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

[jladre]

Dear Jladre, thanks for your videos. II am building the felezjoo pi. If you can, I need information. which resistance and inductance needs to have the coil? which diameter it is better for discrimination? I can replace tantalum capacitors with electrolytic capacitors? thanks a lot Dabbo

Hi! You dont need to replace the tantalum because machine work best with it. For best result of coil for this machine used a stranded type wire..but solid wire also works you must do it in spider web style and maintain wire spacing in every turn to reduce capacitance, because this machine is so allergic to capacitance. Resistance may 350-400 uH.. Note: use lf 357 to achieve discrimination.

[jladre]

hi all

Can someone give me the
pcb

thank you

Hi pigeon..you can download the pcb at early page of this tread.

[Dabbo]

thanks a lot jadre, I do not find the tantalum capacitors, I hope it is correct the electrolytic ones. I seen on the net some felezjoo pcb with electrolytic capacitors. I use lf357. the next few days I will update you on my work. Greetings to all

[eclipse]

For the 2.2uF cap it must be low ESR. Low quality electrolytic might not be a good idea. You may try polypropylene (FKP2) cap.

[WM6]

Resistance may 350-400 uH..

You mean inductance.

And what is proposed resistance of coil?

[Dabbo]

Thank you very much eclipse. I own the 2.2 uF tantalum. For the moment I have not found C6, C12-100uF tantalum. and I want to replace these with electrolyte. greetings dabbo

[jladre]

Hi Dabbo! My board is also using electrolytic cap except for the 2.2uF.

[jladre]

You mean inductance.

And what is proposed resistance of coil?

Hi WM6! yes i mean inductance..i was just thinking something while typing.. Resistance for coil is not that critical just as propose..i tried different resistance and it work all from .7 ohm to 5.8 ohms..

[Dabbo]

jladre perfect. I then try with electrolytic 100 uF. thank you very much for helping

[jladre]

Here my video of felezjoo with 30cm spider coil 5.8 ohm resistance, 386uH inductance,.. Detect a scrap diode 1n4148 at 2 inches distance..
Please tell me if it is enough senstivity or need more??
https://m.youtube.com/watch?v=D9zGJOi9Wwk

[WM6]

For 30cm coil this is good results with your testing diode.

For double the distance on diode you need half diameter of such coil (about 16cm spider coil)

[ivconic]

I completed it recently, took it outdoor with me and performed detailed tests.
What can i say? It is useless on mineralized soils completely, if Sense is over "12".
It "beeps" all the time. There is no way to calm it down.
Than i discovered how to calm it down for a while; set Sensitivity to "10" (maximum is "20") and than switch it Off and than back On. It is "balancing" at start up and than it is calm for a while.
I can walk several meters and it remains calm. Than randomly it can produce short audio response, but generally it is not a problem. By lifting coil from a ground for few inches make it to calms down.
I tested it than on some buried targets. All targets are detected with success, though the same targets are also detected by Deus and Fisher's F2 and F4.
I tried to check the differences by lifting coils from the ground, above target spots, and FelezJooPI is detecting same targets better than F2 and F4, of course, but not better than Deus.
This means it is indeed sensitive and more powerful than ordinary machines like F2 and F4 are, but not significantly better than good machines as Deus.
And important is to emphasize that Deus was with 22.5cm coil while FelezJooPI was with 38cm coil, during those tests.
When testing it in the air and Sense is adjusted at "18" or even "20" ; than FelezJoo PI is absolutely superior even over Deus. It shows fantastic distances in air!
But on real soil... i am afraid it is far away from something we can call "excellent".
So, i guess good step forward would be to fix the issue with sensitivity. I guess it's because of huge amplification at front end. I wonder what would be if we lower the gain at LF357?
My 38cm coil is made from stranded wire and additionally i put Al foil "Faraday cage" on it, connected to pcb ground. Previously i tested it with same coil without "shield" and it behaved much worse.
Cable for coil is two leads, with common shield. I guess it's the most proper cable for this detector.
Conclusion; it can become decent machine, but right now is not. It has fatal issues with mineralized soils and too much gain at front end.
I guess Qiaozhi's anticipation from the beginning of this topic was absolutely right.

[ivconic]

Discrimination... no way! Not working at my device at all.
Randomly it can "discriminate" shallow Al foil by displaying "non ferro "on LCD and proper VDI number, but that's all.
I am using LF357.
It is not discriminating ferrous targets at all.
...
One more thing; those 1860 type batteries, 3.7V/"4200mAh" that i planned to use... USELESS!
I put two of those in parallel , giving again 3.7V but "2x4200mAh" and than those are supplying small DC/DC adjusted to 17.6V at the output.
FelezJoo PI worked with such supply for about 15 minutes! Ha,ha,ha!
Than in a moment those "17.6V" became "5.1V" and that's was all.
Completely useless those are. Especially on PI detector. Especially if those are "Made in China" and especially if those are rated over 1000mA.
C'mon! I suspected that earlier... just waited chance to check them on my own.
Rubbish!

[jladre]

I completed it recently, took it outdoor with me and performed detailed tests.
What can i say? It is useless on mineralized soils completely, if Sense is over "12".
It "beeps" all the time. There is no way to calm it down.
Than i discovered how to calm it down for a while; set Sensitivity to "10" (maximum is "20") and than switch it Off and than back On. It is "balancing" at start up

hi ivconic! You dont need to turn it off and on just for balancing pupose, the push button switch for "down" direction is also the balancing key. Just push it anytime and machine will balance

. And about the miniralized soil yes felezjoo is over temperament on that as what i also experience but i discover that it depends on your coil.. In my case also im using 5 pcs 3.7 li-ion battery mark as 6800mAh (about 4200mah real power) it works about 3 hrs of used before i need to recharge.

[jladre]

For 30cm coil this is good results with your testing diode.

For double the distance on diode you need half diameter of such coil (about 16cm spider coil)

Thanks WM6 i gonna try that