White 3900D

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That's a great idea. I will wait for your results and feedback on the work.

Where can I get the PCB layout file that was posted on this thread. Is there a link?
Another point, The virtual ground(common) is set at +1.7V.
The coil, when nulled should have the Rx lead the Tx by somewhere between 40deg. and 100deg. I saw in IDX concentric coil build by Dbowers, his final null was at 90deg. So I will have to see what is optimum for this circuit.

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Coil details I intend to use (from Whites patent) 8 inch coil housing:
Tx 85 turns (27 AWG) inner diameter 6.375 inches
Rx 275 turns (31 AWG) inner diameter 3.188 inches
Bucking coil 27 turns (31 AWG) wrapped on outside of Rx coil.

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I will make this perfect working detector for others interested in building the 3900D to achieve success.
Stay tuned.

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For those who have never made concentric coil, here is something you should know:

In the preferred case, the transmit coil , the receive coil , and the feedback coil are all circular and are positioned concentric to one another so that they are all centered on a common central axis . However, it is possible that the unit formed by the receive coil and the feedback coil may be positioned somewhat off center from the axis of the transmit coil and still give good results.

So you don't have to make Rx and feedback coils at the exact centre with respect to the Tx, you can be a little "off centre", and still get good results.
So you see concentric coil design is not too difficult if you are aware of such things.

That is just one tip, there will be others to follow as I continue along.

[sayan1345]

I'm learning from you
This circuit works only disk part does nor work ...
picture of my PCB .....


my PCB is proteus file, if you want a proteus file I can send it for you
thanks

[dbanner]

I'm learning from you
This circuit works only disk part does nor work ...
picture of my PCB .....
[ATTACH]48222[/ATTACH]

my PCB is proteus file, if you want a proteus file I can send it for you
thanks

Yes, please post the proteus file here. You must put the file in a .rar or .zip archive first, then post on the thread.

I am gathering the parts and tomorrow I will etch and drill PCB. I have only one 3140 chip, so I am going to use NE5534 chip for the front end as I see in 5000/6000D scheme. This mod may require some tweaking, but I think it should be fine.
I have finished with the Sprint layout, so will be posting it as soon as I have checked that all is well with the layout and schematic.

[sayan1345]

3900D.rar

[CODE]

[/CODE]proteus file:

[dbanner]

Sayan, VR1 was measured in actual 3900D working circuit. Its value was measured to be 3.5K. So set VR1 for 3.5K.

[dbanner]

[ATTACH=CONFIG]48223[/ATTACH]proteus file:

Thanks. But the file is empty.

[sayan1345]

3900ِِِِD

I'll send the correct file again

[sayan1345]

Both files are correct, I have downloaded now

[6666]

I'll send the correct file again

I can see two files in the .rar

[dbanner]

One end of the 3.3K resistor is floating on the layout, I suppose you soldered wire directly to it for sensitivity pot.
Overall, the layout seems correct with the schematic, I haven't found any faults.
I am fairly confident that the circuit will work correctly. Only thing is the correct coil parameters and proper tuning of the resonant frequencies.

[kt315]

look https://www.geotech1.com/forums/show...ic-again/page5

[ivconic]

In meantime: