Does anyone know anything about this old Pi detector circuit?

[GeoMax]

Hello forum members,

A long time ago, I got this old PI circuit diagram from somewhere. Unfortunately, the project documentation is incomplete. I have only this page. It looks like it's a PI detector from the 1980s/90s, photographed from an electronics magazine. Judging by the language, I think the text is in Hungarian. Does anyone recognize this project or project name and perhaps have the complete article? Or does anyone know when and in which electronics magazine the article was published?
The quality of the page is not the best.

Thanks

[algan]

Interesting scheme, how does it work, is it dynamic or static mode here?

[pechkata]

Yes - maybe a combination with this one.

[GeoMax]

Interesting scheme, how does it work, is it dynamic or static mode here?

Hi Algan
I'm trying to figure that out too. It's a slightly different approach than usually seen. That's why I need the help of the forum community to find the full article. Perhaps someone has a copy of the original article and could post it here.

[boilcoil]

Maybe this will help.



PI_metedet.rar

[GeoMax]

Maybe this will help.
[ATTACH]n447596[/ATTACH]

Perfect! This article contains almost the same circuit diagram. This will help to better understand the design.

Thanks.

[boilcoil]

Now I looked in more detail at the schematic from the post I uploaded.
There is an error (most likely from haste in drawing the diagram).
The coil, R27, and R25 should be connected to +9V, not +16V.
And R15 to +16V.

Everything else should be correct.

[pechkata]

And where do these 9 - 16 volts come from?
And this chip - it's difficult.

[pechkata]

Hello forum members,

A long time ago, I got this old PI circuit diagram from somewhere. Unfortunately, the project documentation is incomplete. I have only this page. It looks like it's a PI detector from the 1980s/90s, photographed from an electronics magazine. Judging by the language, I think the text is in Hungarian. Does anyone recognize this project or project name and perhaps have the complete article? Or does anyone know when and in which electronics magazine the article was published?
The quality of the page is not the best.

Thanks

I think this scheme is more correct.

[GeoMax]

Now I looked in more detail at the schematic from the post I uploaded.
There is an error (most likely from haste in drawing the diagram).
The coil, R27, and R25 should be connected to +9V, not +16V.
And R15 to +16V.

Everything else should be correct.

Hi,
thanks for the information.

[GeoMax]

And where do these 9 - 16 volts come from?

The 9V voltage comes from a battery. However, this is not shown here.

[GeoMax]

Now I looked in more detail at the schematic from the post I uploaded.
There is an error (most likely from haste in drawing the diagram).
The coil, R27, and R25 should be connected to +9V, not +16V.
And R15 to +16V.

Everything else should be correct.

Hello BoilCoil,

R25 in the Stuart circuit diagram corresponds to R32 in the other circuit diagram and is also connected to +16 V there. But I also think R25 (R32) should be connected to +9V and not to +16V

[algan]

R25 in the Stuart circuit diagram corresponds to R32 in the other circuit diagram and is also connected to +16 V there. But I also think R25 (R32) should be connected to +9V and not to +16V
[/QUOTE]

R25 (R32) should be connected to +16 V, this is correct, because in the circuits here the npn transistor inverts the signal, in this circuit +9V is GND. The interesting thing in this case is, this connection between the keys of the 4066 maybe you should check how this works.

[boilcoil]

R25 in the Stuart circuit diagram corresponds to R32 in the other circuit diagram and is also connected to +16 V there. But I also think R25 (R32) should be connected to +9V and not to +16V

In reality, the voltage on R25 (R32) is the voltage to turn on the MOSFET, through the integrator circuit with the time constant Cin*R25 (R32), where Cin is the input capacitance of TR4. Connecting R25 (R32) to +9V would increase the turn-on time of TR4, but would unload the circuit for supplying positive voltage to the operational amplifiers (and the associated noise generation when switching the driver transistor TR3). I personally would connect R25 (R32) to +9V, reducing its value to about 2k to 5k, to guarantee high-speed tirn on (which in this case is not relevant to the proper operation of the metal detector) .

So, looking at the +16V and +9V circuits, another error is found - the positive supply of IC4 LM318 should be from +16V, not from +9V ( in this case +9V is the analog ground of the device).

[algan]

GeoMax's circuit is correct and from plus 16 volts a 7805 stabilizer can be used, plus 9 volts to the stabilizer's ground, if necessary another 7905 stabilizer can be used for minus 5 volts where negative is needed and test how it works.