Sandbanks

[surfdetector]

modified from PI Polones

https://www.youtube.com/watch?v=kbILR1xS_kg

inside
[ATTACH]38337[/ATTACH]

modified driver mosfet and sample delay, sample window

spec :
Freq : 200Hz
Pulse Width : 125uS
Sample Delay : 25uS
Sample Window : 50uS
Coil : 302uH


testing :
[ATTACH]38338[/ATTACH]

result:
[ATTACH]38339[/ATTACH]

Hello Wahyu,
I would like to see a picture of the output of your pre-amp if you could post one. Thanks.

[bernte_one]

@ Mr Jaick
can you please upload you board design layout, i would try it too, it seems to have more space for components

@surfdetector
no, and dont add delay option
i achive very good performance with a chinese copy of lf357
and a little optimised damping values
very easy to get good detection with 38cm coil und a smal belt buckle made of bronze (40cm in air) with smooth sound and less chattering


but i think about the pulsewidth mod, so i could go for boost mode while militaria hunting in german oderland

[Andi68]

The Pi Polones is very similar to the Sandbanks.
And without that transformer.

[Andi68]

the 6Volt versionimpulsowy_wykrywacz_metali__1_.pdf

[surfdetector]

@surfdetector
no, and dont add delay option
i achive very good performance with a chinese copy of lf357
and a little optimised damping values
very easy to get good detection with 38cm coil und a smal belt buckle made of bronze (40cm in air) with smooth sound and less chattering


but i think about the pulsewidth mod, so i could go for boost mode while militaria hunting in german oderland

I have added a trimmer on the PCB for the TX pulse width.
My LF357 seems to stay in saturation for a long time, I would like to see a scope shot of another LF357 pin #6

[bernte_one]

i would take a minimal value (fixed resistor) in series with a variable resistor

i can make a scope shot but only indoor

[Mr.Jaick]

How did you choose the size of your damping resistor? Did you use the variable damping tool? I am thinking that it is not sized optimally.
Cheers

I was trying to use a damping tool, but i think i made it the wrong way, anyway
since then i've been changing everything to get the optimal performance but not yet
new information:
coil 19 turns flat wind 0.5mm enameled with 2.5ohms DC resistance
damping resistor 560 (is better for that coil)
battery is 16v
it detects a big 32cm steel tray at max about 110cm with a 50cm coil
a big alloy coin at 20 or there about depends on the preAmp IC
i tried many different ICs for pre amp but all of my LF357 chips are chattering and i can't adjust my threshold well
i ordered a polones kit to compare it and see what's wrong, my board or components?

[surfdetector]

i would take a minimal value (fixed resistor) in series with a variable resistor

Yes yours is the better way with the series resistor.

i can make a scope shot but only indoor

A scope shot of the LF357 output would be great, no problem that it is indoors for me.

Thanks

[Mr.Jaick]

[QUOTE=bernte_one;281395]@ Mr Jaick
can you please upload you board design layout, i would try it too, it seems to have more space for components

I've been changing and modifying the pcb
now it's a bit messy but you can fix it and change it however you want:
Polones.zipi tried to find the old autosave ones but i couldn't sorry

[6666]

[QUOTE=Mr.Jaick;281408]

@ Mr Jaick
can you please upload you board design layout, i would try it too, it seems to have more space for components

I've been changing and modifying the pcb
now it's a bit messy but you can fix it and change it however you want:
[ATTACH=CONFIG]53418[/ATTACH]i tried to find the old autosave ones but i couldn't sorry

What program opens the pcb file in the zip file ?

[kt315]

[QUOTE=6666;281415]

What program opens the pcb file in the zip file ?

WINRAR. https://rutracker.org/forum/viewtopic.php?t=5918606


Zockoyka
Стаж: 2 года 3 месяца
working like a charm, thank you so much

[6666]

Thanks KT, but I am asking what program is the pcb file for. not what opens the zip file.

[surfdetector]

Thanks KT, but I am asking what program is the pcb file for. not what opens the zip file.

Altium Designer

[6666]

Altium Designer

Thanks I did not recognise the suffix, are you paying US$320 per month to use it

[kt315]

Thanks I did not recognise the suffix, are you paying US$320 per month to use it

For now I'll try to build up the Surf PI design because I can do that without spending any money.

O_0