Ground balance add on board for Mini pulse .

[Tibuck19]

hey godigit, nah, I just did the final mod that digger did. removed the 1M trimmer and left a 1k/5.6n for the 3us on the first sample and used a 50k pot for the panel for the 10us to 150us adjust. I got it all hooked up and it is working as we speak. Although, using a board that is on the bench and a coil hanging from the ceiling isn't going to be good for testing. I will check the measurements today sometime to double check that it is at the estimated 3us/190us and check the pot adjust for its range as well.

It definitely changed how my bench mpp operates and it seems very touchy to adjust with the krinaz mods I have done to it. At full open on the 50k pot it seems to give it a similar sound to a minelab, it wobbles somewhat and seems to have a higher tone as the object being detected gets closer then it disappears. At full closed it definitely loses depth in detection and almost acts like an SAT pot but super fast. Detection lost is variable depending on the target used but it seems a fair compromise if it handles hot ground. My air detection depth with a US nickel without the ground balance plugged in was at 10 inches. With the ground balance plugged in that drops to right around 5/6 inches so roughly half lost.

I think really the only way to test it is to box it up and take it out to the field for a true ground test which unfortunately I wont be able to do right now. It would be easier to modify one of my other mpp's that is already done then to box this one up...lol

I'll keep messing with it though.. Anxious to see how your board comes out too. I assume you have left it with the original digger drawing with the trimmers on board???

[ATTACH]44862[/ATTACH]

Do you have the means to post a initial video while its on the bench , And sounding like a minelab as bonus! is it not lol

[geoscash1]

Do you have the means to post a initial video while its on the bench , And sounding like a minelab as bonus! is it not lol

Hi Tibuck,

Yep, here you go. It definitely changed how the vco acts during detection. Im using an 8x10 3dss 7 strand teflon wired coil with my delay set to min 7us, full sat and sensitivity set to 75%. The threshold is a little erratic but its because of the double tube flo light 3ft above me.

Anyway, the ground balance is direct wired to the mpp with no on/off. I havent added a switch yet since im just bench testing.

This vid is just to show how it changed the audio. I guess its not really minelab sounding but does have that warbly sound when target is directly under the coil.

https://youtu.be/eOFy_AXH4tY

[Tibuck19]

Hi Tibuck,

Yep, here you go. It definitely changed how the vco acts during detection. Im using an 8x10 3dss 7 strand teflon wired coil with my delay set to min 7us, full sat and sensitivity set to 75%. The threshold is a little erratic but its because of the double tube flo light 3ft above me.

Anyway, the ground balance is direct wired to the mpp with no on/off. I havent added a switch yet since im just bench testing.

This vid is just to show how it changed the audio. I guess its not really minelab sounding but does have that warbly sound when target is directly under the coil.

https://youtu.be/eOFy_AXH4tY

My mmp always had that Audio when anything things is detected less the 5 inches away from the coil, it started having that sound when I change R7 and R8 to trimpots, and tweaked the values, Going by memory, R7 is set at 2K or 2.5K and R8 at 19K if I remember right, Pretty much what the MMP beach Rev E, has going on now. What I like about the Minelab is the humming sound it does while its searching , The tick tick tick of the MMP drives me nuts! Funny thing to say but, I feel the chattering in my teeth when im detecting with the head phones on. Your a lucky Guy your in California, you will be able to go outside and test the GB! If you see French Canadian couple, Say hi, it might be my sister and brother in-law, their there on their sailboat for the winter.

[godigit1]

Hi Geoscash,
It definatly sounds a bit off from mine but ive not done any Krnaz mods to it yet also my bench Mpp is stock.
Sound like the target hole is pretty big as most the coins dissapear and the nugget has a almost normal gain as the it aproaches the coil. Thats positive..
Diggers Schematic is the Mpp Schem with just a few value changes . I think my board is going to act the same way when I get it up and running.
So first thought is Digger was running 10 to 150 us on the sample and your at 7us I wonder if this may be enuf to throw things off a little. Im not sure totally how it works but if his set up with the fixe dresistor and the 5.6pf cap was for 10us min and a 3 us delay for ground balance, And your running at 7us does that mean the GB offset is 6us now?? Digger if I remember right did say tuning was much harder.

I think Im going to throw in a pot there seems like we may have to tweak it for each individual Mpp maybe.

[geoscash1]

Hi Geoscash,
It definatly sounds a bit off from mine but ive not done any Krnaz mods to it yet also my bench Mpp is stock.
Sound like the target hole is pretty big as most the coins dissapear and the nugget has a almost normal gain as the it aproaches the coil. Thats positive..
Diggers Schematic is the Mpp Schem with just a few value changes . I think my board is going to act the same way when I get it up and running.
So first thought is Digger was running 10 to 150 us on the sample and your at 7us I wonder if this may be enuf to throw things off a little. Im not sure totally how it works but if his set up with the fixe dresistor and the 5.6pf cap was for 10us min and a 3 us delay for ground balance, And your running at 7us does that mean the GB offset is 6us now?? Digger if I remember right did say tuning was much harder.

I think Im going to throw in a pot there seems like we may have to tweak it for each individual Mpp maybe.

Those are good questions and I did think about that when I used his mod values.

The way I understood his setup, with the 1k/5.6pf for 3us is it would take the GB sample 3us after the main sample was done. So I was under the impression even with my delay set to 7us the GB sample would still be taken following that.

I hadnt thought much more about it since he mentioned it would parallel the primary board functions.

Now after I had built it, I remembered my main tx pulse is set to 42us so the second GB sample would need different values to line up with that portion or the 2nd GB sample would be well beyond the next pulse. So I used a 1k with the 10N but that is still probably to far out.

Im horrible with the calculating the math/figures so Im more than likely using the wrong resistor value for the second GB sample. For the width, using a 50k pot should still be close since it replaced the series 22k. I have tried a few different pots there and am using a 10k now and it seems the adjustment is better.

But, its still not quite right and like you said, there is a big hole. But I did notice I can make it go negative meaning the detection sound goes silent as the target gets closer or passed by the coil. The good part, the nuggets I have to test with are all still detected no matter where I set the ground balance pot.

The other issue so far is I am unable to turn the GB off. If I disco the 0v and/or the -5 the main board (my mpp) no longer detects anything and goes to a steady slow ticking.

I tried disconnecting the 0v and the wire going to tp7 as well and it does the same thing so I can only assume since the add on j113's being soldered on and still connected with the C/D wires it must cause a total timing issue. So we would need to figure that out.
Im still playing around with it and will keep adjusting values to see what I can come up.

[green]

http://www.geotech1.com/forums/attac...2&d=1545232767

An example of times I needed to balance ground with my PI when changing first delay time. Your times could be different but gives ballpark ratios. Greater the first delay, less the ratio(ground sample/target sample). Ground decays faster than 1/T with my detector making the ratio higher than it would if decay was 1/T. Reducing second delay to 3usec should reduce the ratio a small amount.

[godigit1]

Hi Geoscash
I think I may have figured out at least one of our problems.
I finally have a working sample generator.
I had a extra MPP beach board I had bought when I ordered my kit so I figured that was the perfect proto platform for working out this circut.
With the Mpp Beach board adding another integrator may be easier if needed.

So first thing.
On Diggers drawing at C and D outputs he draws a connection to -5 via pots. These were deleted acording to his post so both thos circuts dont need to be pulled to -5.

Next thing is he has it triggered from tp 7.
I tried tp 7 but the timings are way out .
Best place to trigger Is at tp5 as far as I can tell.

Triggering at tp 5 with my MPP 1st sample delay set to 10 us and second delat at 114us with a sample duration of 52 us.
On the GB board my first sample delay is at 16us and second sample is at 128us. Sample widths are adjustable from 58 us to 234us
The other benefit to using tp5 is that the sample delay is adjustable in unison with the sample delay pot.

I still have to dial in the timings to get the 3 us delay, right now its at 6 and the sample withs are a little fat.

Can anyone tell me what the pulse duration should be of the ground balance samples? On diggers drawing it shows a -5 ?
Im not sure if thats a error of we want a 5us pulse.

Thanks for all the help on this project guys.

[6666]

You lost me 6666, What 4011 ??? ... the mpp doesn't have a 4011 nor does the GB circuit from digger429 that is being used here.

My questions still stand as far as a couple of digger429's connections on his schematic, cant tell if they are just resistors to -5v or if they are supposed to be trimmers, also the pot after/around the 22k resistor, I think that 22k can be eliminated and a 50k panel pot used in that position but I could be wrong.

I want to work digger429's circuit into the mmp full schematic that way I can just have a board made with all components on it instead of using an addon board. I love my mpp but it is terrible in hot ground so am hoping this may help it out a bit even if losing some depth/sensitivity. I have the circuit drawn up but want to make sure of a few of his connections before doing a board for it.

I thought you were using Davors ground balance circuit, dont know why I thought this.

I

[godigit1]

Ive got it all hooked up and it works but I know the timings are not right .
Also was wrong about triggering off tp5 Im still trying to learn all this.
Ive tried moving samples around a bit and so far I cant get it totally correct.

Here is a drawing of where I have the timings at now!



The top row is where I started out with diggers component values.
Bottom row is where things are now.

I changed the R11 resistor to 2.2k and made the Gb sample abjustable down to 10us with a range to 74us.
Added a 10 k pot in place of R10 but, this gives me some adjustment to second sampe spacing but I need to be able to move it more.
Im using a MPP beach as the Gb board everything works but im not able to get any adjustment from pl 6. Ive added the 1 k resistor as suggested and kept the pot and for c8 I have a 5pf cap.
Unpluging this cap makes no difference with any of the timings.

Performance actually seems just slightly better with the GB turned on but with the GB turned off the MPP samples are being broadcast to the GB board. Doesnt effect performance but a half amplitude timing matched signal is feeding back to the GB board. Someway to isolate them would be good or maybe a switch there as well.
I still need to get some hot ground to test with as well so I dont have any results for if its actually working or not .
My guess by the timings is its not.



I would like to get the timing as close to Carls example in post#68 of the Ground balance Thread where Davor introduces his GB solution.

Post#
Im still trying to learn just how things work so if someone could help me with a couple questions It would be greatly appreciated.

What components should I adjust to specifically move sample spacing both for target and EF independatly?

And not so related but related On Davors GB circut,
Does this gb module completly replace the sample timing on the minipulse or just piggy back on?

And on connection of his GB circut is VDD reference to -5?

I have all the components to build his balance module as well and it looks really good so since Im in learning mode, might as well try that as well.

Thanks

[Davor]

Hi guys, long time...

Just a quick note. All GB schemes, including mine, work by means of splitting the tau range into two, one positive, one negative, and a zero in between them. Because of dual polarity, the simple detectors that have only a positive signal detection will not see the negative values. Detectors that come with GB all have an absolute value circuit prior to sound generation, but all of them have a zero. Fighting a zero is possible if there are two signal paths, so zero in one path will not affect the other channel. It all makes things more complicated, and detection near a zero loses sensitivity.
In case you are after small gold, a simple scheme without absolute value will be good, since all detection happens on the positive side of a signal.

[godigit1]

Hi Davore.
Thank you for checking in on this thread.
On your Gb Board you designed it with the MPP in mind if I remember correclty.
were you ever able to implement it on to your Mpp build?
Ive looked around and cant find anything on the forum. I was wondering if it worked out ok for you?

I now have the Mpp sample generator and add on completly adjustable so I can play with any timing schem I want.
Where I left off it was working OK
I have to revisite the project Ive been side tracked a little and needed to learn a little before moving on I think Im almost there.

I was thinking about another channel and implementing it somewhere down the line. Is there a example of a simplified absolute balance circut on the forum that you can point me too?
Thanks again!

[Teleno]

I would like to get the timing as close to Carls example in post#68 of the Ground balance Thread where Davor introduces his GB solution.

Post#

Too many pulses. Within 1 period the EFis actually equivalent to amplifier offset. Cancel the offset when SW4 is high and you don't need any iffy differential integrators that require tight tolerances. A simple integrator is then good enough. You also don't need to separately cancel EF for the ground balance.

[waltr]

I was thinking about another channel and implementing it somewhere down the line. Is there a example of a simplified absolute balance circut on the forum that you can point me too?
Thanks again!

There has been much discussion of various GEB methods.

I used the Three Sample method on my HH2 and it works very well without any mods to the analog differenctial integrator.
Read about his method (with links to original discussions) in my thread here:
https://www.geotech1.com/forums/show...ake-on-the-HH2

I do use a microprocessor to generate all timing pulses and user adjustments. This allows easy to change methods without messing with all those hardware timing chips, multiple channels, etc.
I do not understand why everyone keeps using these timing chips that are a mess to make changes.

[green]

https://www.geotech1.com/forums/showthread.php?24251-My-take-on-the-HH2[/URL]

I do use a microprocessor to generate all timing pulses and user adjustments. This allows easy to change methods without messing with all those hardware timing chips, multiple channels, etc.
I do not understand why everyone keeps using these timing chips that are a mess to make changes.

Why I used timing chips. ITMD suggested building coils and detector circuits might be difficult. Since I didn't know how to code micro's and knew nothing about PI's I decided to stay with timing chips and try to learn two just things. I can see it would be a lot less wiring.

[Davor]

Hi godigit1, a few answers...

>were you ever able to implement it on to your Mpp build?
No. I made a GB circuit and tested it, but many other things came with higher priority. Heck, even MPP is still unfinished.

>Ive been side tracked a little
A story of my life, but I'm not complaining. Life is good

>Is there a example of a simplified absolute balance circut on the forum that you can point me too?
Pick any. Practically all solutions work with 2 opamps, and it can be piggybacked to MPP. The other solution would be using a through zero VCO, which is even more complex, so absolute value that is.