IDX-PRO+VDI

[h9361]

First remove C5 and C6 and move the same capacitors at the input to the amplifiers or behind 100k! My TX capacitor is 470 nf with 45 circles of 0.45 mm thick wire and rx 140 circles and 0.25 mm thick. And R25 replaced from 10k to 1k..

Thank you for your guidance.
See attached, is the changing true (C5 and C6)?

Please see the PCB, i think R25 is 47R. Is it true?
Now i am using 47R.


About your inductance, i measured for 30cm coil.
I think your
TX is 1.3mH, with 470 nF, Frequency is 6.4Khz (0.45mm wire)
RX is 13mH, (0.25mm wire)
Do you remember your RX capacitor?

[Orbit]

To connect the capacitors as shown in the diagram! Not going into the details of the pcb because I've never used that pcb.Just place the capacitors as I mentioned and as you moved them on the scheme you posted and let me know if there are any improvements..

[Aleks85]

Here is a normal, working diagram; it was according to this scheme that I assembled several metal detectors.
It is very important to make a normal sensor, the main thing here is the correct wire diameter - at least 0.6 mm for TX and an inductance of 0.580 mH, for PX the wire is 0.18...0.24 mm and an inductance of 36 mH, then it is important to set the frequencies of TX - 6.59 kHz and PX 4.6 kHz.
In this metal detector you need to very accurately set the TX and PX frequencies, only then will it work normally and have good sensitivity.
You also need high-quality components, now they sell a lot of bad radio components, and if you bought them for good money, this does not mean that the part is of high quality. I described how you can simply check a microcircuit, there is nothing complicated here, in the end you can be sure whether it is of high quality or not.

[h9361]

Here is a normal, working diagram; it was according to this scheme that I assembled several metal detectors.
It is very important to make a normal sensor, the main thing here is the correct wire diameter - at least 0.6 mm for TX and an inductance of 0.580 mH, for PX the wire is 0.18...0.24 mm and an inductance of 36 mH, then it is important to set the frequencies of TX - 6.59 kHz and PX 4.6 kHz.
In this metal detector you need to very accurately set the TX and PX frequencies, only then will it work normally and have good sensitivity.
You also need high-quality components, now they sell a lot of bad radio components, and if you bought them for good money, this does not mean that the part is of high quality. I described how you can simply check a microcircuit, there is nothing complicated here, in the end you can be sure whether it is of high quality or not.

Thank you.
Do you remember your Air testing distance?
Now, i am doing Mr. Orbit suggestion on my PCB.

[Smirnov-Arta]

///

Please don't take offense, but... once you take the unit out into the field, you'll see that's not the case at all. Again, even if you do manage to achieve 1–2 Amps at the coil, the gain in depth in actual soil will be negligible compared to the resulting instability of the device's overall operation. Believe me, it’s a dead end. But that’s up to you.

[Sergey_P]

for PX the wire is 0.18...0.24 mm and an inductance of 36 mH, then it is important to set the frequencies of TX - 6.59 kHz and PX 4.6 kHz.

It's best to use wire 0.24 mm thick or thicker with an additional resistor to achieve a total resistance of R(L) of ~67 ohms. 272 turns per coil with a diameter of 20 cm. In this case, the phase shift in the coil will be close to the phase shift of the surrounding ground, and the influence of the ground on the phase will be minimal.

[Aleks85]

I used 0.24 mm wire for the RX; it was hard to find anything else for free. I only made concentric sensors; for a 24 cm diameter, the air sensitivity was 30...35 cm (about five kopecks in the USSR), and a little less in the ground, but not lower than 25 cm.
The TX amplitude was 16 volts from peak to peak with the generator powered by 8 volts, this metal detector does not need more.

[pechkata]

[Aleks85]

This describes a simple test of operational amplifiers, everything is in Russian, anyone who needs it can translate it. Just look at the oscillogram and it will be clear which microcircuit is normal and which is defective.

[h9361]

To connect the capacitors as shown in the diagram! Not going into the details of the pcb because I've never used that pcb.Just place the capacitors as I mentioned and as you moved them on the scheme you posted and let me know if there are any improvements..

Dear Orbit
I changed position of two capacitors, as you told.
No change to depth.
But i changed IC brand, now my depth for the coin is near 42 cm.
I made your dc convert voltage, it works very nice.
Thank you.

[h9361]

The RX resistance matters very little. The higher TX resistance will add a small amount of phase rotation that is removed with the ground calibration. The resistances you have will work, and are not the cause of your lower sensitivity.

Hello dear carl.
Please forgive me, i have a request.
Please see IDX schematic audio part, post #4378.
Unfortunately its audio level in speaker is very low.
Is it possible to help me how to increase its audio in speaker?
I tested it with 15, 25, 150R speaker.
Thanks

[Orbit]

Dear Orbit
I changed position of two capacitors, as you told.
No change to depth.
But i changed IC brand, now my depth for the coin is near 42 cm.
I made your dc convert voltage, it works very nice.
Thank you.

Those capacitors make the signal cleaner. Reconnect the pin point and adjust the pot trimmer to barely audible and leave the setting like that. You could also replace the input number 5534 with AD711. As for the sound Karl I know he will give you good advice. My suggestion is to put an 8R speaker and relax the mpsa13 transistor by replacing it with a bst 52 or similar.

[Carl-NC]

Is it possible to help me how to increase its audio in speaker?
I tested it with 15, 25, 150R speaker.

An 8-ohm or 4-ohm speaker might be louder. However, the speaker is DC-coupled and you run the risk drawing a lot of static current. Here is a simple circuit I used in ITMD3 projects:


In your case, VTX is Vbatt, VCC is your "+" supply, and Q3 (your Q4) can remain as an MPSA13 although a non-Darlington NPN might give a little more loudness.

[h9361]

Those capacitors make the signal cleaner. Reconnect the pin point and adjust the pot trimmer to barely audible and leave the setting like that. You could also replace the input number 5534 with AD711. As for the sound Karl I know he will give you good advice. My suggestion is to put an 8R speaker and relax the mpsa13 transistor by replacing it with a bst 52 or similar.

Thanks
You right, my noise is low by the changing.
I can not understand bst 52.

[h9361]

An 8-ohm or 4-ohm speaker might be louder. However, the speaker is DC-coupled and you run the risk drawing a lot of static current. Here is a simple circuit I used in ITMD3 projects:


In your case, VTX is Vbatt, VCC is your "+" supply, and Q3 (your Q4) can remain as an MPSA13 although a non-Darlington NPN might give a little more loudness.

Very thanks dear Carl
GND is generated in IDX by u7-pine 7.
In your LM386, gnd is the pine 7 or _VB?