Years before I put up together a PDF explaining my (at the time) methods.
Then some time later Don Bowers made even better PDF with more details.
Nothing much significant changed in the meantime, principles are the same.
Except that now I have better conditions and 3D printers, so...

I know the features are provided by Sash, I was just wondering what kind of coil winding mechanism you developed.
I guess I couldn't explain myself.​

Sure, no problem, but I still don't have a solution.
I'm still thinking about coil 3D drawing and printing..
When I come up with something I'll post it here.
...
As far as coil specs; Sasho already gave the specs:

​​...

Thank you very much...

The schematic kt315 posted looks correct. For the DD coil I would use

TX = 300uH 2Ω
RX = 300uH 2Ω-10Ω...

Hi all,

this is what I mean with limitted gap region in the coil bundle for the capacitors.

Top-View:

You can see, that the other regions don't have a gap in the coil bundle. It is as large as necessary to place the capacitors there. + same gap to the windings...

Thanks,dear Carl,do you have schematic and DD coil instruction?do you doing reverse engineering this detector?

Hey, do you have a chance to share the file for the print you made for the iconic coil? I'm thinking of printing it too.
Can you share with us how you do the coil winding part? I'm curious about how you wind your coil.​

GS4 --> GS5 --> TDI --> TDI-SL

I did the TDI-SL, not the TDI. They are all very similar.

hello amigo
this is a product by Eric Foster and Carl. because you see a convergence to GS4. but my word here is last so let Carl to tell you more.

Oh man!,

how to solder a NP0 (C0G) SMD capacitor with 1.0 mm x 0.5 mm dimension?

I think the SMD 1206 (3.2 mm x 1.6 mm) is easier to handle. Even a 2 mm x 1 mm should be feasable.
As I have a ribbon cable with 10 strands, each strand will have it's...

Hi kt315,Thank you very much for reply,does a information about making DD search coils?and does a schematic is correct ?do you have pcb file?schematic is very close to gs4.4 sample .
thanks.

My 3D printer has a working volume of 220x220x250mm. But in practice I always use 200x200 bed area.
Ideally would be to 3D print the "OO" coil housing...200x200mm.
But how do I know the exact overlap area in advance?
For precise balance.
Maybe Aziz could help with his...

That's right.
However, now comes the most difficult part: designing the box, making the coil... phew!
I haven't DIY coils in ten years... I avoid that boredom, I mostly used stock coils.
But this time I'll have to DIY the coil anyway...​

......

Hello everyone:I am looking for schematic of TDI metal detector.
does anyone have schematic and DD coil information of white's TDI metal detector?
Thanks...

Hi all,

yep, even my old SMD capacitors perform very well. I don't know, which material it has. But a Q of 3000 at least. With very low ESR.
I can't believe it. But the real LCR measurement doesn't lie.

So, I'm going to buy a set of tiny NPO SMD capacitors soon. And the...

Hi all,

I will also buy a set of NPO capacitors soon. They could even be much better (temp stable, low ESR, rel low D). And very very small. Perfectly to sit in between the coil bundle wires. Paralleled to form a thin string of pearls....

Thank you for your work ...

Hi Zoz,
This project is in continues development last year. Me and GeoMax make many efforts to develop this serious PI project with standard PI DD coil (for Minelab GPX and White's TDI MD) and with possibility to Ground balance and real FE/non-Fe discrimination. I hope, very soon we will be capable...

And now we are waiting for the results in real soil. The tests in the air are good - as ivconic said - every proposal must show 3 things: a schematic, a PCB design and a video in real conditions to be properly evaluated.

​...

Without any adjustment, without turning the potentiometer, as I soldered everything - I immediately turned on the voltage.
Works like a charm from the first switch on.
Now I am definitely motivated to devote myself to coil making.
This is very promising!
Well done Sasho!
...

Hi all,

we have finally found an elegant way to "hide" all the capacitors even in inside a thick mono coil bundle made of plain standard ribbon cable. And the capacitors will be nicely shielded with the whole coil bundle too. Yes, the capacitors needs to be shielded as well. And...

Thank you so much Aleks85 for the details!

Practically any PIC you want, as long as it has enough pins. Peripheral register may vary a little bit, and if you use a lower speed device it will affect timing resolution....

That's why I said I don't have that many tools, and I don't have that much money either. I've worked in agriculture, as a bricklayer, and other jobs, but now I'm a mechanic. I'm not a technician, but I've never stopped studying, and if something interests me, I study it. That's why I've learned about...

No problem, I'm from Bulgaria, I can send you the Carl​'s​​ board and the chip programmed , but the video shows Eduardo's board, I don't have that variant....

and finished compact design, you don't like also?
​​...

I don't like that design, and in fact, the design I'm using is specifically for testing because it's well-designed and can be programmed directly from the board. It's worked for me, and to be clear, I didn't design it, but I like it, so I'm using it. I don't like your design, and I hope to use it during...

Hello i want pcb of this project ...

@Boadil
Glad you still like it 10 years later.
You could still improve it:
- adapt the main slicing level of the comparator with an an analog ground sample to introduce some sort of automatic GEB
- port it to a newer Microchip microcontroller
- preferably one with an internal...

Ah, it just happened that way.
For the first time since 2018 (since I have 3D printers) I switched from PLA to PETG and right at the start I had huge problems with the settings in Cura.
I think I'll go back to PLA when I use up this roll of PETG.
The final box looks good, but it needed...

your design = lot of wires = old fashioned
and modern design = almost no wires
​​​​​...

By the way, this is the motherboard I'm using. You can see it has small changes, but it's there....

https://www.google.com/search?q=LF35...hrome&ie=UTF-8
I will use modern 5V MCP6022

Hello Karl NC
Which chips can we port the code to?

PIC16F18426...

I have bad news. After using it for a while, it seems the LF357 was indeed damaged when the 7805 burned out. Now the debugging values ​​are far below the specified values, and therefore the discrimination isn't working properly. For the LF357 to function correctly, the values ​​need to be accurate,...

Yep, this idea is novel.
Leaving a limitted region gap for placing the parts in the coil housing, where the magnetic field strength is low at this gap region and hence produces less eddy currents by the parts placed in the coil.
Hurry up Donald (my best mate), we need to file a patent...

Now there is a magic trick, where we can leave a gap region to place the capacitors. This region is limitted to the whole capacitors volume space. In other regions, there won't be any gap.
To show this, I have changed the wires to single line wire model. So you can see, where the region is....

FERRO. Copper, gold, and silver are marked as NON-FERRO on the screen, making identification much easier. = it is not easier using LCD, easier is different sound...

This is the gap between the coil winding bundles with the ribbon cable mono coil.
...

Hi all,

what about my ribbon cable mono coil? Where to place the capacitors?
Ribbon cables can't be wound arbitrary. Best to do it as a spiral wound, which isn't best solution for coil capacitance. This isn't critical if operated in VLF mode however.
We have to divide the mono...

...they are persistant .. Nokta is battling them here :

https://ipsearch.ipaustralia.gov.au/patents/2023204592

this patent is trying to lock up bipolar constant current sensing till 2044....

Well...
what do you know...
I thought; who will now wait for the components, it will take a few days for them to be ordered and arrive at the address.
I went to the attic and found everything I needed.
The PCB is finished, but I'm quite exhausted, because I'm no longer in shape....

I've been following you, the discrimination works really well. ...

I am Turkey

The patent lists alternatives/combinations of the damping element that do not improve on the constant current sink, which is optimal, and therefore they defeat the stated technical effect.

Only a current sink gives non-exponential discharge. It forces the back-emf voltage at any given time...

Hi all,

where to place all the capacitors in the coil housing of the mono coil VLF?
A place, where the magnetic field is quite low would be optimal.

There is one good possible solution. Two solenoids connected in series, as basket weave winding to lower the coil capacitance...

They basically repackaged your patent, to put it mildly.
After al the obscurong legalese what remains in clear engineering terma is your idea:

The Active Element: A Controllable T/R Switch
Instead of relying solely on a static resistor, this invention uses the transmit/receive...

Hello, no, nothing, no sound, and just smoke! I've decided to desolder the PCB and start all over again! I'll need new components. This time, I'd like to learn the assembly and testing steps. It's difficult when you don't have a real background in electronics. A simple assembly is easy; I've built two...

Not at all...
The 2D/3D drawing on the JLPcb website sometimes does not reflect reality.
I have a lot of experience with those web displays so I wasn't too worried about what would happen on a real pcb.
​...
Damn capacitors!
I always miss them.
I have "tons"...

GEB is basically and change in the detectors zero reference level. To speed up this adjustment individuals generally move the detectors up and down to regenerate a larger difference voltage which aids in resetting the zero reference level a bit faster. Generally this is done automatically through design,...

Its hidden away in patent US9829598B2. .... note the expiry date of this patent
No I am not using a TIA just a straight 40 db low noise amp .. the bipolar TEM relies on reciprocal energy conservation .. or "ping pong" using a high inertial factor ( in this case a big inductor )....

This is the first test to demonstrate some of the discrimination capabilities of this detector.

By the way, this is a PI metal detector with the ability to discriminate metals by conductivity. It can be used to search only for more conductive metals like copper, gold, and silver. It's still...

Colleague haylaz0036, where are you from? I can sell you Carl​'s board and I will program it for you and sell it with the chip, no problem.

This is the first test to demonstrate some of the discrimination capabilities of this detector.

By the way, this is a PI Metal Detector with the ability to discriminate metals by conductivity. It can be used to search only for more conductive metals like copper, gold, and silver. It's still...

If it uses the same source code as the ITMD3 circuit, then all the code is in C and you can download it from the ITMD3 forum. Then you can port it to whatever processor you want. If you don't know how, then this is an excellent opportunity to learn....

I'm currently missing a few final materials; I'll get them, make the final touches, and share my test video with you....

I'm sorry, but I can't help you with the programming, as I have no experience with PIC microcontrollers and programming isn't my strong suit. There are many people on the forum with extensive programming knowledge....

Hello, how is the project going...?
...

I can't - I don't have that experience...

...

Mr. pechkata, could you perhaps recompile the .asm file on a different, more up-to-date chip?
...

This hex file only works on this chip...
Eduardo cannot answer....

I started soldering the components.
And like Murphy's Law ... I'm always missing some trivial components!
I will have to order them and wait a few days.

​​...

Dear engineer Eduardo, could you please recreate the hex code on a modern Jeep from 1979 that has easy access to the system? Could you please regenerate the hex code?

The PIC chip is used as a timing generator, so just about any other PIC chip will work....

Interesting. Care to share the patent number?

I think ground balance is better left to DSP. The loop keeping the coil in a "superdamped" state is already challenging enough.

These problems can be avoided as in the schematic above.

At the end of damping...

Hi all,

it is high time, to change the bad clips and wires of the basic passive sound card LCR meter. This has an huge impact for accurate measurements.
I should look for the other LCR meter breadboard. It has active j-fet buffers (dual op-amp voltage followers) for much more accurate...

Hi all,

I am very delighted about the MKP10 capacitors.
They have lower ESR (half) and very low loss factor D compared to FKP1 and FKP2 capacitors.
I have found much more MKP10 capacitors in my box. But I'll focus to low capacitance and low voltage ratings this time...

Dear engineer, what alternative could I use instead of the PIC16F18426 chip? I couldn't find one. What are the possible replacements?...

Big big surprize!

I have found a bunch of WIMA MKP10 capacitors:
Guess what!
Even they are metalized film capacitors (not foil), they have very low D and high Q. Some of them outperforming FKP1 and FKP2.
They are available upto very high voltage ratings.
And they...

Hi all,

can the AI fix a code, even there is no obvious bug in the code? Yes, it can fix it to have more bugs thereafter. If you persist on saying, that there is a specific bug there.
This happened to me. There was a sign bug in the old Lock-in demodulator. I was feeding the...

... the original purpose of the current damping servo loop was to improve the damping speed of a monopolar PI over a conventionally damped PI and it does this ( there is at least one active patent still covering this today ... not mine )

However the damping loop can become messy and the...

Yes - here the discriminator only works between gold and iron...
It doesn't work properly on other alloys...
...

Dear Eduardo, I really liked the detector and I want to make the sound perfect, but I can't find the PIC16F18426 chip. Is there an alternative, or could you please compile the hex file to an easily found BIP chip? Sincerely, [email protected]...

Hello.
Yes. This is a redesigned project I created, based primarily on Carl's Bipolar-PI design (ITMD3). The detector works quite well. As Altra correctly points out, I changed the VCO, the absolute value amplifiers, split the preamplifier into two stages, and added four level translators, replacing...

According to the tests I've run, its discrimination is based on conductivity. It's not precise, but it's capable of removing impurities and leaving precious metals like copper, gold, and silver. However, it can't differentiate between them; the discrimination only goes that far.

And in...

The vco and absolute value amplifiers have been changed. It is Carl's Tx and RX and Eduardo's (GS5 Lite) audio. Probably a nice project.

It doesn't just look the same - it is the same.

That looks like Carl's circuit from ITMD3

https://www.geotech1.com/forums/foru...olar-pi-design

https://www.facebook.com/share/v/18oMJhhkz7/


What are your thoughts on this device? I want to build this device but I can't find a PIC16F18426 chip. Is there an alternative chip that can replace it?...

Maybe not the right moment and place... but then again; maybe it is!
TGSL, at one time the most DIY in the world, no doubt about it.
Somehow, in 2004 I got a bad copy (scan) of a Tesoro Golden Sabre hand drawing by Bill Lahr from somewhere.
Among a few things, I made sure to put that...

Thanks for your note, Ivconic. We are definitely talking about the same guy. Bill had a ton of patience especially with the questions of a novice. I dont have any contact with the family but it's true--many of the detectors that I was looking at and using over the years--he had the schematics for. Everyone...

Yes, I built a Whites on this board. I used an AD548 input op amp, which is the best alternative to the LF441, and I used an LF444 instead of the LF347 – everything worked perfectly. It's hard to find high-quality ICs in my region, which is very important. It's also important to set the exact frequency...

Thank you so much, Aleks85, for sharing with us all!
Have you built the IDX Pro using this PCB?
If so, what details should I keep in mind to successfully build it?​

I'm doing some tests with the Felezjoo, but it's a version I've adjusted and I call it DW. I've also changed how it discriminates; now it can reject metals like lead, aluminum, pewter, soda bottle caps, and others, which go into the FERRO category, while copper goes into the NON-FERRO category. In theory,...

The box is legendary, well done!

Yes, same guy. Those alone were a huge contribution, and a lot of work on his part....

May God have mercy on her soul.

My deepest condolences to family and friends.
If it is the same Bill Lahr who manually drew countless schematics of various models of metal detectors; then that name has a very special meaning in my mind.
My first introduction to the world of DIY metal detectors was based on his hand drawings....

Bench tech legend and SMPI co-developer / patent holder Bill Lahr passed on last Friday. Bill did over 500 trials to refine the Surfmaster circuit to create a stable, deep, super gold sensitive pulse detector that found hunters huge amounts of gold over the years. He also held patents on features for...

A friend from Greece sent me the original LF357 and now the situation is much much better!
Coil is still not ideally made. A much better coil can be made.
But even with such a deficient coil; the detector now shows good potential.
However, I don't have any plans with the FelezJoo PI....

Apparently they now use the same die. So they are exactly the same.
​​
https://e2e.ti.com/support/audio-gro...ymatch=ne5532#...

Thank you very much Aleks85

Hi all,

well, I can work with Claude Code with minimum settings (low effort mode).
It is better than waiting and not getting any answer.
It fixed the LCR meter code for me finally.
Aziz...

Hi Paul,

this is really nice, the more KISS, the more ...

sch...

yup. Surfmaster II has some variations of pins matrix. nothing more. one board for all models. it was hard way i got the board pics on my email. i longly told a men how to use the light
for best photos....