LOOKING FOR GOLDSCAN 4 Schematic.

[greylourie]

I would add: a little microprocessor could semplify all the timing generation and audio processing of this project...

Altair, I think you have a good suggestion. But first I think the most important things to do are : implement zero offset opamps, simplify/remove some switches, improve/copy/create low noise power supply.
Once those things are successfully done, then your suggestion becomes a logical and easy step.....

This thread is full of good tips on improving the GS4. See posts by Reg, Jose, Max and others.

[Jose]

Hi Jose
Did you see this post, by JLKing in HH2 thread : http://www.geotech1.com/forums/showt...754#post120754
He said removing C24 improved response to small targets. Do you think this would work with your GS ?

Thanks greylourie.
I am using 15 pF and seems to work well instead of C24.
I think I read that Carl said it was possibly a mistake copying and pasting.
Jose

[porkluvr]

OK I renamed the pdf files and now they open no problem. Thanks, all!

[greylourie]

Hi porkluvr

You did some very nice work on a power supply for Tinkerers IB P.I. Do you think you could bash up a suitable low noise power supply replacement for the GS4 ? I'm not really au fait with electronics. I try to cut and paste, and would probably end up doing something terribly silly.

[ivconic]

I came across to this interesting idea today.
It should be pretty much "synchronized" and shouldn't involve any significant noise amount from power inverter to the rest of circuitry.
Now, the rest of GS circuitry must be adapted to this solution.
Real art would be most proper ground plane redistribution on future pcb.
Now... i am under real doubts and also very tempted to try to use "virtual ground" formed at U2-U5 stage as main pcb ground plane, instead as it was done at original GS4.
I could use others opinion on this.
This is more interesting to me than all the rests of circuitry.

[Jose]

I came across to this interesting idea today.
It should be pretty much "synchronized" and shouldn't involve any significant noise amount from power inverter to the rest of circuitry.
Now, the rest of GS circuitry must be adapted to this solution.
Real art would be most proper ground plane redistribution on future pcb.
Now... i am under real doubts and also very tempted to try to use "virtual ground" formed at U2-U5 stage as main pcb ground plane, instead as it was done at original GS4.
I could use others opinion on this.
This is more interesting to me than all the rests of circuitry.

[ATTACH]27374[/ATTACH]

Ivconic, I wonder if I could run this scheme with a duty cycle of 10% alrrededor, as befits the TX pulse GS4.
Jose

[ivconic]

Ivconic, I wonder if I could run this scheme with a duty cycle of 10% alrrededor, as befits the TX pulse GS4.
Jose

Yes good question.
Circuit is academic, shown mainly as idea, so we can talk and elaborate it more as approach.
Main problem, relating to noise at simpler PI designs, that i noticed so far; usually are discrepancy and crossing between main TX oscillator and power inverters or charge pumps, so as power&ground planes redistribution on design itself (pcb and parts).
So idea is to run TX on basic frequency but also to use same one for power inverter, no dividing, no multiplying.
The simpler power inverter - the better.
I considered use of some conventional switch, but all those are presenting huge source of noise, though some of those are frequently used in such PI designs.
This mod i am suggesting is just a principle which may be improved further.
GS4 is problematic because we have several different voltages to carry about. All those to come from same source. All those to synchronize. Problem.
So i would rather pay attention to that aspect and less to else.
Also i would like to avoid solutions like mc34063, 7660 and similar, because those are splendid noise generators on the first place!

[ivconic]

Jose how about this:

[Jose]

I like the idea of being able to control the TX pulse width independent of the source, while both synchronized.
I think the next step to consider is the power consumption.
There are other possibilities that can be condiderar, for example if it is necessary to regulate the 12 volts, or 24 V to TX, or fed directly from the battery, as does the GS5, according to the published schedule.
O also feed the TX stage 14.4 or 16 volts with inverter self-regulated in order to get something more sensitivity.
Battery and source circuits could be sepados. As you say it is good to reduce the noise as much as possible.
The possibilities are many, I think the experts can give a better review than me.
Jose

[ivconic]

I have several GS schematics drawn by various people.
None of those in format that i can edit or rearrange, usually those are PDF or JPG or similar.
So first things goes first... i had to redraw it in ExpressSCH and make it "editable" for eventual corrections or modifications.
This will be looong winter!

[Jose]

I could lower the "ExpressSCH" program. Ivconic Great job, thanks
Jose

[greylourie]

ivconic, you have a splendid approach.

Layout is key to getting noise out. Power regulation and supply can be quiet if i.c's like LT1172,LT11xx etc are used (Like in Tinkerers power supply). Doing it right could make a machine that is an improvement on the original. Question is, do we want to make this largely pdip/through hole design ? That way this can be as popular to build as some other projects here.

Although having a board with some smd elements could give a chance to further improve performance. I only see Hammerhead in smd version. Maybe another time. What are your thoughts ?

[Jose]

Hi Everyone
Here is a video of homemade GS4.
The presentation has a lot of detail, need to finish the coil, etc. improve the cane.
The purpose is to have an idea of performance.
The tests were conducted at home. The field is calmer.
The first test is all metal.
The second is the way land
The third mode is as low conductors.
The fourth is a high mode. (SEL2, modific).
Finally the pointer.
regards
Jose
Http://youtu.be/GEd9_PoW9bE

[Thomas]

Good video, excellent results. could you give a little info on the pinpointer? I was impressed.

[Jose]

Good video, excellent results. could you give a little info on the pinpointer? I was impressed.

The selector is the same as those published in the schemes of this forum. Exept the SELEC 2 mode was changed.
The modified scheme was published on page # 12 post # 284 as "GS4 Modo Alto.JPG ".
In this way, contrary to SEL1, low conduction objects as foil, gold, caps bottles, etc. are removed. and high conduction is detected. This mode is useful when trying to find coins and reject the bottle caps. Everything depends on the setting of the detector and the metal compocision.
Jose