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Ok, maybe the same problem TDI tx pulse width 100uS and yours is 50uS. That is less power going to coil assuming the same Tx frequency and less sensitivity.
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The TDI is a hotter design, everything else equal (sample timings & GB) the TDI will always go deeper. At a minimum the TX is 100us and 3.2kHz which burns a lot of power. The BPI is a circuit whose purpose is to demonstrate basic GB so I chose a conservative setup to keep people out of thermal trouble. However, the GB mechanics between the TDI & BPI are the same, just done in different ways. You should be able to alter the BPI to mimic the TDI in terms of GB operation, with less overall depth. The preamp BW is part of the GB equation so it may also need changing.
When changing the TX width/frequency, probably what needs to be done is to also change the ground sample width to maintain the same overall GB range. I did not do that in the code but it should not be difficult.Comment
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Thank you very much, Carl and Altra, for your answers. I'll try changing the sample widths of the GNDN and GNDP channels and matching them to the samples of the TGTP and TGTN channels. I'll also change the sample times and set them to the same as the TDI. In short, I'll use the same time base as the TDI, and I'll also use a 3 kHz frequency and a 100 µS pulse width. I hope this works.Comment
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Hi Carl. Are these changes enough to change the width to 100us? I just don't know which ones I have circled in red and whether they should be 100us. Thanks.
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Just turn the GB pot fully to the side of the target channel.Comment
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Ok, today I found time to do some things.
First, I wound a 0.32mH, 27cm mono coil.
Second, I put a real cable between the coil and the pcb.
I asked a question about this before, I didn't get an answer. So I found the answer myself.
Third... the freq is now fixed at 2kHz.
I won't write further, because I'm tired and very lazy... don't get me wrong, these two videos don't even need special comments, for those who are "in the matter" any additional comments are unnecessary.
For those who are not "in the matter", even 10 pages of comments will not be enough.
Final conclusion: this is a very good starting platform for further development.
But more importantly, for learning. Carl did a very good job.
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Okay, a few things though...
GEB... even at the minimum ("OFF") it does not detect (does not react to) a piece of ancient brick... to which all VLF/IB detectors I have tried so far react very aggressively, when their GEB is not set (on some, even then, that brick cannot be completely rejected).
So in my case, what I have here; GEB as such is not even needed. Works perfectly even with GEB on "OFF".
BUT!!!
In my case, what I have here, with the targets displayed; For me, GEB behaves like a "DISC" between "colored" targets.
It is impossible to reject iron... but it is very noticeable and easy to see the rejection of certain non-ferrous alloys.
So... "GEB" in this case could be understood as "DISC" which has a certain range of discrimination of some targets and their TC.
Identical to what I saw earlier on the GS4 I was building not so long ago
Maybe I wrote this clumsily, vaguely, sometimes I have problems to write a thought clearly in English. But I'm sure you'll understand.
As for the "hole"... I haven't gotten to that yet.
I wanted to correct previous mess around the coil and the cable and then evaluate the real capabilities of the detector.
I think this detector will be very useful with the smallest coils, say 10-15cm in diameter, at most.
Exactly what I am primarily interested in.
However, I am still not satisfied with the behavior on the smallest targets of the "weak" alloys (an alloy with weak magnetic properties and poor conductivity)...
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Hello EduardoOriginally posted by eduardo1979 View Post
It turned out very well - well done.
What are these yellow cables for?
They are not here.
https://www.youtube.com/shorts/3mG-37O-b1QComment
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Carl, I don't know if I remembered and understood correctly from the book... but as you can see the audio behaves the same on both ferrous and non ferrous metals.
There is no difference in "wee-waa" or "waa-wee" (or however those terms are described).
Maybe I misunderstood in the book, but I expected the audio to behave differently.
I forgot to mention that I put all the original chips back on the sockets, now they are all TL071, 071 and 074. Tried with TLC didn't give any better results.
A couple of things I would like to see improved on this detector:
1) Much greater "depth" on coins (which was to be expected but did not happen)
Big coils and enormous "depths" on targets such as "barrels, tanks, airplanes" do not interest me in the least.
I am exclusively interested in coils with a maximum diameter of ~27cm.
2) Since GEB works fantastically (I really like it) and DISC doesn't exist, it would be nice if the audio made at least some noticeable difference.
I expected better results on coins at 2kHz and with minimal delay.
I said I wouldn't write too many comments, but I suffer from insomnia, so I deny myself.
What I didn't specifically point out is that the application of a quality cable from the coil to the pcb changed the behavior of the detector DRASTICALLY in favor of stability, purity of behavior, purity of sound, etc.
But still in the background of the sound, very quietly, you can hear a "thin" accompanying "buzz" sound. I assume that some part of the clock "breaks through" through the rails to the audio.
I also don't believe that choosing a TL07x type preamp is the best solution. But I have no idea at the moment what to replace them with. And even then, I'm sure the differences would be barely noticeable.
All in all, educational, instructive... it was worth the effort.
And is this a detector that I would go out into nature with?
Not for now.
In addition to Deus 1 and Vanquish 340; it would be redundant to try anything with this detector.
But... if the range was improved to very small coins; I'm SURE that this PI with a GEB like this would be unbeatable in some of my fields.Comment
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@ Eduardo;
Can you make a short video and show the detection range in the air on several different coins, preferably smaller diameters.
(please no rings, just coins)
What is the diameter of your coil? What PPS is your video set to? Delay?Comment
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You could do two things:Originally posted by ivconic View Post
1. To damp the coil correctly.
2. To place the target samples at an earlier time.Comment
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It's good that you mentioned that.Originally posted by boilcoil View Post
The 390 ohm damping resistor remained on the pcb from before.
With the new 0.32mH coil, I checked how it looks on the oscilloscope; looks perfect!
Just a coincidence, but I think this coil is perfectly "damped" right now.
And admittedly, it can be heard in the sound and behavior.
I didn't pay attention to what the minimum sample delay is. But I think it's good advice.
The question is only with the existing hardware limitations, what minimum sample delay can realistically be expected...
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