GOLDSCAN4 - Help

[mrezaee31]

hi,GREET

What do You idea about deeper , severance this circuit ...?

[kt315]

it's very oldie matter. use Search engine and you will see, for an example, much threads on Goldscan. is not a deeper, but 4 samples PI detector by Eric Foster, projected for gold nugget hunting only.

http://www.geotech1.com/forums/showt...light=Goldscan
http://www.geotech1.com/forums/showt...light=Goldscan
http://www.geotech1.com/forums/showt...light=Goldscan

yours

[Max]

hi,GREET

What do You idea about deeper , severance this circuit ...?

Hi,
KT315 is a bit critic about it... sure it's old stuff... old philosophy I would say, but it's powerful still today.

About sensitivity it's a big beast and will bust many actual PIs around... no matter what they use at coil... no matter of anything else than power pulses transmitted.

The GS4 it's so powerful you could detect a brick fragment like a cigarette box at 40cm and more. It's not easy to have same kind of things with other mds... even very sensitive.

But it's also a BIG, ENORMOUS drawback: it sounds with hot rocks... it sounds with fired bricks etc etc so not so good in REAL FIELD (hope you'll understand me about...).

Sure it's a fantastic PI for nugget hunting in a flat mineralized matrix (like e.g. australian deserts... where not too much hot rocks but flat red soil minerla content).

You cannot use it where fired ceramics there is; nor you can use it on e.g. black sand or in hot rock presence (fired magnetic stuff in the rock).

That's cause thermal gradients in rock (or brick etc) creation will free magnetic dipoles... that will then align all the same way like little compasses at earth magnetic field... too bad when you'll encounter that things around and have a GS4 on hand... it become erratic and crazy... sounds everywhere.

The project is really hard thing to homebrew successfully but anyway a real challenge for any md homebuilder.

I would not suggest you try mount one, unless you're a real electronic and md guru... otherwise could be disappointing much.

The schematics had minor mistakes already all solved by Alexis and other people. Also, keep in mind there's no easy , ready pcb for it in public domain... so it's challenging also for that.

But if you're a nugget hunter and have mineralized soil... have big experience in electronics also... why not ? could be intriguing somehow make one of them in that case.

Kind regards,
Max

[kt315]

Max, the man asked me privately to help. I replied, but I SHOULD NOT ANSWER on similar requests every time. I am not so active you expect and hope of.

[Max]

Max, the man asked me privately to help. I replied, but I SHOULD NOT ANSWER on similar requests every time. I am not so active you expect and hope of.

Hi,
now I understand, sorry...

nice to see you still live on teh forum anyway!

Not like me... I'm a bit... desaparecido at now...

Kind regards,
Max

[porkluvr]

Hello Max, everybody. I read what you said about the GS4 not working so well on black sand. That has me worried because I am working on a similar project. There is gold, but also plenty of the BS stuff around where I live.

Breaking my detector into two boards, I have already completed designing the power and timing board. Last night I "finalized" the receiver design, now getting ready to start PCB layout.

I know that using alternate polarity transmit pulses can prevent black sand from getting to a magnetized state. Are there any other methods available? What PI detectors would NOT magnetize black sand, and how do they do it?

I have some empty space on my 4"x6" card so I think I will try and incorporate some way of generating alternate polarity tx signals. To use two separate coil windings and two FETs seems the way do do so with the least headache. How would you do it any differently? Have you seen my proposed "Complex PI Timer" in the Modifications section? I think that I'll only need to add one or two flip flops, a few transistors (and a second coil winding) to implement alternating tx polarity. (I also need to consider tying in the receiver preamp... .)

Your input on this would be greatly appreciated.

I'll maybe go plant some tomatoes and try to think about this before I start ripping up my PCB layout. (I can chew bubblegum and walk at the same time, but that would be a trick!)

[Max]

Hello Max, everybody. I read what you said about the GS4 not working so well on black sand. That has me worried because I am working on a similar project. There is gold, but also plenty of the BS stuff around where I live.

Breaking my detector into two boards, I have already completed designing the power and timing board. Last night I "finalized" the receiver design, now getting ready to start PCB layout.

I know that using alternate polarity transmit pulses can prevent black sand from getting to a magnetized state. Are there any other methods available? What PI detectors would NOT magnetize black sand, and how do they do it?

I have some empty space on my 4"x6" card so I think I will try and incorporate some way of generating alternate polarity tx signals. To use two separate coil windings and two FETs seems the way do do so with the least headache. How would you do it any differently? Have you seen my proposed "Complex PI Timer" in the Modifications section? I think that I'll only need to add one or two flip flops, a few transistors (and a second coil winding) to implement alternating tx polarity. (I also need to consider tying in the receiver preamp... .)

Your input on this would be greatly appreciated.

I'll maybe go plant some tomatoes and try to think about this before I start ripping up my PCB layout. (I can chew bubblegum and walk at the same time, but that would be a trick!)

Hi,
yes, the double , alternating pulse is "known" as giving more reliable operations on black sand too... and mineralized places in general, where flat mineral concentration there is.

Now... I have to say, I made actually an alternated pulsed version of GS4 (but do not tell Mr. Foster about! ): not a joke , I made it really, the way you described with another coil that gives the extra tx pulse, opposite polarity.

I made it easy.... used similar components of original GS4 , same age, to be clear.... just digital ics for timing... etc... all by the book.

I have to say I made it not for the purpose of ignore black sand.... but cause wanna explore and investigate a way to reduce the influence of magnetic dipoles in fired ceramics.... but the project was a real failure under that aspect: the unit worked but no advantages e.g. reduction of false signals about fired ceramics and hot-rocks too.

Now.... I'm going to take a picture of pcb... if I could find it... to let you see what I made and make an idea of what is complexity added , it's not much stuff....(really don't remember now where I put schematics of it...unfortunately)

I was not really interested in flat-matrix behaviour when tested it on soil.... so cannot say if it was really more stable on e.g. black sand etc never tested that in such places...

Kind regards,
Max

[Max]

here it is....one trimpot adj the delay between the tx pulses... but the other ??? I forget about it!!!

Kind regards,
Max

[porkluvr]

Hi,
yes, the double , alternating pulse is "known" as giving more reliable operations on black sand too... and mineralized places in general, where flat mineral concentration there is.
Max

I hope you're right!! I'm a perfectionist so I could not be happy with myself if I was aware of a better way to do something but did not do so.

I think the dual transmitter screams for a DD coil. As for the receiver, by simply adding a second receiver preamp everything falls into place - unless there is something I overlooked. The alternative is too scary to even think about (blanking gates, coil switches OWWW).

If I were a better person I would look upon this chore as "an opportunity to excel", instead of a just a major PITA. I just hope it works - but if it doesn't I will have tried my best. (...it WILL work..) Relatively few extra components are required, but a DD coil seems necessary - the least complicated, whereas I would rather have DD as an option. In all honesty dual tx channels looks simple so I won't moan about it any more.

With my interleaved pulses timer there are two obvious options for splitting up the tx pulses; to split on each alternate cycle (1+5)|(1+5), or have the short and long pulses go to separate FETs and coils. I think for the purpose of demagnetization the first option makes sense. The second option opens the possibility of optimizing each coil/FET tx channel for different materials of interest. Either one looks very easy to implement.

I also have a LOBO that I work on in parallel with this PI. If one or the other gets too maddening then I drop it and pick up with the other.

Here is the original timer I devised:
http://www.geotech1.com/forums/showthread.php?t=15323
The dual transmitter modification should be fairly obvious so I won't bother posting its schematic. Besides, the apparent lack of interest demonstrated by folks on these forums tells me "no, No, NO!") If anybody wants the details, request by PM. I suppose it would be considered off-topic here.

I ripped up my tomato bed and have regretted it for the past three days. (PAIN!) Could barely climb out of bed today.

edit: It occurs to me that there might not be any harm in using two tx channels and simply connecting the FETs to a single coil, and using a single preamp. Time will tell

[porkluvr]

edit: It occurs to me that there might not be any harm in using two tx channels and simply connecting the FETs to a single coil, and using a single preamp.

Yes, no harm done. But it would defeat the goal of having alternating polarity tx waveform - without some trickery being employed.

[jamal]

gs4

hi all
I am question for Q3 where is connected Emitter and collector
thanks