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

[ppodg]

ivconic,
two different subjects
1. decoupling - lm318 loves to oscillate
2. aliasing - your scope's sampling frequency seems too low at slow tb (time base). Try faster tb or a crt (analog) scope.
3. my Engish isn't perfect either

[ivconic]

ivconic,
two different subjects
1. decoupling - lm318 loves to oscillate
2. aliasing - your scope's sampling frequency seems too low at slow tb (time base). Try faster tb or a crt (analog) scope.
3. my Engish isn't perfect either

1. clear now.
2. true. don't have one.will look for it.
3. Consolation is in fact that my English is better than my Chinese!

[ivconic]

ivconic,
two different subjects
1. decoupling - lm318 loves to oscillate
2. aliasing - your scope's sampling frequency seems too low at slow tb (time base). Try faster tb or a crt (analog) scope.
3. my Engish isn't perfect either

"...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:





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

[Davor]

TB also stands for tuberculosis, and it is not funny.

The star discrete component for the fast low noise is BF863 JFET. It may easily be matched.

[TreasureHunter]

hello everyone!

I dont have ATMEGA, just an UNO as microcontroller. My question is, can this be simplified to be compatible with UNO if we remove the LCD panel?

[ODM]

...
[ATTACH]35427[/ATTACH]

What does adding extra compensation capacitors do for overdrive recovery, does the datasheet have any text specifically about that? Unless otherwise stated it's safe to at least expect any/all compensation capacitors can fudge with biasing when an opamp is overdriven.

Simulators will 99% of the time not model that kind of overload recovery, so it's (un)fortunately time to bench test it with a scope.

[green]

Was going to add the 1N4148 data to the chart I did the other day, Forgot so here it is. Added Coke can chart to reply. The diode has a lot longer time constant than the can targets, actually longer than a whole can.

[ppodg]

@green
kovar wires

[ivconic]

hello everyone!

I dont have ATMEGA, just an UNO as microcontroller. My question is, can this be simplified to be compatible with UNO if we remove the LCD panel?

You missed to see this:

First i made it with UNO, just to test the code. As coil i used micro coil from floppy drive.
And you don't need to remove LCD.
Why would you remove it?
How you will see what 's going on?

Here it is in action:

[ivconic]

What does adding extra compensation capacitors do for overdrive recovery, does the datasheet have any text specifically about that? Unless otherwise stated it's safe to at least expect any/all compensation capacitors can fudge with biasing when an opamp is overdriven.

Simulators will 99% of the time not model that kind of overload recovery, so it's (un)fortunately time to bench test it with a scope.

...

[ivconic]

Was going to add the 1N4148 data to the chart I did the other day, Forgot so here it is. Added Coke can chart to reply. The diode has a lot longer time constant than the can targets, actually longer than a whole can.

Very good job!
We will accept those as references.
Cola can cut in pieces as you suggested would be universal reference.

[Speedy_G]

Was going to add the 1N4148 data to the chart I did the other day, Forgot so here it is. Added Coke can chart to reply. The diode has a lot longer time constant than the can targets, actually longer than a whole can.

Hi Green

I'm very interested how you obtained TC = 44 us for the 1N4148 from your graph. I read it as closer to TC = 26 us (perhaps 28 us -with linear regression). I'm a little ignorant when it comes to reading such graphical representations. :-(
Also what is that time constant for a whole aluminium Coke can?

Thanks,

Ciao

Speedy_G

[green]

Hi Green

I'm very interested how you obtained TC = 44 us for the 1N4148 from your graph. I read it as closer to TC = 26 us (perhaps 28 us -with linear regression). I'm a little ignorant when it comes to reading such graphical representations. :-(
Also what is that time constant for a whole aluminium Coke can?

Thanks,

Ciao

Speedy_G

Longer time constant targets don't decay exponential for the whole decay so it depends where you draw the line. I usually draw the line parallel to the trace where it is exponential, then take the difference in time where the line crosses with a 20 to 1 ratio, 2/.1 as an example(3 time constants) and divide by three. Another way for 1 time constant is the time difference where the line crosses 8 and then 3. Maybe I'm doing it wrong. I looked up the can data and it was close to the diode, I had remembered the can to be a little faster. The Tx waveform and time effects the earlier part of the decay so I haven't drawn the line there.

[ivconic]

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



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

[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!

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.