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

[green]

Including an updated target time constant list. Need to finish some and could add a couple. A 6x6mm can has a time constant of 1.5usec, 10x10mm can 2.4usec. The can targets are larger than nuggets but they have a shorter time constant which might make them harder to see. I've read where the coil circuit should be 5 times faster than the target. What about the preamp? Does a slower preamp filter the response giving more signal at say a 10usec delay?

[geoscash1]

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It would be great if this detector could be proven to see a 6mm square of soda can side wall at 20 cm buried in soil. Then I would build one.

Hi Dan,

Is there actually a video of any DIY MD picking up a 1/4"x 1/4" piece of soda can at 7.87 inches buried in the ground, Just asking because that to me seems a very tall order.

I have been working hard on one of my project MD's and fine tuning it (CBSII board) and am now able to pick up a real nor cal sub gram nugget (in air tests) at approx 3 inches but doubling that and in ground, now that would be a feat to be seen and I'd build it as well....lol

[baum7154]

3" is pretty good, but what is the weight of your nugget and what size and shape of a coil are you using?

Ivconic wanted a distance for the 6mm square target and I gave an ideal number. At times one must aim higher in order to do well. Lets see what Felajoo can do on this target even in air.

Regards,

Dan

[green]

Think I've seen a chart some where comparing coil size that shows the highest signal strength is when the target is at the coil radius. A smaller or larger coil would have less signal at that distance. If I'm looking at it right the best coil size to see a target at 200mm would be a 400mm diameter coil.

[ivconic]

A 10mm square of aluminium can is a much larger target than sub-gram gold.
Also - and perhaps I've got this wrong - but did you not state somewhere that you have decreased the gain of the preamp in your version?
Maybe the choice of pre-amp helps, but it would more interesting to see a video with the Felezjoo actually detecting a real sub-gram gold nugget.

No you are not wrong; at one of my previous detectors (made 3 so far, 2 already gone to my closest friends) i did exactly that. Reduced gain by decreasing 1M to 800k (470k + 330k i series).
Must admit that it affected only Sensitivity adjustment range (for example; with 1M Sens at "12" is the same as with 800k Sens at "15" or so).
Maybe there are other differences ... but i haven't noticed them.
...
Strictly rhetorical and abstract from my point of view; to achieve sub-gram gold nugget with FelezJoo PI would be indeed tough task. It will need dedicated coil and lot of playing with adjustments to see if that is possible at all.
I can't tell right now is it possible.
I accepted the FelezJoo PI idea at very start as "deep" detector for locating medium&large sized targets in soil. Obviously to work with larger diameter coils. My 38cm coil is actually a "small" coil for such task.
And having all that in mind; i am very satisfied with what i achieved with it so far. I am literally happy with it.
Why i support claim it is "the very best"...? Simply because it is indeed very best so far, among all other diy's we are having presented here on Geotech forums. Very best and without competition.
But it will most probably not be "very best" on such targets as small gold nuggets are. For such task one may turn to $x0000 Minelab products.
...
Yes it is very true; 6mm square cut from soda can and 10mm square cut from soda can are MUCH different targets! I wasn't aware of that until today.
I was not aware of that simply because i never really was interested to make PI for such targets. I am having Deus which is quite enough good in such rare cases.
I don't have such finds at my local terrains, that's why i am not focused on those at all.

[baum7154]

Think I've seen a chart some where comparing coil size that shows the highest signal strength is when the target is at the coil radius. A smaller or larger coil would have less signal at that distance. If I'm looking at it right the best coil size to see a target at 200mm would be a 400mm diameter coil.

------------------------
Hi Green,

I think I agree with what you have said and to clarify, the round coil is most sensitive at its center, one coil radius out from the plane of the coil. Is that what you are saying because this has been my experience? By this logic a 40cm coil would have the best strength at 20cm of depth but would have a difficult/impossible time of seeing a 6mm square of soda can unless Felajoo has some extraordinary capabilities of which we are not aware.

Dan

[ivconic]

Crikey! That would be a challenge.

None of the $x0000 Minelabs i've seen so far are not able to do that either.
It's complete overkill in demands!
C'mon!

[ivconic]

3" is pretty good, but what is the weight of your nugget and what size and shape of a coil are you using?

Ivconic wanted a distance for the 6mm square target and I gave an ideal number. At times one must aim higher in order to do well. Lets see what Felajoo can do on this target even in air.

Regards,

Dan

Dan you are pulling our legs here!
C'mon!

[baum7154]

In all honesty if Felajoo is the 'best' I would like to see what the best it can do is on a real world 6mm square of soda can target with no boundaries on depth, just actual results with the best coil you can build.

Regards,

Dan

[Qiaozhi]

No you are not wrong; at one of my previous detectors (made 3 so far, 2 already gone to my closest friends) i did exactly that. Reduced gain by decreasing 1M to 800k (470k + 330k i series).
Must admit that it affected only Sensitivity adjustment range (for example; with 1M Sens at "12" is the same as with 800k Sens at "15" or so).
Maybe there are other differences ... but i haven't noticed them.
...
Strictly rhetorical and abstract from my point of view; to achieve sub-gram gold nugget with FelezJoo PI would be indeed tough task. It will need dedicated coil and lot of playing with adjustments to see if that is possible at all.
I can't tell right now is it possible.

The claim with this design appears to be that a single-stage preamp with a gain of around 2000 (using the LF357 opamp) is as fast as a dual-stage preamp using an NE5532, and an overall gain of 1000. Undoubtedly the LF357 is a faster opamp, and this could be useful for other designs, but I'm struggling to see how the Felezjoo could possibly detect sub-gram nuggets. Even reducing the TX pulse width to say 50us, and using a fast coil with the correct damping resistor, there's no way I can see that it will be able to sample early enough to detect something with a time constant of about 2us. However, this is likewise a somewhat academic point for me, as like you I have no sub-gram (or even larger than a gram) sized nuggets anywhere in the vicinity of my home.

[ivconic]

In all honesty if Felajoo is the 'best' I would like to see what the best it can do is on a real world 6mm square of soda can target with no boundaries on depth, just actual results with the best coil you can build.

Regards,

Dan

As posted earlier, so far 3-4cm on 10mm cut and barely 1cm on 6mm cut.
Far cry from what you noted; 20 cm in soil or in wall... whatever, 20cm would be hell of result!!!
...
This is itchy for me, i will take Deus now to try on those cuts!

[ivconic]

The claim with this design appears to be that a single-stage preamp with a gain of around 2000 (using the LF357 opamp) is as fast as a dual-stage preamp using an NE5532, and an overall gain of 1000. Undoubtedly the LF357 is a faster opamp, and this could be useful for other designs, but I'm struggling to see how the Felezjoo could possibly detect sub-gram nuggets. Even reducing the TX pulse width to say 50us, and using a fast coil with the correct damping resistor, there's no way I can see that it will be able to sample early enough to detect something with a time constant of about 2us. However, this is likewise a somewhat academic point for me, as like you I have no sub-gram (or even larger than a gram) sized nuggets anywhere in the vicinity of my home.

That's my situation too.

[ivconic]

As posted earlier, so far 3-4cm on 10mm cut and barely 1cm on 6mm cut.
Far cry from what you noted; 20 cm in soil or in wall... whatever, 20cm would be hell of result!!!
...
This is itchy for me, i will take Deus now to try on those cuts!

18kHz, GMP program at Deus (Sens at 96):

- 6mm cut = ~12cm in the air.
- 10mm cut = ~16cm in the air.

Illustrative enough. It's not expectable any of the known diy's to beat that.
So finally; i don't expect neither FelezJoo PI to reach or beat that too.
Tough!

[seadoggy]

Hello mates,can i use this programmer to program AtMega 328P??

Thx and Regards.

[ivconic]

Hello mates,can i use this programmer to program AtMega 328P??
[ATTACH]35915[/ATTACH]
Thx and Regards.

Absolutely!
All the infos are here:
http://www.fischl.de/usbasp/