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

[Old cart]

Since it actually is real dsp it may be liable to aliasing if analogue part is not filtered well. (Actually we can only talk on analogue part until we get source somehow.)
You said "decoupling" and i would like to hear more detailed explanation.
Explain "tb"...excuse me for my English!

Decoupling are the caps you place on the power supply lines to ground to lower the impedance of the supply at high frequencies.

[Old cart]

"...your scope's sampling frequency seems too low at slow tb (time base). Try faster tb ..."

Arghhh!
Now i understand!
Like i said; i am still adapting on this scope...
Even when i was recording those videos; i couldn't find how to adjust time base!
That's why i changed sampling frequency few times to try to "catch" the waveform! (flip!flip!)
And now when you noticed that; i downloaded manual for it... and it was already there right in front of my eyes all the time!!!
CRT scope with hypnotic flicking display and lot of dedicated knobs... good old times!!!
Here it is:
[ATTACH]35430[/ATTACH]




Even on 24" led monitor i still need the magnifying glass to locate the magnifying glass icons!!!
Oh what a shame!!!

Ivconic, this scope shot still has some aliasing due to a sample rate not high enough. The more notable type of aliasing is called perceptual aliasing or visual aliasing. It is not real aliasing per se but is caused by the human eye and brain trying to connect points and the display resolution of you monitor "beating" with one another. The effect is similar to what you would see if you have two pieces of transparent plastic with closely placed lines on them and placing them on top of one another. When you slide them over each other you will see the effect.

[ODM]

...

Apparently not, the text itself only refers to a way to milk out high slew rate from the opamp, and then follows up with another (different) circuit that solves ringing problems.

The suggested external connection is 2kohm/10nF with a time constant of 20us, while the internal capacitors are in the order of picofarads. Overloading that external connection could cause a potential recovery time of 80-100us. I'd be very wary of adding it without a scope to check it, particularly if the detector relies on software for sensitivity and the software is a "black box".

[ivconic]

Ivconic, he means your scope is aliasing because the time base is set too slow try a faster sweep speed. I noticed that scope can only sample 2.5 Ms/ s ( one sample every 400nS) so you will have to run it near the limits. If the trigger is good the waveform will stabilize and lock when you are no longer aliasing.

I realized what he was talking about just minute after i posted that post!
I couldn't find a way to adjust time base at that moment when i recorded videos, because time base adjustments are not present in main adjustments menu.
Time base can be adjusted only with "magnifying glass +/-" symbols on the main screen, and those are small and somehow i didn't noticed them at that moment.
Holding camera in one hand and probe in another; i was focused mostly on not to touch wrong voltage with a probe.
Later i got the impression that he is talking about "aliasing" look alike error at adc of Atmega... Funny confusion!
And i changed sampling frequency few times, trying to catch waveform enough visible to distinguish if it is "complex" (as claimed it is similar to ML) or is it "dull" simple TX.
Although it makes not much sense; actually it was possible to catch the waveform by changing sampling frequency... though it was not stable as all of you already noticed.
Aliasing in that particular case is not of huge importance, not an obstacle, because i only wanted to see if waveform is simple or complex.
And decoupling i know what it is, but i thought he has something more special on his mind.
Anyway, all the confusions are now cleared up. Thanks for helping me understand!

[Qiaozhi]

Somebody should stop me; i don't know what am i doing!!!



Anybody familiar with Multisim??
This is my first attempt...

[ATTACH]35440[/ATTACH]

You need to add the 390R resistor between XFG1 and R7.
Also, I'm not familiar with the peculiarities of Multisim, but should R1 be marked as 1M? In SPICE format, a value of 1M (or even 1m) indicates a 1 milli-ohm resistor. You need to use 1MEG (or 1meg) for mega-ohm. Perhaps the Multisim schematic is case sensitive, and 1M gets converted when the SPICE netlist is generated? Have a look at the netlist to check.

[TreasureHunter]

Hello ivconic!

That is perfect!! I wanted to remove LCD because I thought that an UNO does not have enough IO pins like MEGA does. And I will use a mobile application through bluetooth connection for display, so I don't need LCD. Can I have a schematics please for the UNO version? Is it running the same program as well as the MEGA version?

Thanks in advance!

TH

[Old cart]

I realized what he was talking about just minute after i posted that post!
I couldn't find a way to adjust time base at that moment when i recorded videos, because time base adjustments are not present in main adjustments menu.
Time base can be adjusted only with "magnifying glass +/-" symbols on the main screen, and those are small and somehow i didn't noticed them at that moment.
Holding camera in one hand and probe in another; i was focused mostly on not to touch wrong voltage with a probe.
Later i got the impression that he is talking about "aliasing" look alike error at adc of Atmega... Funny confusion!
And i changed sampling frequency few times, trying to catch waveform enough visible to distinguish if it is "complex" (as claimed it is similar to ML) or is it "dull" simple TX.
Although it makes not much sense; actually it was possible to catch the waveform by changing sampling frequency... though it was not stable as all of you already noticed.
Aliasing in that particular case is not of huge importance, not an obstacle, because i only wanted to see if waveform is simple or complex.
And decoupling i know what it is, but i thought he has something more special on his mind.r looked triggered to me.
Anyway, all the confusions are now cleared up. Thanks for helping me understand!

Ivconic, sorry I did note that after I wrote the explainations. Still it never looked triggered to me. If changing the sample rate gives the appearance of stability but the waveform is still drifting you need to be cautious with any conclusions you make about the waveform. It can be totally wrong. This means you still have to few samples to adequately allow the digital scope to reconstruct the waveform. It is best on a digital scope to increase the sweep speed and after each increase observe that the waveform is getting more zoomed in. If it does not and gets more compressed this is a sure sign that you are aliased and that the waveform is false.

[ivconic]

Hello ivconic!

That is perfect!! I wanted to remove LCD because I thought that an UNO does not have enough IO pins like MEGA does. And I will use a mobile application through bluetooth connection for display, so I don't need LCD. Can I have a schematics please for the UNO version? Is it running the same program as well as the MEGA version?

Thanks in advance!

TH

List this topic from the first pages, you will find my schematics, adaptations of schematic done by Qiaozhi.
Actually you don't need many I/O's .
Or give me your email and i will send you schematics... few of those, adaptations for UNO and MINI Pro.
Code is the same.

[ivconic]

Ivconic, sorry I did note that after I wrote the explainations. Still it never looked triggered to me. If changing the sample rate gives the appearance of stability but the waveform is still drifting you need to be cautious with any conclusions you make about the waveform. It can be totally wrong. This means you still have to few samples to adequately allow the digital scope to reconstruct the waveform. It is best on a digital scope to increase the sweep speed and after each increase observe that the waveform is getting more zoomed in. If it does not and gets more compressed this is a sure sign that you are aliased and that the waveform is false.

Absolutely correct and agree.
Just because of that; today i made another one!
But this one is on my version of pcb which is bit more "comfortable" for scope probing.
Previous one is already well packed in enclosure and it was delicate to open it again and "poke" it with probes here and there.
To avoid that in future measurements i made another one which i will not pack, it will stay the ways it is.
Now is ready for "scoping" all the way!
Here are videos that i did a minute ago, just finished it. Coil is again small coil from old 5.25" floppy drive. Just for testing purposes.

[ivconic]

And in action:

[ivconic]

You need to add the 390R resistor between XFG1 and R7.
Also, I'm not familiar with the peculiarities of Multisim, but should R1 be marked as 1M? In SPICE format, a value of 1M (or even 1m) indicates a 1 milli-ohm resistor. You need to use 1MEG (or 1meg) for mega-ohm. Perhaps the Multisim schematic is case sensitive, and 1M gets converted when the SPICE netlist is generated? Have a look at the netlist to check.

Yes 390R is missing.
The other one is indeed 1Mohms. I checked in the list, it's the proper one.

[TreasureHunter]

List this topic from the first pages, you will find my schematics, adaptations of schematic done by Qiaozhi.
Actually you don't need many I/O's .
Or give me your email and i will send you schematics... few of those, adaptations for UNO and MINI Pro.
Code is the same.

Okay, I wrote you a private message with my email address.

[pigeon]

Absolutely correct and agree.
Just because of that; today i made another one!
But this one is on my version of pcb which is bit more "comfortable" for scope probing.
Previous one is already well packed in enclosure and it was delicate to open it again and "poke" it with probes here and there.
To avoid that in future measurements i made another one which i will not pack, it will stay the ways it is.
Now is ready for "scoping" all the way!
Here are videos that i did a minute ago, just finished it. Coil is again small coil from old 5.25" floppy drive. Just for testing purposes.

HI IVONIC

is that it is possible to give me your own pcb?

thank you

[ivconic]

...

[karim1980]

...

elegant pcb
thank you ivconic