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

[Geo]

ML Commander 11" mono coil
A=253 B=626 C=764
Sens=15 delay=19 (13+6) Speed=10 GB=5
It detects a 1Euro coin at 26cm and a soda can at 55cm with continued sound.

[Geo]

Whites TDI 12" Dual Field
A=345 B=691 C=786
Sens=15 delay=19 (14+6) Speed=10 GB=5
It detects a 1Euro coin at 25cm and a soda can at 55cm with continued sound.

[Geo]

Home made Basket 40cm coil (15.5")
A=277 B=578 C=720
Sens=15 delay=17 (11+6) Speed=10 GB=5
It detects a 1Euro coin at 28cm and a soda can at 67cm with continued sound.

[Geo]

It makes sense, TDI coil is concentric coplanar right?
It's RX coil is smaller than at other two coils?
Also i guess it is most precise in behavior, among all three coils, right?

I did not check about discrimination or ferrous reject.
Maybe later...
I think that Commander and DIY coils needs a series resistor because they have smaller resistor than 1_Ohn that Hamid gives. Also if we see at waveforms we see that at these two coils there is something as small oscillation maybe from higher current.

[Geo]

Also i tried 2 ICs LTE49990 at place of LF357 but did n't work at all. Any idea why??????

[basellafe]

Try lf356

[green]

Also i tried 2 ICs LTE49990 at place of LF357 but did n't work at all. Any idea why??????

I was thinking bias current but maybe not. Have you compared amplifier out with the LF357 and the LME49990. Including a LT spice simulation of what I think amplifier out might look like with no target and an aluminum soda can.

[Altair]

Also i tried 2 ICs LTE49990 at place of LF357 but did n't work at all. Any idea why??????

May be LME49990 instead of LTE49990??
If yes, consider that LME49990 has 22V/uS slew rate against 50V/uS of LF357...

[6666]

I was thinking bias current but maybe not. Have you compared amplifier out with the LF357 and the LME49990. Including a LT spice simulation of what I think amplifier out might look like with no target and an aluminum soda can.

Hi Green would you mind posting your spice file thanks,
would be handy .

[Geo]

May be LME49990 instead of LTE49990??
If yes, consider that LME49990 has 22V/uS slew rate against 50V/uS of LF357...

Yes its LME49990 (my mistake) but why don't work at all?? At afternoom i tried another one with the same bad results...

[Geo]

I was thinking bias current but maybe not. Have you compared amplifier out with the LF357 and the LME49990. Including a LT spice simulation of what I think amplifier out might look like with no target and an aluminum soda can.

No I did n't compare amplifier... and i have mistake ,the problematic ic is the LME49990 ,not the LTE....

[Geo]

Try lf356

LF356.....why????
I use LF357 with 20Mhz bandwidth but i am looking for something better, not for worst.

[Altair]

I would try with LT1363; I've played a bit with front end simulation and seems me promise but I haven't tried it with hardware yet.

[green]

Hi Green would you mind posting your spice file thanks,
would be handy .

No target simulation. Change R11 to vary target time constant. L/R, 4uH/.1 ohm=40usecTC about the same as an aluminum soda can. Change L1(C par)to see coil resonance effect. Change R5 to damp coil with different C par. Playing with C par in spice, I'm guessing coil capacitance is a big reason coils act different. Adjusting R damping(R5) should solve the problem.

[green]

No I did n't compare amplifier... and i have mistake ,the problematic ic is the LME49990 ,not the LTE....

Do you have a scope? I would be interested in seeing amplifier out, similar to reply 1207 with the two different amplifiers(LF357 and LME49990). It might be easier to answer your question with the scope pictures.