TGSL SMD

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

[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.?

[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?

[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?

[dbanner]

ground balance

[dbanner]

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

[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

[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?

[BKY1337]

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

[ripsdevala]

My LCR is also big liar when it comes to inductance. I ordered DMM, which can measure inductance well and I was surprised by LCR error size It was in some cases up to 20%.

OK, and measure residual voltage after your correction!

All freq is correct, pin7 opamp 0.4v, air test only 16cm at max sens

Using Ne5532 as lf353 and 2N5485 for bf245
Let me try another ic and transistor

[BKY1337]

Has somebody a partslist for the v1 layout?
Because im ordering parts.

[Hyena]

My LCR is also big liar when it comes to inductance. I ordered DMM, which can measure inductance well and I was surprised by LCR error size It was in some cases up to 20%.

OK, and measure residual voltage after your correction!

[ripsdevala]

With 3mH inductor 20.51khz, i think the board is ok.
My lcr is crazy, thanks for the support, i need to reduce my coil winding to the required freq

[ripsdevala]

Ok, let me check, i only have this freq dmm and hantek scope

[Hyena]

I'm not sure with ny lcr...
[ATTACH]41886[/ATTACH]
[ATTACH]41887[/ATTACH]

What frequency should i get when i attach 3mH inductor to Tx J1, just for test.

Can you measure residual voltage + phase shift after first op amp Rx?

For 220n 22n and 3mH it should be 20,539 kHz