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

[smit22]

I have tested many reels and several types of cables. One 20 cm spool with automatic delay. 10.13.16.18.20.22.26.30.35.38.42.with the same parameters .. 10 to 20 days delay I got the same distance is about 34cm With coin coin. And 27cm with a gold ring. But with a delay of more than 30 as 38, the rejection does not work and the detection distance is 19 cm with a coin. But the delay of more than 20 is better Under the sole than less than 20 delays

[smit22]

Https://www.youtube.com/watch?v=UxttKqLFC4o

[cvele]

Nice work smit22!
I prefer small (20 to 25cm) coil and use manual set up for delay, usually around 20, and spider kind of, because it is easy for me to set it up.
Here are some pics of 25cm coil I just made and as You can notice wires are not soldered yet so a)300 b)688 c)784 will come in place after soldering and
making all rigid.

[cvele]

and:

[smit22]

[marin2]

Hello everybody
I always have low values
A: Almost B : 30 nearly C : 40 almost 100

[lc516]

Hello everybody
I always have low values
A: Almost B : 30 nearly C : 40 almost 100

You can show your coil

[karim1980]

ici 357 is not original

[marin2]

Here the coil 27 round diameter 28 cm
Wire diameter 0.7 mm
And voila 357 is it original ????

[cvele]

Hi marin2
inductance of Your coil is too high 591uH, Try with 25 turns and if not good enough, go to 24, lf357 looks ok but do not use holders for transistor, just solder it directly on PCB.
A little bit more about coil - try some other tips (basket or spider), there are a lot of examples on geo.
regard

[marin2]

thank you very much cvele
How do you calculate coil?
I have decreased to 24 turns
But it's always better 37 37 45
Detection coin of diameter 3 cm to 14 cm

[cvele]

to marin2
there are a lot of coil calculators online, just go to google and try (coil calculator), I am a little bit confused with Your debug numbers.
What are they exactly? a=? b=? c=? (300, 700, 800 - optimum)

[marin2]

to Cvele
debug numbers
A 32 B 35 C 39

[cvele]

No, it cannot be!
May be 320 350 390. In that case lf357 is fake.

[marin2]

With lm318 i always had
500 840 840