Sandbanks

[6666]

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

[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 ?

[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

[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]

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?

[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

[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

[Andi68]

the 6Volt versionimpulsowy_wykrywacz_metali__1_.pdf

[Andi68]

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

[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

[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.

[surfdetector]

can anybody help on this problem?
i made my own PCB for this polones schematic
[ATTACH]53239[/ATTACH]
[ATTACH]53247[/ATTACH]

layout is ok connections are ok but it hardly detects a big iron lock
coil information:
0.75mm enameled
13 turns
1 ohm
should be about 260uh
damping resistor 470 ohms
gain of PreAmp is 3700 (on the high side)

here are all the necessary information of the running circuit
settings are : volt/div= 5v time/div= 2ms otherwise mentioned
1_oscillator output
[ATTACH]53240[/ATTACH]

2_gate of IRF740
[ATTACH]53241[/ATTACH]

3_Drain of IRF740
volt/div = 20V time/div = 2ms
[ATTACH]53242[/ATTACH]

4_drain of IRF740 zoomed out Back EMF
volt/div = 10v time/div = 20us
[ATTACH]53243[/ATTACH]
it has a bit of undershoot on the falling edge about 0.5V

5_cathode of 3,3V zener in front of PreAmp
[ATTACH]53244[/ATTACH]

6_pin 10 of 4011BP
[ATTACH]53245[/ATTACH]

7_pin 6 of preAmp
[ATTACH]53246[/ATTACH]

any help would be great

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

[surfdetector]

820k under lf357 changed to 1M

Bernte did you put trimmers in place of the two 33k resistors to enable changing the sample delay?

[Mr.Jaick]

200us PULSE WIDTH gives 400V p-p. you can not check pulse on the gate because you DO NOT SEE IT.
so also it is HIGHT VOLTAGE and you will burn your o-scope in moment.

i changed the pulldown resistor(R7) on the gate from 33k to 220 ohms and i think it was too low that the mosfet didn't fully turn on(it was dead cold)
I changed that to 2.2k and it's better i guess
now the PULSE WIDTH is 70us or there about and mosfet doesn't get hot at all
detection is improved just tiny bit and i think the problem must be in coil driver and coil itself

do you know what is the optimum gate pulldown resistor for the IRF740 ??
the series resistor for gate(R6) is 27 ohms

now i'll just add couple of turns to the coil see what happens