IGSL

[liekwang]

?Hi I have davor respectively 6volt and 0volt voltage in rx and tx is it good

[Davor]

To get any sound out of IGSL (and in fact most of Tesoro descents) you need a working Tx oscillator. So if you want you device to start doing something, make sure your Tx coil is connected, and oscillator works, next see that you have -6V, and so on.

[liekwang]

?But it did not work at all and there is no sound coming out of speakers later try I check again because I was tired of my often fail to create metal detector but I made surf really well with his sensitive that I don't like to surf too much false signals

[Davor]

Are you sure you didn't put 7809 by mistake? I'd be surprised to see 9V as output for 7808, but even that will not ruin anything ... provided you have good 12V source. The whole point of using 7808 instead of 7809 is that you have a little more headroom before the low battery problems become too annoying. Otherwise 9V would be just fine.

[liekwang]

?Davor pin out 7808 get 9 volt not 8volt why not 8volt

[Davor]

ICs as per schematic are OK. You can replace U5 and U6 with TL061 for lower consumption, or TL071 for a bit lower noise.
It is preferable to use 4u7 bipolar capacitors as indicated. There are some advantages in using bipolars over using back to back capacitors.
The largest capacitor (1000uF) was drawn opposite on my board, so please make sure to turn it properly if it is the case on your board as well.

It is advisable to make a pin-swap mod to make sure Fe channel works well. You may apply some other mods on the go.

[liekwang]

davor

?Hi can you please tell me what to put in the type of ic U1, U2, U5, U6, U7, U8, U12 I am confused I built a petravka the Board layout in page 22 please let me know

[Davor]

Shattering sound is most probably a consequence of "Disc threshold" trimmers cranked all the way. It turns U8a and u8b into a kind of slow recovering comparator, or worse if you used some opamp other than LM358. Most opamps are very unhappy if + and - inputs depart by more than 0.5V, and that's what happens when "Disc threshold" is cranked all the way.

[sukri01]

i have made 2.. but performance is very bad.. just a few inches for a coin and shattering sound when i swing..

[Davor]

BTW, I realised that I'm quite happy with discrimination settings fixed to both Fe and non-Fe just overlapping at foil (dual tone), so I'll be able to replace potentiometers with trimmers, and use the discrimination potentiometers for beach/dry land GB instead.

[Davor]

It is not that complicated, so why don't you simply make it yourself?

[sukri01]

hi... does anyone here got igsl coil for sale? i'm making the first version igsl

[Davor]

That's about it. There is, however, a situation of abrupt phase change, as the ferrous and non-ferrous metals differ in their behaviour regarding orientation. So for example a small Croatian change, which is in fact shiny metal plated iron junk, gives non ferrous response when laying flat, while perpendicular position sounds ferrous, and while waving a coil approaching and departing coil over a coin laying flat gives ferrous response, and in a middle it gives non-ferrous sound. In effect such junk coin gives abrupt phase change and abrupt tone play. Same happens with other combinations of metals. It is more difficult to hide something this way.

[simonbaker]

It simply discriminates two separate quadrants, and these quadrants may overlap creating a "third tone" that is very useful for recognising foil, small gold, and tin plated thrash, as it does not lose sensitivity at the discrimination border. The quadrants can be set apart and then you have a gap in between, or a notch, but this feature is less useful than the previous one. With my gain stage mods the recovery speed becomes so fast that you can hear both tones in succession with iron cored coins, making them easily distinguishable.

I like these features. IMHO it is much better being aware of iron than obliterating it by more common single channel discrimination. A large iron artefact is a good find.

I agree what it does, and to elaborate that: the coil only detects a single signal with a single amplitude and phase (assuming targets are not spatially separated).

A piece of silver directly on top of a piece of iron will give a signal -- but is that signal unique in some way to identify the two metals? I think not -- the signal could be the same as a single piece of some other metal. You cannot separate phases the way you can separate frequencies, because there are many combinations of two signals which can sum to the same amplitude and phase.

So if you set your disc knobs for "overlap", then a target in the overlap area could be: 1) iron, or 2) silver, or 3) iron + silver. You don't know which.

If you are looking for both iron and precious metals, you don't need discrimination. Why would you need to know? You're going to dig anyway.

That is "devil's advocate" reasoning of course. In reality, I do see some advantage to knowing, particularly when evaluating the size of a target. A 2 meter iron target may mean junk (like a buried car) whereas a 2 meter silver target could be very interesting, and at the same time a small iron target may be interesting. So the extra info is useful there. Also, you "hear" the amount of junk in your search area, which can be useful for guiding your search.

But I think some people may get the impression that the "two-tone" beep indicates two different metals overlapping, which is possible but not guaranteed. Just checking to make sure that is correct understanding.

-SB

[Davor]

It simply discriminates two separate quadrants, and these quadrants may overlap creating a "third tone" that is very useful for recognising foil, small gold, and tin plated thrash, as it does not lose sensitivity at the discrimination border. The quadrants can be set apart and then you have a gap in between, or a notch, but this feature is less useful than the previous one. With my gain stage mods the recovery speed becomes so fast that you can hear both tones in succession with iron cored coins, making them easily distinguishable.

I like these features. IMHO it is much better being aware of iron than obliterating it by more common single channel discrimination. A large iron artefact is a good find.