felezjoo PI(the best pulse induction metal detector that I made until now)

[Qiaozhi]

But... you can't earn even one cent on FelezJoo PI and that's what makes it undesirable to be promoted and built here among forum members.
While on the other side; CrosbowPI and MPP are yours "small and shy" projects (actually not your intellectual products but just plain copies of somebody's else ideas) on which occasionally you earn a buck or few....
And that's what is in root of the whole of this story that is going on here.
Spit on any idea "other than mine", discredit it in the very beginning and focus attention of forum members on something which will bring you a buck or two instead.
This is a trend that is clearly visible also on other similar topics too

We've been through these accusations before, so you are already aware that I make not one penny from any of these projects. On the contrary, I have spent my own hard-earned cash to bring these projects to fruition. Also, they are not "just plain copies", but are modified and improved versions of some classic designs. The projects you mentioned are well proven, and that's why there have not been any negative comments. On the contrary, there have been many positive reviews. To quote Socrates: "Envy is the ulcer of the soul.".

That's why i came here and am trying to put a new, more honest and objective light on this otherwise indeed splendid project called FelezJoo PI.
FelezJoo PI is just the very BEST small PI diy project on this forum, with no competition at all.
All other already mentioned diy projects here are just funny jokes comparing to FelezJoo PI.
Be a fair and live with it.

The Felezjoo has many claims attributed to it, and to be honest, some of these claims do not stack up. I am not the only one asking questions ... and that's just it "asking questions", not "spitting on" or "discrediting" the project in any way. In fact it should be a compliment to the designer that there is a high level of interest.

If the so-called iron discrimination is as good as is being claimed, then of course there will be questions ... lots of questions. From simply looking at the schematic it is clear that all is not as it seems. Personally I still think this is actually conductivity-based discrimination, otherwise how can you explain how it works? Or perhaps you don't care? When unusual claims are made, others become interested in the technicalities, and that's simply what's going on here. People only tend to get defensive and make accusations when there's something to hide. Also, you have side-stepped the issue of the misleading video demonstrating the single diode as a low conductivity target, which it definitely is not.

Anyway, back to the technical details ...
I have discovered through some SPICE simulations that the LF357 used in the preamp of the Felezjoo is faster than was expected. It is slower that the Surf-PI and the MPP (which has by far the quickest response) but is not quite as slow as at first thought. However, it's still too slow to explain the claims for low conductivity target detection (ignoring the diode demo).
As far as the so-called iron discrimination is concerned, it appears that I would need to experience that for myself to get any sense out of it, as emotion is starting to cloud the judgement of others.
The LF357 (by the way) is an obsolete part, and the few that are still available are very expensive. It has a GBP of 20MHz and slew rate of 50V/us, which is why the preamp is faster than expected. All the suggested equivalents are not exact replacements. The best one I could find is the AD745, with a GBP of 20MHz and slew rate of 12.5V/us.

So ... keep your hair on!
No-one is attempting to suppress this project. It's just that extraordinary claims require extraordinary evidence. Most engineers are a bunch of disbelievers until they can be proved otherwise.

[Qiaozhi]

Her is a short video on aluminum detection. A 5x6 mm aluminum foil folded into two is detectable at 3". A 1x1" aluminum sheet 50% thicker than soda can is detectable at 14-15". Note: it is just an air test. And it is all metal mode. Critics is accepted anyway thats not my problem
NOTE: i dont and never said that 1n4148 diode is a low conductive target. What i say is tiny target.https://m.youtube.com/watch?v=N3EeKpyZIEo

I'm pleased you accept critics, as you wouldn't last very long here if that wasn't the case.
By the way .. are you the designer, or perhaps a friend of the designer?

It's getting late here now, so I'll watch the video tomorrow, and most likely ask more questions after that.
And, hopefully, Ivconic won't jump down my throat again in a fit of emotion.

[jladre]

I'm pleased you accept critics, as you wouldn't last very long here if that wasn't the case.
By the way .. are you the designer, or perhaps a friend of the designer?

It's getting late here now, so I'll watch the video tomorrow, and most likely ask more questions after that.
And, hopefully, Ivconic won't jump down my throat again in a fit of emotion.

Hahaha!..please don't used your power just for that little things it unfair.

I just a hobbyst that fun on building md.. Is not that obvious that im not related of the designer of this md? If it could happen i will never keep on asking the full hex code.

[ivconic]

Envy?
Why would i feel envy about this?
There is no reason!?
In fact; i could be envy only on author of FelezJooPI, because he did good job, not me.
(At some point i am!)
...
Your "chronology" now extends to; "LF357 was considered slow previously and now is fast" !!!
And you may keep on going like this to eternity... instead i would like to see you built this detector and have it materialized.
Than you would be able to place here correct remarks and analyze.
Forget the simulator and simulations. Take the soldering iron and do something. (Beware not to burn your fingers with it!)
Somewhere you said "well proven"... well, this one is also "well proven" to us who made it and make it work nice.
Can't you recall that i also made MPP and recorded a video on it? It is not "well proven" for me because i didn't liked it.
And why? Because it was never finished project. You offered it here as unfinished thing so to have enough "material" to talk about in next 20 years, so it seems.
Be fair and don't put in the same line analogue projects like MPP with this one, this one is digital, having mcu & LCD, very rich and nice digital audio, lot of additional informations on the display, lot of adjustments and options.
And for what's most important; this one is working much better than MPP. In any aspect.
Only valuable info from all your posts on this topic so far is your elaboration on possible LF357 substitute. I salute that. That's the only thing that may contribute here.
And for the end; i have nothing especially against you personally. I rise emotions only when i see unfair and unequal treatment towards the projects and between people here.
Otherwise i really don't mind.

P.S.
LF357 as i recall was used in majority of high class PI detectors. For example it is used also in Pulse Star II and Pulse Star II Pro.
LF357 is still actual, not that hard to obtain, price is 1.3 euros here in local shops, and much lower at some shops abroad.
Only problem around it may be the reasonable suspicion on "rebranded" LF357 series , which are floating on some markets.

[Qiaozhi]

Hahaha!..please don't used your power just for that little things it unfair.

That wasn't a threat. I hope you didn't think it was one. My meaning was just that you mustn't take any questioning here too seriously, as occasionally some people get emotional, and the discussion turns into an ill-tempered row. I don't think either of us want that to happen. At least that was never my intention.

I just a hobbyst that fun on building md.. Is not that obvious that im not related of the designer of this md? If it could happen i will never keep on asking the full hex code.

Please don't take my interest in this project as "bashing".
It should be possible to have a grown-up technical discussion without the emotional responses. I know you haven't done that, which is good. Also, I was only asking about whether you knew the designer, or not, because this might make it easier to obtain some more indepth information. Personally I still have my doubts about the so-called iron discrimination. Not whether I'm really seeing it reject iron in a video, but more to do with whether the discrimination is based on target conductivity. I suspect this must be the case, due to the simplicity of the hardware, and the fact that it uses a mono coil. It's probably better that you don't personally know the designer, because this makes you more likely to be an independent and unbiased researcher.

So ... I've watched the video, and it certainly appears to be able to detect the 5mm x 5mm aluminium square consistently from about 2".
This is a much better test than the signal diode. By the way, I referred to the signal diode as a low conductivity target because of its small size. For example, in order of highest conductivity, silver comes first, followed by copper, gold and aluminium. Yet we often refer to small gold nuggets as a low conductivity target. This is basically due to the size of the target, and the fact that the gold is mixed in with other ores. An object becomes a low conductivity target when it cannot sustain eddy currents for more than a few micro-seconds..

I think part of the explanation for the better-than-expected response is the LF357 opamp. This opamp has much superior performance in this application than the usual NE5534. Unfortunately the LF357 is now declared obsolete and not recommended for new product designs, and there is no direct equivalent. The closest one appears to the AD745. The problem in obtaining this component is also made more difficult by the number of fake devices on the market. Let's keep investigating, and we'll get to the bottom of this eventually.

[Qiaozhi]

Your "chronology" now extends to; "LF357 was considered slow previously and now is fast" !!!

Actually I said the preamp in the Felezjoo was slow, not the opamp.
That reasoning was based on the preamp being configured for a 2000x gain. However (in this design) the LF357 offsets this disadvantage by having a much larger GBP and faster slew rate than most other opamps.

Can't you recall that i also made MPP and recorded a video on it? It is not "well proven" for me because i didn't liked it.
And why? Because it was never finished project.

The MPP is a finished and proven project. You can easily see that by reading the MPP threads, especially the Completed Projects section. This section only represents a small number of the MPPs that have been successfully built and used in the field. This is because not everyone wants to stand up and be counted, or to be in the rogue's gallery.

You offered it here as unfinished thing so to have enough "material" to talk about in next 20 years, so it seems.

As already mentioned, the MPP is not an unfinished project. Please read the MPP threads -> Minipulse Plus
If the project was an unfinished piece of work, then Silverdog would not have it on his website -> www.silverdog.co.uk

Be fair and don't put in the same line analogue projects like MPP with this one, this one is digital, having mcu & LCD, very rich and nice digital audio, lot of additional informations on the display, lot of adjustments and options.
And for what's most important; this one is working much better than MPP.

The reality is that I could easily add a micro to the MPP, and put in lots of bells and whistles, but that was never the intention. The purpose of the project was to update and modify the original Pulse Technology MiniPulse (an Eric Foster design) and give it a new lease of life. It was purposely kept in its analog format to make it an easy project to build. It still has the fastest preamp of all the other designs, including the Felezjoo. Anyway, this thread is not about the MPP, which has its own dedicated thread.

[ivconic]

...
So ... I've watched the video, and it certainly appears to be able to detect the 5mm x 5mm aluminium square consistently from about 2".
This is a much better test than the signal diode. By the way, I referred to the signal diode as a low conductivity target because of its small size. For example, in order of highest conductivity, silver comes first, followed by copper, gold and aluminium. Yet we often refer to small gold nuggets as a low conductivity target. This is basically due to the size of the target, and the fact that the gold is mixed in with other ores. An object becomes a low conductivity target when it cannot sustain eddy currents for more than a few micro-seconds..
I think part of the explanation for the better-than-expected response is the LF357 opamp. This opamp has much superior performance in this application than the usual NE5534. Unfortunately the LF357 is now declared obsolete and not recommended for new product designs, and there is no direct equivalent. The closest one appears to the AD745. The problem in obtaining this component is also made more difficult by the number of fake devices on the market. Let's keep investigating, and we'll get to the bottom of this eventually.

Now... that's more constructive approach!
It should be good to look up for more possible substitutions too... if any.
Because author himself also pointed out on delicacy about LF357.
Seems he adapted the code especially relying on LF357 features.. which is good and bad in same time.
Good because he pulled out the maximum from it; bad because this made whole design more delicate.

[Qiaozhi]

Now... that's more constructive approach!
It should be good to look up for more possible substitutions too... if any.
Because author himself also pointed out on delicacy about LF357.
Seems he adapted the code especially relying on LF357 features.. which is good and bad in same time.
Good because he pulled out the maximum from it; bad because this made whole design more delicate.

Yes, I agree.

[liudengyuan]

qiaozhi, hello, please tell delta pulse and pulse hammer their respective advantages, which detection range farther

[ivconic]

Actually I said the preamp in the Felezjoo was slow, not the opamp.
That reasoning was based on the preamp being configured for a 2000x gain. However (in this design) the LF357 offsets this disadvantage by having a much larger GBP and faster slew rate than most other opamps.


The MPP is a finished and proven project. You can easily see that by reading the MPP threads, especially the Completed Projects section. This section only represents a small number of the MPPs that have been successfully built and used in the field. This is because not everyone wants to stand up and be counted, or to be in the rogue's gallery.


As already mentioned, the MPP is not an unfinished project. Please read the MPP threads -> Minipulse Plus
If the project was an unfinished piece of work, then Silverdog would not have it on his website -> www.silverdog.co.uk


The reality is that I could easily add a micro to the MPP, and put in lots of bells and whistles, but that was never the intention. The purpose of the project was to update and modify the original Pulse Technology MiniPulse (an Eric Foster design) and give it a new lease of life. It was purposely kept in its analog format to make it an easy project to build. It still has the fastest preamp of all the other designs, including the Felezjoo. Anyway, this thread is not about the MPP, which has its own dedicated thread.

To cut the story and stop with further unnecessary debates and to focus only on topic here; i shall say only this:
at first i liked MPP idea much. That's why i decide to make it. And it works from the very first switching ON.
But audio was awful and "depths" was not what i expected. There could be many reasons for that, on the first place i could done something wrong. Than i saw it grows into "versions" and "versions" and in time i lost interest and focus for it.
As i previously somewhere wrote; i am not saying those are bad. I am only trying to make the difference between all those mentioned so far and this one.
Because this one is "digital". Not just plain "bells&whistles" but indeed digital. Minimalism in components and all the processing done by MCU. That's not what we may call plain "bells&whistles".
This is what makes it special and much different than other diy projects we've seen here so far. That's what makes it "category" on it's own here.
And that's why i think is necessary to pay especial attention on it and give it a chance.
Otherwise... apart from that; all my respect also goes equally to all other honest diy attempts and ideas too.

[Qiaozhi]

Just a quick thought ...
Has anyone probed the TX waveform with an oscilloscope? In an early post in this thread koohyar made a statement that the Felezjoo works in the same way as the Minelab GPX. I'm wondering whether this implies that the Atmega micro is automatically varying the TX pulse width. If someone could look at pin 16 of the Atmega, that would show us what the TX oscillator waveform looks like.

[ivconic]

Just a quick thought ...
Has anyone probed the TX waveform with an oscilloscope? In an early post in this thread koohyar made a statement that the Felezjoo works in the same way as the Minelab GPX. I'm wondering whether this implies that the Atmega micro is automatically varying the TX pulse width. If someone could look at pin 16 of the Atmega, that would show us what the TX oscillator waveform looks like.

I may do that.
Recently i got this as a gift from a friend:
https://www.poscope.com/PoScopeMega1
Still adapting on it.
Neat little thing!

[ivconic]

I just did it and you'll be amazed to see it.
Just waiting upload to Youtube...

[ivconic]

Uploading is annoying...
You'll notice that i've changed sampling frequency few times...

https://youtu.be/EAlLdygdf5g
https://youtu.be/tVMJxeS_FNE
https://youtu.be/KyYgWym_ZOs

[Qiaozhi]

Yes, that's very interesting. As far as I can tell from your videos (especially the last one) the pulse width doesn't seem to change, but there are discrete gaps between the pulse chains. I'm not sure whether this has any significance, or simply that the TX oscillator goes off while the micro is processing data.