VLF MD (by Sascho - Varna)

[xycy]

Yes the scheme is that. Is somebody made it. Is it stable enough, is the sensitivity as its written on it 30 cm/5 st. in the ground, can it compensate the ground effect. Also there is some details which haven't values: on the input '+' of the upper 741 op-amp. How the sound come up: is the last IC 555...
I'd like to compare it with the Sasho's circuit which is with 2 CD4007 and 2x19cm. coils mentioned in other threads.
If someone can help I would be very thankfull.

[scs]

Sascho scheme works very well in 8 khz.Transmitter and resiver coils capacitor must be 68nf.

[maikl]

Yes the scheme is that. Is somebody made it. Is it stable enough, is the sensitivity as its written on it 30 cm/5 st. in the ground, can it compensate the ground effect. Also there is some details which haven't values: on the input '+' of the upper 741 op-amp. How the sound come up: is the last IC 555...
I'd like to compare it with the Sasho's circuit which is with 2 CD4007 and 2x19cm. coils mentioned in other threads.
If someone can help I would be very thankfull.

Grozdanka is a good detector, Sascho's is a little better and and have more details about the construction. But pay attention to Pompey comment #143.

[xycy]

OK, 50cm/1 euro is fine. I think its on ear. As far as I understood he uses a bigger coil 2x21cm or so. What about the 2x19cm coils? How much is the depth with them. Can I get 20mm coin in 30cm in the ground. And how it behaves on the beach? Can it work in wet with salted water sand? Is someone made such tests?

[scs]

BG detector-corrected schematic.This is not old legendary GROZDANKA schematic from ing.Grozdio Grozdev.

[scs]

[xycy]

I see. So you have made it right. Then tell me please the result of it: depth, can it be used on beach. Also the values of C and R on the '+' input of 741. I think I can use LM324 instead of 2x741 and 1/4 for sound generator instead 555. Instead tl081 I shall use LF356. What you think about.
You said that Sasho's scheme is a bit better: in what its better - in depth, in stability....
Tnx

[maikl]

Hi xycy.
Sorry I made a mistake with Pompey post, is not # 143 I thought of #142, where he gives advice to do another project of Sasha - "S1".
Sasho's scheme (with 2 CD4007) is a bit better in stability, I think it can not be used for the beach with salt water. "S1" that could be used on the beach (unfortunately, "S1" has a bad audio discrimination)...
And you xycy if you want to build a certain "Bulgarian Legend", here's some schemes:

[maikl]

Here's more:

[maikl]

And more:

[xycy]

Tnx Maikl. Can you tell me the values of the resistors to pin 1 and 7 of LM393 on Sasho1 circuit please. I suppose that I can use tl084 instead of 2xtl062.

[maikl]

Resistors to pin 1 and 7 of LM393 on Sasho1 circuit is: R26=22K and R25=22K. Try the TL084. Here's a link to this forum where you have more details about the construction (pay attention to "S1" and not "S") http://www.geotech1.com/forums/showt...metal-detector
It seems interesting "Slow motion detector" (Sasho's latest project VLF), i have not built it, i might in the winter http://www.thunting.com/smf/vlf_desi...-t28279.0.html
But I see you've decided to build a Surf PI...

[xycy]

I built SM and im working with it. But I need much depth. I'd like to build something with better depth results. Also I wander which circiut to choose: Grozdanka or S1 with 2x4007 or even Tarsos. Although for the last one there are not too good reports. For big circuits PCB is a problem.
Tnx

[maikl]

What results did you get with the SM ("Slow motion detector"), for example, how the detection of a euro coin?
Tarsos do not build a, poor performance on the field.
Because you want the search to depth and saltwater beach, it may be better to build a Baracuda PI or Surf PI.

[xycy]

SM I have put for Surf Master. It works in the wit sand but I need ~30cm depth in the ground. Also I don't like very difficult circuit just its difficult to make the PCB. Did you build S1 or Slow M. or Baracuda. Tell me please their performance. Which one would you recommend.