CHANCE PI CIRCUIT DIAGRAM NEEDED

[Waikiki_Sweep]

Do not all detectors have different responses to the same targets in different orientations? For example a gold ring parallel vs. edge on to a coil?

Dan

For VLF detectors with target ID, Fisher multi frequency machines, Minelab FSB/BBS detectors change of orientation of target mostly changing detection depth or signal strength but they can identify target properly and sure correctly reject iron without questions. If you try to build same technology with monocoil different orientation of target may sometimes gives you opposite outcomes like coin turns to be iron or nail to be coin because without two coils there is no way to implement induction balance properly. It is just my point of view I keep after reading some reports on forums. Also VLF machines I own works perfect and providing correct target ID's with any target orientation and all they build with separated TX/RX balanced coils.

If you have a Chance MD on your hands can you give us some data how it behaves for targets in different positions?

[baum7154]

I'll try a few targets of different metals and see how metal identification is affected by orientation.

[baum7154]

OK just did some tests as follows:

Silver dime flat to coil IDs as silver///Edge to coil (default is left gold/alum end of scale) IDs as gold when IN CENTER OF COIL, but as silver when moved OFF CENTER but still in coil.

10k gold ring flat to coil IDs as gold//edge to coil IDs as gold

1" square of .001" aluminum flat to coil IDs as alum/gold//edge to coil IDs as alum/gold

US full copper penny flat to coil IDs as copper// edge to coil IDs as left default (gold) WHEN IN CENTER OF COIL, but as copper when moved OFF CENTER but still in coil

Note: On the 'edge on' readings ID is somewhat jumpy until 5 units or more of signal strength is reached. However with silver and copper on edge and IN THE CENTER OF THE COIL they still represented as gold/alum even at 8 units of signal strength. As the target is moved off center 1.5 to 2" then the display represents the proper metal type.

Interesting…I'd like to hear the rational explanation!

Regards,

Dan

[Waikiki_Sweep]

Results looks great. Looks like your detector works perfectly.
But all tests were for colored metals. How about ferric targets? Hair pins, beer caps, nails?

You have a great success in building fast coil. Did you shielded it? Is there shield on coil cable? How about waterproofing?
I am very much interesting to build a Chance after your target tests!!!!!
But what happens to it once I dive with it into my lovely Pacific Ocean. Can't even imaging!

[baum7154]

'Perfect' operation is a 'stretch' but it works well enough to do what I need it to do.

I will run a couple of iron things tonight and post results on that.

The coil self shields to a degree I believe due to it's geometry. The coil details are in the COILS FORUM with the title CHANCE PI COIL.
The cable is essentially a twisted pair of the coil wire, heavily jacketed but with no other shielding.

I'm afraid this detector will go pfffft once it hits your beautiful ocean...sorry I can't help with waterproofing!

Mahalo!

Dan

[Waikiki_Sweep]

I'm afraid this detector will go pfffft once it hits your beautiful ocean...sorry I can't help with waterproofing!

There is no problem with waterproofing. I can waterproof anything by myself.

Problem is:

As I see you build a very nice coil and it has very low internal capacitance because of air inside.
To waterproof similar coil I have to fill it with some dielectric instead of air. Because air (or vacuum) is a best
dielectric so internal capacitance will rise. Also salt water is perfect conductor, so I will have to build
a good shield around coil or every change in level of water will play music in my detector.
Same situation is for unshielded twisted pair that have to be shielded to ground capacitive charges
it will exchange with salt water around.
As result I will have a significant rise of coil/cable capacitance and I doubt will Chance works at all.
Also if salt water acts as target (like foil) how it will identify other targets in presents of such powerful target.

Only experiments probably can tell me if it all doable. But right now
I am feeling a little bit pessimistic about chance that Chance will work in salt water.

For dry sand I already have a multyfrequency VLF that gets target right and
tells difference even between cooper and zinc penny.

And thank you for targets testing with Chance. I like that results at least for air !!!

[baum7154]

I do not prospect in salt water or on beaches but many others in this forum do and from what I have read on their other threads most PI detectors for your environment do not operate much below 15us because salt water will begin to trigger below that level. CHANCE GUARD INTERVAL is adjustable above 15 us. This increase in Guard Interval timing frees you to have more capacitance in your coil and feed line. Therefore you can shield your coil more than mine is and it should work on the beach or even in the water but with the higher Guard Interval. I shielded a similar coil of this type using Graphite and varnish (about 1500 ohms per inch)and it works but does exhibit some loss of sensitivity to small gold. The feed line on that one was RG-62U coax and I believe it is about 13.5pf per foot. I don't know what targets you typically seek but it sounds like 5 to 15 grain gold flakes are out of the question in the ocean unless they are accompanied by larger nuggets or other metals.

I will let you know the results of the iron tests.

Good luck with your project!

Dan

[baum7154]

Just ran 3 iron targets: a 2" piece of .o6o" soft iron wire, a US nickel sized iron washer, and a beer bottle crown cap.

The 2" wire always registered at the iron end of the scale either parallel or pointed at the coil.

The washer registered at the iron end of the scale with a few jumping excursions to the left end at low signal level.

The crown cap is a beast and pretty much wanted to ID at the left (gold)end of the scale either edge on or flat to the coil.
I tried all the Iron Masks and it did not change the indication at the Gold end of the scale though it did quiet the audio response below a certain signal threshold.

I should note that I once dug up a rusty razor blade that ID'd at the gold end of the scale too.

Hope this helps!

Dan

[Waikiki_Sweep]

Looks like you got best results from Chance I ever heard. Good Job!!!
Many others blaming on numerous errors in target identification.

Probably you have assembled it correctly, with quality parts and coil is most tricky part of it.
Good coil is required to get precise results. Also knowledge how to setup and use that detector is essential.

So far, so good. I can see that your Chance acting just like a good VLF machine but with PI advantages.
So it serves its purpose of creation.

I am collecting components to build it already.

Regarding results, they fits classic VDI scale you can find in most VLF detectors.
That beer bottle crown caps got that designers from Whites and Fisher scratching their heads too
You can find that shameless piece of rust just at the center of color metals sector, near penny and gold rings in official VDI scales:



At least some VLF's like Garrett ACE 250 can read beer caps as iron.
ACE was my first machine and I still feeling that it is a best ever created MD.

Any way your results with Chance are very impressive.

Good Luck and Happy Hunting!

[baum7154]

Yes that crown cap threw me for a loop too! However I don't rely too much on the discrimination anyhow. It would be nice if they were 100% trust worthy but they are not ,so if they indicate 'gold ' I pretty much have to dig it! I have a very impressive aluminum junk dig collection and now I am looking forward to adding some sweet crown caps to it. Seriously though it will be a few more months here before I can really ring out this detector on the dredge piles and mining areas. Hopefully it will prove to be worthwhile.

I am building a second CHANCE for a friend and that will keep me busy till the spring thaw. I would be interested in getting another kit from Silverdog if he offers another batch.

Regards'

Dan

[Bardia]

New pcb

Hi i dont have any cam and i am vary busy please wait for 3 or 5 day

[Waikiki_Sweep]

Also Minelab detectors using that same patent and technology which Chance MD tried are good to report beer caps and other questionable iron as ferric.
So I still have doubts about may-be better results are connected with use of separated balanced RX/TX coils in those detectors instead of monocoil in Chance.
Or they just processing data more accurately.

I am so jumpy about that beer caps because mingy local government and greedy hotel corporations have removed trash cans from my beach recently.
So now tourists sitting on the beach drinking beer and shooting that beer caps to the water in biblical proportions.

If Chance is such a fantastic machine and it is relatively easy to build I have no idea why attention to it cools down in public last years.
No PCB's on sale, no kits, no hex upgrades, no new posts.

[WM6]

No PCB's on sale, no kits, no hex upgrades, no new posts.

I still have two (2) Silverdogs Pro-made Chance PCB-s surplus, (PCBs only - no kits).
14,70 EURO per piece - registered shipping inclusive. I take Paypal payment only.
Shipment will be sent to buyers Paypal address only.
If you are interested in it, PM me for Paypal account.

[baum7154]

I really did not have a fully integrated CHANCE detector until last September so could not contribute much to the discussions on CHANCE. The lack of source code certainly causes the design to be bypassed by many. That said, the reason I chose to build it was that it was available as a board/kit in 2010/2011, is a PI machine, is micro controlled, has a VDI, can be upgraded with software revision, has some discrimination, and interesting audio.

The initial software was really bad which I'm sure also disillusioned potential builders and the bad news on performance spread quickly. Then at least two more software versions were also failures which further drove a stake in the heart of the project. Eventually software version 1.2.1 was released August 18, 2011 and it has proven to finally work.

I can't tell you how many people still think CHANCE is a bust, but when you get to the details of what software they have it is not V1.2.1. It takes a lot of communication to over come more than a year and a half of initial design failures and many people have put their CHANCE projects in the junk box. The good thing is that all it takes to resurrect them is a few hardware updates to the original boards and to plug in a V1.2.1 programmed ATMEGA chip. To make it really begin to perform and depending on the targets they seek, they must also abandon the author's original coil, damping resistor, and coil specs. These three things were enshrined early on in the project development...'It will not perform without adherence to the original coil design'. You may very well have something in your separate TX/RX coils modification.

I have been building/modifying CHANCE intermittently since late 2010 including a lot of monocoil development for the machine. The goal has always been small gold detection. I look forward to developing a few specialized coils to add to CHANCE's capabilities. I also have a few software change recommendations for F_Andy at a later date but don't know if he is even taking them anymore. I do check his site often for more recent software changes but V1.2.1 is it for now. There are only a few of us on the forum who have posted on CHANCE since 2011 so I can see why you perceive it's cooled down. For me the success of CHANCE will be confirmed or denied in the field, in the ground, and in the tangible targets recovered.

I'll try to post a picture of my CHANCE tonight.

Mahalo

Dan

[baum7154]

Pictures of my CHANCE PI