XP deus coil modification

[Funfinder]

Hi Henrik, the price of your multimeter is real good. I checked the internet - the most priceworth black-white screen LCD handheld multimeter with osci-functions
start at around 150 Euro but the most of them cost ca. 1000 Euro - this one here is 169 Euro with many accesoires:
http://www.ebay.de/itm/Uni-t-UT81B-U...-/161095586386
Uni-t UT81B USB

If I can give you a tip for your own best as an experienced treasure-hunter who has all kind of coils, from 10cm Garrett Sniper to rolling 1meter coils:
If you have found a really lucrative site or spot the best thing is to dig away first most of the not wanted stuff so you can find the often much deeper valuable stuff and often below the spots where before all kind of junk was buried. Those mini-coils are good for pretty surface-near stuff only. And against small alu- or lead-parts even the best disc has no chance.

btw. I forgot to say that perhaps the best position you have reached now could be to convince the XP company that there is a need on the market for such a small coil.
If you mail them they might be really interested for your new invention and discoveries and now they have already a good working plan how to built such coil and
perhaps they even will give you money or products for free. Maybe you wait with that until everything is completed and after you got field test results.

Good Luck.

[Skippy]

I use the 5 inch DD coil on my Fisher F75 a lot, but particularly on trashy iron-laden ground. I find the depth quite good, about 75% of the stock coils depth. I have dug coin-sized targets from 8 inches (20cm). I guess Hen's trashy ground is ploughed (plowed), so everything is mixed up, and therefore good targets are not deep, they are just as likely to be 1cm down. I am hoping that because Henriks new coil will be a dedicated small one, the front-end amplifier gain could be increased to obtain more performance. I think I have identified the circuit parts to change, but we have to get the coil working well first, before we even consider changing anything else.
Regarding screening, I will send you some notes of mine, but you should consider other ideas, particularly the graphite paint thread of SatDaveUK.

[Henrikras]

Hi all...
First forgive me If I'm not answer something.. Got some many balls in the air at the moment.
GOOD NEWS... The first turn on is just done, party time, IT WORKED.
Ive made this video... Please dont look at my mess in the workshop, I know some day I must clean up.
Link. http://www.youtube.com/watch?v=dCkoU2mn_DM&sns=em
Now I have to figure out what to do get a Null with the RX more in the middle of the Shell.

Henrik.

[Henrikras]

Thanks Funfinder. Good idea to dig a lot not wanted allso. Allready doing this with Big iron, but should from now on dig some more. Yes the prize is Very good with this China instrument. Sure not to lab work, but I'm happy with mine.
About the XP and make a contact to them.. I'll wait with that. This project is free to copy and use for everybody, Thats more funny than big XP Business. But first finish it and then out testing.

Skippy... I'm thinking about doing a test outside, before the shielding exsperiments. Something like small araldite glue points to hold the coils.. And gentle / carefull go out to see how it chattering or Maybee not !
Henrik.

[Skippy]

Commercial coils like the 11 x 7 used on Teknetics T2, Greek series, G2, Fishers etc use a small loop of wire in series with the TX coil, which is moved around to fine-tune the null. This is done after the main coils are fixed in place and stable, I think. How big this loop is depends on how far out the null is, two turns 2cm diameter might be a starting point.
When you have the polarity of the two coils correct, you will get the single 'ping' when a target is swept across the coil. If you reverse one pair, eg. the RX pair, the result is a 'double-ping', each side of the centre position. If you mark one wire of each coil with a permanent marker pen, you can make sure you wire it up repeatably during your experiments.
Don't use araldite! For temporary fixing, try blu-tac, 'Scotch tape', hot-melt glue, hard candle-wax, anything non-permanent.

[Henrikras]

Okay no araldite...
Now something Very Strange !! . Got 4 eitems, Iron, Coke, low and high conducted coins. ID Stock coils (all my 3 Stock coil) say ID iron 01-02, and Coke 25, low C - 45-50 and High C - 92.. And those IDs is memorized out searching.
BUT the 7" say coke ID 10-15 / Iron still 01-02 / low C 42-45 and high C 92..
Its seem that the 7" coil got another performance. (Maybee a Very good idea, because Deus normaly like Coke, and with lower ID it could avoid Digging coke.) Just afraid that GOLD allso will go low. That will Be tested.
tryed all, Freq., TX power, different Null (small changes of coil sharpe), and nothing change it. Coke got lower ID.
maybee the Sound respond is a little overloaded, Not sure but could Be the case. Sounded a little like the TX 1 (low power) was more smooth and nice to those low IDs from 50 and down.
need to do some more test tomorrow.
Very Strange this.
Henrik.

[Skippy]

Tricky to say why the coke responds differently. You haven't got a shield, so maybe it's picking up your hand (capacitance), try blu-tacking the coke etc to a plastic /wooden ruler then sweep it across the coil. It may be something that happens during the auto-calibration process. That's one reason it would be nice to get a broadband null, in case the machine is fussy at turn-on.

[Funfinder]

Henrikras, I wouldn't look for any contracts with XP, the whole topic remains still to them,
even if you are tinkering now around and do some pioneer-work for them.
But they may like your work and if they see that people now start to create smaller coils on their own because
there are no others available, they might think about it, and if you convince them how good it works and how many wants such a coil,
they may start to produce it and you're the hero of the whole XP Deus community!

Another topic:
If you have some spare capacitors in the range of 1pF to 50pF you should test-attach them where the coil-cable is connected -
- just connect them parallel to the single coil circuits there, perhaps 1 is enough, perhaps both coils or only the left or the right.
That way you may be able to shift the metal-ID-value upwards or lower so you don't have to make changes to the coil.

A second special opinion is creating directly a "shifted coil" which also is able to detect mineralized stones or meteorites where usually rusty iron gets detected.
Use a 5x5cm piece of high-mineralic brickstone as a test-object, if you are interested in such kind of mod.
That way you would be the first person who is able to detect such stuff with the XP Deus!

Ciao

[Henrikras]

Thanks.. Some more good advice to work with.

[Henrikras]

News.. Its going good. Hard day to find out what kind of problem the searchcoil had with the coke and low end.
Just found a Very good balance by adding 4 more turns at the RX. Now Its seem to Be easy now to find the Null and the null dont have to Be low, something 10-20mv and its working nice. Coke came up at normal ID. Properly something with phase !
Had to play with some Gold similar to Coke ID, and get the deus to give some nice signals.. That Helped a lot.
(Coke is jumping ID and difficult to work with.)
Just now the first try of shielding at the RX is drying up. Ive made a new version combinated with some old tradition Sheilding.
Graphite spray at some tape with a Very Very thin cobberwire (solderbar). Paint - Dry up - paint - Dry up, until I get around 1 kilo ohm approxly. Made a plastic tube and cut it in two parts... This is made to make the RX coil Very stable and to get a distance between the windings and the graphite (capacity). I remembered to make a tape, to avoid the Sheilding makes a loop.
No clue If this will work. If not its easy to remove and try another version.
Henrik.

[Skippy]

It's a good idea to twist the two wires from the RX coil together, from the coil to the screened cable. This will reduce EMI pickup.

[Henrikras]

Done Skippy, even they are Very short from coil to the connecting at the cable.
Its still working Very good. I'm ready to close it up. Very happy with the result so fare only indoor testing. More and more I dont think that XP got any shielding or Very little shielding, because after the shielding came on mine, its was like Night and day.
But that will some test outside tell us.
Cant Thank You all enough.
Henrik.

[sinclairuser]

the coil shielding dilemma is a strange beast, sometimes you can wind a coil (perfect specs) then adding your favourite shielding recipe totally cocks it up again, on the other hand a coil almost identical can behave differently.
i wound a small coil following on satdaveuk's experiments with a 3" coil, i call it the "hockey puck" since its identical to a puck with coil ears, this was made with a particular cornish beach in mind, where small deep pockets of fine sand lie around huge rocks, the coil itself worked excellent but was very sensitive to any bumping of the coil or waving your hand under it.
i added a carbon shield to it painted on the inside of the shell with a small drain wire, the ohms readings of the shield were going by the "book" nowhere near, but further application was not making enough of a difference to warrant adding more so i gave up and sealed the coil(thinking i'd try it anyway).
but it works it seems at least my barracuda thrives on minimal shielding, i know what your doing is not the same, but maybe this approach could help you.
when your coil is on specs and you are happy with it, add shielding as you have done (spiral wire covered with carbon), then try it adding coats untill it works as you want, when correct take a reading for future builds and seal the coil.
as it is a "new" machine in terms of coil building and no one seems to sure about the correct shield strategy, adding minimal shield and increasing it till you get the right shield seems to make sense to me.
no one made a coil for deus before, it may need a minimal shield, or a thicker one who knows, but going in blind at a fixed 1 or 2 k may be wrong, and if the shield is too heavy/strong depth will suffer, if too light/weak it will be ineffective.
ally

[Henrikras]

Thanks Sinclairuser... You so right about this, I got no clue about the perfect shielding... This is coil no.1 and Maybee there will be no.2-3-4-5 before it will Be perfect. But on the other hand, it could Be that it isn't so difficult at all.. Why! The Deus got all this electronic. ( I don't know how is working) but it seem to adjusting a lot to find its own best performance.
Last Night Sheilding ended not with 1k ! After the graphite Dryed up it was 2-3k, but it seem to do the job so I stoped with that. I know from experience that going from 2-3 k to 1 K, need a lot of paint.. And I got in mind that Deus hasn't got any sheilding, that was why I stoped.
I got some more good news. You all know how difficult it is to keep the perfect Null while the sealing is drying up.
Mine had now been drying up (I closed it last Night) some 8 hours and this morning it still with the perfect Null. It had not moved anything. This recommendation fra Donald B with the Black 2 component Compound is perfect. Thanks Don. http://www.circuitspecialists.eu/bla...ating-compound
I hope that I dare to test the searchcoil outside after work this evening.. But the sealing needs 24 hours, so it could Be stupid to try anything before its proper dry. Just in case that I need to finetune, I havn't fill the Shell up 100%, it still need some 4-5 mm.
thats why you can see the RX Very high up at the picture 1. (Maybee a little to high)
The Null is 8-10 mv PP. not bad. Picture 2.
Henrik.

[Henrikras]

Hi again...
Sorry to say it, but it didn't work at all... Chattering \ Sheilding wrong. Works perfect in lab but out at my field, signals like chattering just by small swing with the coil. Long grass gives signals, close to soil gives signals. Its not good.
What to do now !!!
One idea !!! Open to Stock coil and find out what kind of Sheilding XP had Done. Something must had been used.
Then make a new coil.

Henrik.