IGSL

[ivconic]

I won't loose any phase information.
The TX/RX is frequency locked (totally synchronized) to the clock source (comes from netbook/tablet software). I even do not need to sample the Tx signal.

So who is willing to enter the real DSP world?
Aziz

I am!!!
But i am illiterate in those matters...
Hopefully we have here much more literate people to teach us. If not teach us - than to show us their fully working examples.
Some video clip where such diy DSP is shining... or something similar!
Someting repeatable in own arrangement.
Something! At least something but not only bedlam of words...

[Aziz]

*LOL* (Regarding the debate)

Please Davor, keep on kicking to the "trial & error" - "engineers".

I love your spice simulations and your fresh way of thinking.
Keep up the good work.

Cheers,
Aziz

[ivconic]

*LOL* (Regarding the debate)

Please Davor, keep on kicking to the "trial & error" - "engineers".

I love your spice simulations and your fresh way of thinking.
Keep up the good work.

Cheers,
Aziz

Kicks are accepted. Be prepared on kickbacks!

[Qiaozhi]

Now...this i will say generally, for everybody to read and understand.

Homebrew (or diy) metal detector is worth of positive analyze and positive critics (or negative) only when:

* it is made by yourself,
* experimented with it in workshop,
* tested, checked, "tortured" on many ways,
* taken outdoor on as much as possible different soils,
* tested outdoor in real conditions, with real existing targets in soil,
* aproved by least dozen days spent on real soil and under real life conditions

Otherwise, sitting in front of pc and playing with various spice simulators, reading and misusing various Wikipedia articles (),
playing "smart", using discrete tech terms, calculations, formulas and not having a minute of practical experiences .....
well, all this will make of you only "part-time forum expert" and nothing else.

I totally agree with Ivconic on these points.

Many many state-of-the-art "world beating" circuits have been designed in SPICE simulators, only to fall flat on their faces when tested in the real world. But don't get me wrong, as I'm a huge fan and user of SPICE. However, it has to used in the correct way. By all means, start with your new design idea in SPICE - but then go away and build it. After that, incorporate any real world anomalies (or things you weren't expecting) back into the simulation so that they both agree with each other. You can learn a lot from this methodology.

The Tesoro designs have been around for a number of years and are very successful. If you examine some of the older designs from Fisher, Whites and others, you will see a similar topology. These are all variations on the same theme, and they all work well in the field. The Tesoro approach is not "broken" in any way. Although, of course, improvements can always be made.

[Davor]

Thanks, I'm learning.
Anyway, simonbaker made me think more about this antichatter deal, and I obviously got it wrong in several parts. Fortunately not everywhere.

...That R58 2k2 resistor looks more like it may be part of a Schmitt trigger circuit to me

Actually it has the very same function as a 100k in TGSL/IGSL. Everything else you said is very true.

Delay in current IGSL is dominated by a capacitor in LM358 feedback for all threshold trimmer values except for 0ohm (binary response), while 1M - 22n near comparators does not do much - at any signal level. Considering you really wish to employ a chatter filter, and you are happy with current delays, a feedback capacitor (100n) may require some tinkering. Lower values give more consistent behaviour.

Let me show you (comparator switches at the sudden rise of a green curve)...

[ivconic]

Along with not so good solved comparator hysteresis issue there, last 358 is next weakest part in that stage.
I do agree with your special attention on it.
Also i was very interested in one of your previous observation; where you supposed that 358 can be nicely substituted with a plain comparator.
I think that can make nice difference.
But will need more labour arround it. We don't want only digital behavior there.
Since you are skilled with spice; i suggest you to try that option.
Back to comparator again. It is tendable to self-oscillating in certain moments, not always.
Only in moments where previus stages are not providing enough signal at it's inputs. Inputs than can "flow" for a short moment.
My first move, at the time, was to remove amplitude stabilisation at TX.
Turned to be not so brilliant idea, but i left it as it is because it gave me more spare space on pcb!
Later i tried to boost up more signal to "satisfy" comparators inputs and prevent them to run into self oscillations.
That's why i experimented so wildly with various opamps and amplifications.
Finally that was important reason why i involved second IGSL version with modified TX and Minelab Musketeer coil (stronger and constantly stable signal all the way).
Hysteresis, i tried to correct it, but at the end it turned that original one is most optimized one too (guys from Tesoro do know their job very well).
So... dead end!
From front end up to last 358 is all inter-dependable!

[simonbaker]

"..no sanity..." !?

Thanks SB!

All those years here... and i haven't seen NONE of your work so far!?? Zero!
But i see tons of words instead...

So true...

[simonbaker]

Thanks, I'm learning.
Actually it has the very same function as a 100k in TGSL/IGSL. ...

Because of the positive feedback, it looks like it has some kind of delayed latch function also... but I can't say without simming and/or building the circuit and seeing whole circuit.

-SB

[simonbaker]

"..no sanity..." !?

Thanks SB!

Hi ivconic - if you thought that was about you, I'm sorry... I meant manufacturers' engineers may copy and combine each other's designs without studying each part to be sure it is necessary and best arrangement. So that means maybe room for us to simplify, modify, improve, etc.

Regards,

-SB

[simonbaker]

Thanks, I'm learning.
Anyway, simonbaker made me think more about this antichatter deal, and I obviously got it wrong in several parts. Fortunately not everywhere.
Actually it has the very same function as a 100k in TGSL/IGSL. Everything else you said is very true.

Delay in current IGSL is dominated by a capacitor in LM358 feedback for all threshold trimmer values except for 0ohm (binary response), while 1M - 22n near comparators does not do much - at any signal level. Considering you really wish to employ a chatter filter, and you are happy with current delays, a feedback capacitor (100n) may require some tinkering. Lower values give more consistent behaviour.

Let me show you (comparator switches at the sudden rise of a green curve)...

Hi Davor:

Would you post the LTSpice file for this latest sim?

-SB

[satdaveuk]

I got a ITGSL board just never got round to constructing it, maybe its a good thing if theres improvments to be had.

Regards

[ivconic]

Hi ivconic - if you thought that was about you, I'm sorry... I meant manufacturers' engineers may copy and combine each other's designs without studying each part to be sure it is necessary and best arrangement. So that means maybe room for us to simplify, modify, improve, etc.

Regards,

-SB

I had such impression.
Never mind.
About other things you mentioned: yes it can be the case with some manufacturers, i can not deny nor prove that.
But when it comes to Tesoro (here we dealing with their design) you can't absolutely be right on that!
Tesoro is having their own cognizable "signature" in all of their designs.
Simplicity - yet splendid efficiency and accuracy, especially when we talk about Disc/Geb solution at their designs.
I respect Tesoro that much that i didn't have reason nor need to mess much in their philosophy and try to look smarter than i am.
So i was indeed confused reading your lines...
But hey; never mind!
I don't take things that bad and on longer terms.
Cheers!

[simonbaker]

But when it comes to Tesoro (here we dealing with their design) you can't absolutely be right on that!
Tesoro is having their own cognizable "signature" in all of their designs.

Yes, you know better about that than I would.

!

-SB

[Davor]

Hi Davor:

Would you post the LTSpice file for this latest sim?

-SB

It is very same as the first untouched one, with only difference of stepped GEB channel signal (to show the difference). Here you are...
Once you are playing with it try increasing the threshold pot Rtot.

[simonbaker]

It is very same as the first untouched one, with only difference of stepped GEB channel signal (to show the difference). Here you are...
Once you are playing with it try increasing the threshold pot Rtot.

Yes, I agree with your conclusion that the feedback RC dominates, and looks like we could dump those other caps and 1 meg resistor, which is a useful find, thanks! I'm not experienced enough to know if those parts were intended to help with some real-world glitch of some kind...

-SB