Polish Pi

[surfdetector]

I did it
now it seems to me my delay time is 100uS!
channel X on pin 6 of LF357(TL071 in my case)
channel Y on pin 10 of 4011
the top waveform is LF357 and bottom is 4011
[ATTACH]53440[/ATTACH]
volt/div = 10v time/div = 50uS
i played with trigger and trigger source but couldn't make it smaller
what should i do now? reduce the two 33k resistors?

I am afraid that I cannot see the screen of your oscilloscope well enough to be able to tell what is there.

I should have explained better. Pin 3 of the 4011 will show the delay pulse and pin 10 will show the sample pulse. The two 33k resistors are for the delay pulse and the two 47k resistors are for the Sample pulse. If you have channel 1 on pin 3 of the pre-amp and channel 2 on pin #10 of the 4011 then you will see the Sample pulse in relation to the pre-amp output and will be able to visualize the Sample delay.

[Hammerhead]

I believe he is saying that the TL081 works with a 30cm coil and the LF357 and 356 do not, however they work with smaller coils

Your words are correct, my friend, I am sorry, I speak little English Do you speak Arabic

[Mr.Jaick]

I am afraid that I cannot see the screen of your oscilloscope well enough to be able to tell what is there.

I should have explained better. Pin 3 of the 4011 will show the delay pulse and pin 10 will show the sample pulse. The two 33k resistors are for the delay pulse and the two 47k resistors are for the Sample pulse. If you have channel 1 on pin 3 of the pre-amp and channel 2 on pin #10 of the 4011 then you will see the Sample pulse in relation to the pre-amp output and will be able to visualize the Sample delay.

my oscilloscope intensity is bad
this is what happens


ok this is what i understand from your words:

Pin 3 of the 4011 will show the delay pulse and pin 10 will show the sample pulse.

if I probe the PIN 3 of 4011 on channel one and pin 10 of 4011 on channel two, then measure the time delay between these two pulses
then I got the sampel delay which should be 50us, right?

If you have channel 1 on pin 3 of the pre-amp and channel 2 on pin #10 of the 4011 then you will see the Sample pulse in relation to the pre-amp output and will be able to visualize the Sample delay.

i think you meant to say pin 6 of pre_amp because pin 3 is all DC !
so with that in mind the picture i sent here was the sample delay that should be 50us?! is that right?

[6666]

my oscilloscope intensity is bad
this is what happens

Take your pictures with the lights off, close the blinds make it dark.

[Mr.Jaick]

this is the delay between pin 3 and 10 of 4011

it's 20us difference
my apologies for the crudity of the picture

[surfdetector]

i think you meant to say pin 6 of pre_amp because pin 3 is all DC !
so with that in mind the picture i sent here was the sample delay that should be 50us?! is that right?

Yes I did mean to say pin 6 of the pre-amp. If you take a look at my video below you will see what the pre-amp, the sample delay and the sample pulse width look like on my scope.
https://youtu.be/6O1GtleFi0E?t=106

[Mr.Jaick]

Yes I did mean to say pin 6 of the pre-amp. If you take a look at my video below you will see what the pre-amp, the sample delay and the sample pulse width look like on my scope.
https://youtu.be/6O1GtleFi0E?t=106

hey i watched all of your polones series they are great, you were taking some long pauses but with 1.25X speed that's all good
now what i understand is my delay pulse from 4011 is kinda behind the pin6 of pre_amp signal as you might notice from pictures that i posted
it should be in front like yours, i don't know if it's the scope or the circuit
BTW i changed the 33k resistors to 20k and i feel like the small object detection got better by a few centimeters.
the only problem i have for now is depth
coil: 50cm flat winded 19 turns 0.5mm enameled 2.5ohm with 16v battery
test objects:

coin = 35cm
ring = 20cm
needle nose plier = 45cm
copper pipe = 40cm
steel tray(32cm dimeter) = 130cm

[Bayu]

https://youtu.be/Jn-ncWP65os

Modif frekuency 1200hz + vco

[6666]

https://youtu.be/Jn-ncWP65os

Modif frekuency 1200hz + vco

Good sounding vco, what did you use for the vco ?

[surfdetector]

https://youtu.be/Jn-ncWP65os

Modif frekuency 1200hz + vco

Hello Bayu,
Would you please post a closeup picture of your PCB? Thanks.

[Mr.Jaick]

I think we need a new vco on this device
it just bugs me, too slow and sluggish, background sound is just on my nervous when metal detecting
the device itself is quite good for a simple design but sound interface is terrible...


I tried this one and it works but degrades the detection depth severely
also this one which is an idea from hammerhead but doesn't work on this


i don't have a problem with VCO but without a background sound or at least a high pitch low volume one
and doesn't have to be VCO necessarily but amplitude modulation is really handy

any recommendation please?

[surfdetector]

Good sounding vco, what did you use for the vco ?

@Bayu, what did you use as your schema for the VCO?

[yhl]

I have Polish PI improved circuit, using CD4046

[yhl]

[Mr.Jaick]

does it affect detection depth?
I suppose you've used a LM358 dual op amp as the input and output buffer stage for cd4046 VCO and some transistors for audio drive



I just want to know how do you connect this to the original board?NPN transistor?
will you share the schematic ?