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?

[Qiaozhi]

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I look forward to your test results George. 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.

Crikey! That would be a challenge.

[Qiaozhi]

Tend to disagree!
I just cut two square pieces of cola can; 6mm and 10mm.
10mm is easily detected at 3-4cm distance while 6mm is barely detected at 1cm distance.
But this is tested with completely inadequate coil!
We must agree that those are presenting very "specific" targets and demands "special" coil.
So, if we gonna split the hairs further; i plan to make such coil, just to prove that it is able to detect such targets.
I will only need some time to do that, because right now i am buried with obligations.
On the other hand; obviously this detector is not designed especially for such targets and certainly can not compete with dedicated detector.
Any dedicated detector for such targets will easily outperform this one, no doubts in that.
But also saying that "it can not detect such targets" is not true.
Though i will need additional info; at what distances of detection this will be accepted as "it can do"?
Give me distance and i will make adequate coil and test it asap.

[ATTACH]35901[/ATTACH]

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.

[baum7154]

The chances of the Felezjoo being useful for sub-gram gold are zero.
I am in the process of carrying out some tests on this detector, and will publish my findings in the near future.

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I look forward to your test results George. 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.

It seems clear to me that Ivconic is correct that he needs to build a fast coil in the range of 300uh in order to have a chance of detecting this target. Still I have not found a screen shot of the preamp output showing that its saturation will get out of the way in time to reliably detect fast decay targets.

Regards,

Dan

[jladre]

The chances of the Felezjoo being useful for sub-gram gold are zero.

It is a BIG false!! felezjoo is better compare to a hundreds of machine out there but it cannot compete to those machine design for that sub-gram gold. The point is fpi can see that tiny gold but in a short distance.

[jladre]

[ivconic]

I am forced to use a laptop with Win 7
what works for me is a blank 328p in a UNO board with a USBasp plugged into ICSP connector with pin adapter useing Eztreme burner software with USBasp drivers

This page is interesting:

https://www.hackster.io/rayburne/avr-firmware-duplicator-115d8f

[6666]

good morning to all, i built felezjoo circuit, but i dont know to program ATMEGA328P. I have breadboard, usbtinyisp and all components.
There is a tutorial that shows how to load hex file on atmega? tanks to all Dabbo

I am forced to use a laptop with Win 7
what works for me is a blank 328p in a UNO board with a USBasp plugged into ICSP connector with pin adapter useing Eztreme burner software with USBasp drivers

[ivconic]

"...The pre-amp is single-stage with an enormous gain to offset the fact that the design uses direct sampling with a 10-bit ADC..."

This is the problem that prevents you to accept different facts.
What if offset is taken into care by code and what if there is very special reason why LF357 was chosen precisely?
On the other hand; yes it is true: there is not much room to maneuver.
Yet a little water can still be squeezed out of dry beech!

[ivconic]

The chances of the Felezjoo being useful for sub-gram gold are zero.
I am in the process of carrying out some tests on this detector, and will publish my findings in the near future.

Tend to disagree!
I just cut two square pieces of cola can; 6mm and 10mm.
10mm is easily detected at 3-4cm distance while 6mm is barely detected at 1cm distance.
But this is tested with completely inadequate coil!
We must agree that those are presenting very "specific" targets and demands "special" coil.
So, if we gonna split the hairs further; i plan to make such coil, just to prove that it is able to detect such targets.
I will only need some time to do that, because right now i am buried with obligations.
On the other hand; obviously this detector is not designed especially for such targets and certainly can not compete with dedicated detector.
Any dedicated detector for such targets will easily outperform this one, no doubts in that.
But also saying that "it can not detect such targets" is not true.
Though i will need additional info; at what distances of detection this will be accepted as "it can do"?
Give me distance and i will make adequate coil and test it asap.

[Qiaozhi]

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Thanks George that explains why the large long sample delay targets. So I take from this that the detector is not useful for sub-gram gold but can detect coins, rings, bottle caps, nails, and probably buried pipes. I wonder what the minimum useful sample delay is considering the single stage high gain amp. Has anyone posted a screen shot of the amp coming out of saturation?

The chances of the Felezjoo being useful for sub-gram gold are zero.
I am in the process of carrying out some tests on this detector, and will publish my findings in the near future.

[Dabbo]

good morning to all, i built felezjoo circuit, but i dont know to program ATMEGA328P. I have breadboard, usbtinyisp and all components.
There is a tutorial that shows how to load hex file on atmega? tanks to all Dabbo

[baum7154]

It will not be able to detect a 6mm square of soda can. The pre-amp is single-stage with an enormous gain to offset the fact that the design uses direct sampling with a 10-bit ADC.

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Thanks George that explains why the large long sample delay targets. So I take from this that the detector is not useful for sub-gram gold but can detect coins, rings, bottle caps, nails, and probably buried pipes. I wonder what the minimum useful sample delay is considering the single stage high gain amp. Has anyone posted a screen shot of the amp coming out of saturation?

[Altair]

Hi Altair
When you construct the coil structure, wafer or spacers you might consider the attached website for a choose of material. It has a table of dielectric material constants. Air, Styrofoam, paper, dry wood and Teflon all have low dielectric constants.
Have a good day,
Chet


http://www.csgnetwork.com/dieconstantstable.html

Thank for references, Chet!

6666,
I will share my coil build design when ready!

[Qiaozhi]

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I am curious why so many videos use such large targets to demonstrate detection capability. How about you demo that quartz crystal can by the display in your video. Better yet please demo a 6mm square of an aluminum soda can wall. I'm just curious about the small metal item sensitivity and the test demos I have seen don't show it.

Regards,

Dan

It will not be able to detect a 6mm square of soda can. The pre-amp is single-stage with an enormous gain to offset the fact that the design uses direct sampling with a 10-bit ADC.