Signal synthesis for simple PI detector

[ivconic]

Only the truè insiders can spot and correct the intentional errors you plant in your schematics. They're made for the elite, the peasants is left with a dead board and scratching their heads. Devious!

If you think I made a deliberate mistake with the mosfet polarity symbol... you couldn't be further from the truth.
This is not the first time. I think Moodz already pointed it out once on one of my earlier schematics.
It's the ExpressSch software (from the ExpressPCB package) that I've been using for years to draw schematics.
I stubbornly did not want to switch to one of the newer versions, for years I used the old version, one of the first.
And I got into the habit of using some components incorrectly.
In the previous post I was joking with Moodz, of course it is a serious mistake and who is off topic; he may have a problem because of that.
But Barracuda is too well known and mentioned topic, there are many topics on the forum dedicated to that project, even the birds on the branch
already know that P-channel mosfet is used in TX.
The one who did not already know this and is not able to notice such a mistake by himself (there is a mosfet mark next to the symbol);
he is not immediately ready to work with this kind of detector. Although it seems simple, it is far from easy to make.
But I certainly accept the blame.
Later I started using a new version of the software in which I have better done component symbols.
And in the meantime, I myself made a lot of custom symbols for use in that software.
That schematic still dates from before, it was not made yesterday. The forum is full of them.
It is recommended to do the original Barracuda first and the best pcb for that is the one offered by ApBerg.
No, really I'm not that "cunning" and I don't set "traps" in my schematics.
All my mistakes are unintentional and accidental. And the reason for that is my laziness and inertia.
...
The schematic I presented here is purely "academic". Only one step towards the final version.
What will you get if you build that detector? Nothing special.
Barracuda that works a little "cleaner" and more precisely. And nothing more than that.
It is not a noteworthy success.
That's why I rather recommend building the original Barracuda.
And this is just my attempt at porting some of the hardware to the mcu.
A little experiment and nothing more.
The division into "elite" and "peasants" is ugly.
I don't look at people that way.
On the forum there are only those who know more and those who know less.
I classify myself as the latter, who know much less. It is not false modesty but a factual situation.
So don't take my works seriously. Rather turn to the works of smarter people here on the forum.

[ivconic]

The first thing I would change here is the TX.
I would replace the existing one with bipolar using H-bridge.
This will contribute to canceling the influence of the soil mineralization, and the EFE sample is then unnecessary (it can be used for something else).
I've been looking at the White's AF108 solution, I always go back to it because I like it. (It is not an H-Bridge, but it is a bipolar TX, more simply solved.)
Benefits? Advantage over VLF I/B? A big! In cases that I have described several times on various topics.
In short; a small gold or silver coin, covered with Ancient Roman ceramics; becomes absolutely invisible to most VLF I/B detectors and is always "iron-ish trash" to others.
As far as timing is concerned; it's good to look at the "math" that Joop explained on one of the older topics. Changing the timings is easy.
I'm quite off topic now, I'll try to "get into" the code and recall everything.
The detector will require the addition of one more channel... at least. A good example is Gold Scan.
No need to reinvent the wheel if someone much smarter than us has already done it. We should learn from their work.
I wasn't planning on doing this anytime soon... but now I'm motivated to slowly get involved again.

[Teleno]

Oh yeah... I don't pay attention to those things... my fault! You noticed well!



FQP3P50
IRF9530
IRF9640

tested all 3 btw...

...

A neurotically meticulous hair-splitter...

Only the truè insiders can spot and correct the intentional errors you plant in your schematics. They're made for the elite, the peasants is left with a dead board and scratching their heads. Devious!

[pito]

I think the pulse width 42 us is to big, I want to try half of that , how to change it ?
And delay regulation is to small ( 1 to 42 ), can you double it ?

[pito]

discrimination, aluminium and Iron, oscilloscope directly on coil.
https://www.youtube.com/shorts/ZuQNmoRR8Vk

to add GEB and possibly = need more info, (I'm ok with IB VLF detectors , this is my first PI) , I trying to figure out what benefits this kind of detectors are giving, I thout that they are not sensitive to ground and they do not need coil shield.


it is does not look that those coils have a shield.


later some kind of DISC... = watch video

[pito]

for now I replaced , Q2, Q3, Q5 by single logic gate MOSFET BSS138.

[ivconic]

Oh yeah... I don't pay attention to those things... my fault! You noticed well!



FQP3P50
IRF9530
IRF9640

tested all 3 btw...

...

A neurotically meticulous hair-splitter...

[moodz]

Later I made this, improved version.
I don't have video recorded.
Or maybe I have but I can't locate it on my backup disks... not sure.
It works alright!
These were rather "academic" attempts, step by step, to try everything in practice, before moving on to the next improvements.
I don't remember the details, I was doing a lot of different things at the same time and that's not good.
Losing focus. Then I put it aside with a plan to continue one day.
...
What you or someone else from the forum, with good will, could contribute to this thread; is to continue further, to add GEB and possibly later some kind of DISC...
I am planning it myself, sometime, when I have the conditions and focus.
I have no conditions at the moment, a very bad period for me.

How is that N type Fet symbol in the TX circuit working out for you ?

[ivconic]

And of course, something that I must mention without fail; Davor made a very significant contribution to the work on this version.
Without his help I would not have managed easily.

[ivconic]

A small note: I wrote the power supply 8.4-12v on the schematic, you should pay attention!
If a 7660 is used then the power supply should not exceed 10v.
In case of power supply of 12v and more; 1054 is the choice.
The 7660 will overheat and burn out.

[ivconic]

Later I made this, improved version.
I don't have video recorded.
Or maybe I have but I can't locate it on my backup disks... not sure.
It works alright!
These were rather "academic" attempts, step by step, to try everything in practice, before moving on to the next improvements.
I don't remember the details, I was doing a lot of different things at the same time and that's not good.
Losing focus. Then I put it aside with a plan to continue one day.
...
What you or someone else from the forum, with good will, could contribute to this thread; is to continue further, to add GEB and possibly later some kind of DISC...
I am planning it myself, sometime, when I have the conditions and focus.
I have no conditions at the moment, a very bad period for me.

[ivconic]

1) Don't remember, long time ago, close I suppose.
2)
3) Yes. Take "~50cm" with reserve, I never actually measured the distance.
But it is above 40-45cm for sure...

[pito]

The coil is 17-18 cm in diameter, 0.38mH, about 2 ohms. = 25 turns 0.5 mm wire ?
In the zipped file is the Sprint Layout of the pcb.= Thanks, I will go with SMD.
~50cm and that's when changes occur.= visible on pin 6 ?

[ivconic]

That pcb was scrapped, in the meantime I experimented with some things and I no longer have the pcb in its original form.
I have oscillograms, I can see from the date on the files that it was 2020.
It might be useful.
The first approach of the small pliers to the coil is at ~50cm and that's when changes occur.
The coil is 17-18cm in diameter, 0.38mH, about 2 ohms.
I initially made the coil for the FelezJoo PI and since then it has served me for various experiments in the workshop.
In the zipped file is the Sprint Layout of the pcb.

[pito]

Thank you, I'm thinking about building it.
I want to make some changes, replace the old operational amplifiers with an MCP6022, so that I can use single power supply.
It will be helpful;
1. Number of turns in the coil
2. video, oscilloscope on pin 6 of U2 (at what distance from the coil are visible changes on the oscilloscope for coin ?)

There is an idea to add discrimination.