the lowest voltage from preamp pin7, is there another way better?

what voltage are you getting. Anything under 200mv should be good. If the phase is too far out it will affect depth on certain metals. Have you tried lead aluminium silver gold and so on. Are they all bad.?

[dbanner]

This is video of DD coil nulling using scope. Notice how phase shifts. https://www.youtube.com/watch?v=VZSawpu9Ako

[dbanner]

Here is even better video https://www.youtube.com/watch?v=TVrISTKtxAw

[ripsdevala]

I bet your problem is in coil as always Vpp on Tx is 15V and it is correct. But the phase shift is really strange. I made only 2 concentrics in the past, but always had 200° phase shift. You have something like 345-350°. Do you get double tone when target is present? Did you try swap Rx cables?

No double tone, swap rx make double tone.

what voltage are you getting. Anything under 200mv should be good. If the phase is too far out it will affect depth on certain metals. Have you tried lead aluminium silver gold and so on. Are they all bad.?

Yes its under 200mv but its to easy, something not right, and i dont get chater noise at all like the ussual, and you right aluminum is not detected in all metal mode...

[ripsdevala]

Progresss. ...
I csn get 25cm air deep now, BUT! can't GB!.. meeh

[dfbowers]

Progresss. ...
I csn get 25cm air deep now, BUT! can't GB!.. meeh

A little trick I use when building my coils - I have a simple DVM that can measure frequency. I adjust my windings so that Tx runs at 14.5kHz. Then... attach your Rx coil to the oscillator and adjust winding to 13.9kHz (just for tuning purposes). When you put everything back, it should be perfect every time! You should be able to set the GB pot somewhere midrange then.. AND, make sure that you can still detect thin silver in disc and AM modes. If not, your problem is not with the coil. I may try the TGSL SDM as my next project as well.
Don..

[ripsdevala]

Now all fine, GB ok, null from dmm 0.019v Detection deep only 20cm with medium brass coin.... Strange no chatter at all, its should be noisy.... Maybe a little more tune somewhere.
And the silver...let me check
Silver rings is detected

[Koala]

Still sounds a bit short. I built the Bandido. Which is very similar. From memory my smallest coin about the size of a little finger nail starts at 7" and I know I can just pick up UK pre decimal coin in the ground at 10" and around 12" in the air. That's with a 5.5" coil.


Yes when the sense is fully up and the coil isn't in motion it chips a bit. Not that I ever ran the machine on full sensitivity.

[ripsdevala]

My best is 27cm with v3, never get 30cm before, idk.
Some tune... 23cm clear beep... Need more

Tell me how to proper phase shift with scope, what probe to connect, timing base, im not sure what im doing