IGSL

[ivconic]

Metal detector terminology we got used on here somewhat differs from what you might expect to be called as "notch", "treshold", "sense" etc...
I noticed earlier that you are having bit different understanding of those terms.
Not a problem at all, as long as we speak about same function in circuitry.
I told you before that second GEB channels is not there for no reason; now you can adapt it for what you need, relating to salt water.
Was not my initial idea (logically; i don't have salt water problems here) but now it turns usable in other perspectives too.
...
If you want to examine more possibilities than that; i would like to point you on Pantera circuitry as well.
Recently i made it and it behaves pretty interesting, way over my expectations.
Pantera's Notch is something i would like to point you on.
(William Lahr again made no mistakes, schematic is 100% accurate. Thumbs up for him!)
Cheers!

[Davor]

I've analysed a King Cobra schematic in great detail, and the thing they call "Notch" there is actually a range of exclusion angles, not a notch. So it is like saying "notch" for a band reject filter. The terminology mess is most probably a result of a term "reject" being already used for discrimination.

Besides, such level of control is already present in IGSL by means of independent discrimination setups.

What I have in mind is a real sharp (amplitude independent) and narrow rejection angle that is set exactly as GEB for the ferrites, but notching out only a narrow angle around the wet salts. That would enable me to set discriminations as usual, but also enjoy the absence of reaction to wet salts. I really want this to be very sharp because small gold is very close to wet salts.

So in short, we are not speaking of the same feature here.

[Qiaozhi]

Don't be impatient

For some idea to materialise you need some basic mechanisms that may play in your head. A kind of pseudocode. When you are done playing, and it passed all scrutiny, then it becomes a hardware coding candidate.

This wet salt notch for example... at first I thought of implementing it with comparators, and to turn one of the comparators into an inverting opamp to do everything right ... wrong - they oscillate. So The next best thing is an absolute value circuit followed by a comparator with Disc Sens as a reference, and all made with LM324 because of low offset and power consumption. We'll see. Soon.

It is still boiling. When it is cooked I'll make it a schematic, and a wiring plan to incorporate into the existing IGSL.

The idea is (almost) simple: make a separate ground balance for wet salts that will enable IGSL work well on beaches.

I'll have to invent a synthetic test for it's operation as I'll not be near the seaside till spring.

Have a look at the Golden Sabre schematic. It already has a notch feature.

[Davor]

Don't be impatient

For some idea to materialise you need some basic mechanisms that may play in your head. A kind of pseudocode. When you are done playing, and it passed all scrutiny, then it becomes a hardware coding candidate.

This wet salt notch for example... at first I thought of implementing it with comparators, and to turn one of the comparators into an inverting opamp to do everything right ... wrong - they oscillate. So The next best thing is an absolute value circuit followed by a comparator with Disc Sens as a reference, and all made with LM324 because of low offset and power consumption. We'll see. Soon.

It is still boiling. When it is cooked I'll make it a schematic, and a wiring plan to incorporate into the existing IGSL.

The idea is (almost) simple: make a separate ground balance for wet salts that will enable IGSL work well on beaches.

I'll have to invent a synthetic test for it's operation as I'll not be near the seaside till spring.

[ivconic]

Davor it is tough to follow your ideas without schematics.
And less interesting too.
Can't you master some simple schematic capture software and start drawing your ideas?
ExpressSCH (part of ExpressPCB package) is ultra-simple yet very potent software for such task.
And it is free for downloading and using.
With your level of intelligence you will master it in 2 minutes.
Than your ideas will be "materialized" and more interesting for others to follow here.
Regards!

[Davor]

A new mod is on the way...

I am musing with the idea of notching out the wet salt vector in my IGSL so that it becomes more useful at beaches, and so far I had some elaborate ideas of how to do it in a complicated way. The catch is that there is a simple solution lurking from my previous mods already.

A key feature is a redundant GEB channel that will learn some new tricks.

A GEB channel already has a notch at ferrites - that's one of it's functions. The other function is providing a target proportional signal for the further tone circuitry. The only thing missing is a null at times when Disc channel that is aligned with wet salts passes zero crossing.

Unlike GEB that is positive for all metals, a Disc channel has different polarity for Fe vs Cu, so I need a window comparator that will go low while Disc signal is lower than Disc sens voltage in positive and negative direction. It will be used to collapse a GEB output (tone volume). And that's it.

In total there will be 3 Disc channels in a finished mod: Cu, Fe, and wet salt. While Cu and Fe will be freely adjustable as we are used to, a wet salt will have to be carefully adjusted just as GEB channel, so that it precisely notches out only the salts.

It is only a single comparator chip and a multiturn trimmer away.

[Qiaozhi]

These define the high pass filter cut-off frequency. With halved capacitances you'll have to swing your coil twice as fast

IMHO it is a bad idea to go for lower capacitances because it shortens the target response time.

The correct type used by Tesoro is bipolar 4.7uF electrolytic.
Ivconic used 2 standard 10uF electrolytics back-to-back and in series (to give 5uF) because he did not have bipolar caps available.

[Davor]

These define the high pass filter cut-off frequency. With halved capacitances you'll have to swing your coil twice as fast

IMHO it is a bad idea to go for lower capacitances because it shortens the target response time. I am considering to at least double the capacitances in my rig. Going for a lower cutt-off leads to more noise (1/f noise that is), but also to more non-motion like response. Most probably I'll have to replace the gain blocks op amps with some less noisy specimens, or at least with a lower 1/f knee. Otherwise going for much lower cutt-off would lead to much more chattering.

It could be the next mod. Only I have to find a proper op amp with noise less than 50nV/sqrt(Hz) at 10Hz. So far LF347 and TL074 are just about there, but I'd better find some better chips that use less power and cost not too much.

[ivconic]

hello
acoording to the partlist form silverdog
i made three igsl
with
C15a,C15b,C25a,C25b,C28a,C28b,C38a,C38b 4.7uF

but shematic say 10uF to get 4,7uF bipol i have never compared that because all machines work good

which task have the bipol elkos and can i achieve better resulsts with 10uf instead

regards

Ehhm... actually it is better to use bipolar than ordinary elcos.
But bipolar caps are harder to find, when needed, here in local shops, that's why i always "reserve" place on my pcb's for two ordinary elcos to replace one bipolar.
Usually it is only temporary solution; just to check functionality of the rest of circuit, than later i do replace ordinary ones with bipolar.
So you better use bipolar if you can easily obtain those.
Cheers!

[bernte_one]

hello
acoording to the partlist form silverdog
i made three igsl
with
C15a,C15b,C25a,C25b,C28a,C28b,C38a,C38b 4.7uF

but shematic say 10uF to get 4,7uF bipol i have never compared that because all machines work good

which task have the bipol elkos and can i achieve better resulsts with 10uf instead

regards

[der_fisherman]

It is definitely a "winter" job as you say!!!

[ivconic]

hello fisherman

i think ivica has many luck to live there where he live the deepest temperature is in january i have read in middle -1,5dg celsius
while we have to fight with frozen ground and down to -25degree celsius

i suppose so fast he dont return into his workshop

at moment we have -2 till +5 celsius here so my workshop season starts already

but i have heared people tell that a stron winter is coming to serbia too


regards and nice weekend

Oh i am not that lucky!
We have here long and cold winters too.
January is toughest, usually goes under -15 and last for 20 days and more.

Ok, Berlin is on North and you have there even toughest winter, i know.

I think i will have nice days for hobby only until December 20.-25. Later i will "enjoy" same winter as you do there on North.
Than... until end of March...workshop!

[ivconic]

Dear Davor & Ivconic,
I see that Bernte_one is as interested as myself in getting our IGSLs up to the latest version.....
Please believe me that I don't want to put any pressure on anyone, especially if it is felt to be too soon, I am willing to wait longer. (Assuming for the moment that you, Davor, are willing to do something along those lines).
I would also be pleased, if the changes were to be also "run by" Ivconic, assuming that he is willing to do that, as I am personally a great believer in "two heads are better than one!".
I don't know if my thoughts on this are either correct, valid or even possible, but from my point of view, we appear to have two really great brains here and the end result must be better when these two have some sort of agreement as to what is a good idea and how to implement it......
I have placed my IGSL in the loft to await (hopefully) such changes and additions before spring 2013.
Best wishes to all concerned.

No problem at all. Of course i am willing to apply Davor's mods. Looking forward.
But right now i am under "coinshooting rush" until first snow to come!
Want to take advance of last sunny days in this year.
So i planned to delay such works for the winter when it is not possible to go outdoor and enjoy searching.
Pity; it will be short period, pretty soon we will have cold winter here.
So we will talk about works on IGSL very soon.
Cheers!

[ivconic]

hello ivica

which version of deus you use
does it work ok without remote control with headphone control only
or do you think the remote control is a must for this unit?

@davor
can you make a summary of your igsl mods

regards

I bought full complete; remote, headphones, both coils, stem, charger....
Yes it works quite fine with headphones only. No differences in performances at all.
Remote is needed only when you want to adjust some additional (expert) adjustments and it is good to have it, of course.

But not mandatory. You may start with headphones and much more later buy remote, no problem.

Or you may buy whole complete and split it on two separate independent "detectors" with some friend.
That's even better because you will pay less and have indeed two detectors.
Cheers!

[Davor]

My sims of a igsl tgsl showed that such a condition is quite possible if R2 is not connected (or is much larger than on schematic). Q1 becomes over biassed and a result is a reduced oscillation.