IDX-PRO+VDI

[Valters]

In my first DD coil I use foil tape, I get ~30cm on 1Euro. Now i build second coil, if i use a graphite and X mix, then i can get better sens (it can see deeper)?

[hoadlies]

Hi Barry, what resistance do you get with it?

Did you do a square test card.

steve

HI STEVE & ALL ,,

STEVE I sampled mixes on a strip of 1'' wide MICROPORE -TAPE [Hospital -paper tape] It is ''very thin'' tape & sticky on one side& very strong !!! [Its hard to break-must cut it] but can nearly see though it.. not sure what it is made from but its a 3M product from Chemist..

I stuck 2'' of this tape to a plastic bench edge & brushed my mix on [Roughly 40-60 mix [60% cellulose] IT measures aprox 500ohms per 1.1/2'' of lenghth ..[No copper strips etc as the mix is very conductive Multimeter probes only on the mix after dried..

I wound 2x layers onto my Already PVC taped Coils fitted drain wire & then brushed on the Mixture ..

I do not know if I should have included a drain wire around the perimiter of coils But that's what I did [on single strand only].. may not have needed that??????.But too late now.. Maybe experiment more with the next coil ???

I also have found an Outlet for wire but only 1kilo minimum .. I will pick it up this friday in Adelaide Cost $33.00 for 1Kilo of 0.2 ..would wind many coils RX !!..

My first M/D is now starting to cost quite a bit ,but should be cheaper for the next ones,HAhaaar..
That what I tell the MISSUS ..

SQUARE-CARD TEST ??? Please explain ..

CHEERS MATE,,,,,,,,,,,, BARRY..

[golfnut]

Hi Barry, what resistance do you get with it?

Did you do a square test card.

steve

[hoadlies]

Well as we learned in the DEUX coil thread, metal inside the coil helps get better depth!

And copper coins from the 80's are the best for tuning your coil. Now you know all the
secrets about coils!!! (He He)

HI,, S/D,,, WELL mate it has a coin ''US small coin'' glued into shell plus 2x small pieces of Aluminium tape as well ,,
Its an old coil I broke up the Foam & its a OMEGA -type coil ,coil shell is OK 10'' in diam ,I can reuse the shell !!!

COULD yo Please show where the DEUX coil you refer to is located in the site !!..
The cable used is 8723 2x twisted pairs ..with the ground [shield] tied to the RX coil !!.

i see you building a nice Basket weave Coil for PI ????

CHEERS ,MATE,,,,,,,,BARRY..[PS] I finally found a good base for graphite powder it is Cellulose furniture satin clear uses a general-purpose thinners dry's quickly ..ITS called CATILAC-3000, by protech paints..
I wound 2x layers of Micropore hospital tape over my pvc taped coils & painted the mix onto that with a single strand of copper on the outer edge of coil painted over ..

Been frustrating finding a good base i tried many base types ,Wasted much of my Graphite in the proccess..

[mohandes]

Well as we learned in the DEUX coil thread, metal inside the coil helps get better depth!

And copper coins from the 80's are the best for tuning your coil. Now you know all the
secrets about coils!!! (He He)

hi , man please send that here for use all people here.
regards

[Davor]

And copper coins from the 80's are the best for tuning your coil.

Actually a synthetic target can be made with a copper coil and a choice of resistors in series to do some interesting tricks. It won't mimic iron as such. Maybe if it is combined with a ferrite it could do that as well.

[der_fisherman]

Firstly, I am still a learner in this area, very much so, but the posts here are so great to read, I may start the next coil using them...
My thoughts would be that maybe a flexible, multicore wire (or a single core for the coil, soldered to a flexible multicore for connection) needs to be placed on the TOP of the coil, before the coating, leaving a small gap of course in both the wire and the coating. If the coating has a relatively high resistance, maybe 3 or 4 wires over the top of the coil may help.......multicore spread out?
I hope that my post is not too "off Topic" and I also hope to learn better from you Guys just how a connection is made to these coatings. Maybe a picture or three?
Thanks in advance.
Andy

[Silver Dollar]

Well as we learned in the DEUX coil thread, metal inside the coil helps get better depth!

And copper coins from the 80's are the best for tuning your coil. Now you know all the
secrets about coils!!! (He He)

[hoadlies]

HI ,S/USER,, STEVE ,& ALL ,,
GREAT response to my Question.s as usual Thanks ..

Well Its up to me to experiment with some more formula's, as said above I have tried many ,but not found the Magic-one ..

I will report back on the suggestions given ,as I have cellulose clear I may give it another Go ,I tried once before but did not include drain wire in the wet mix!!! .

SOME one gave me an old commercial Coil [not branded] I tested windings & not OK for idx so I dismantled it IT is potted with Foam & foam is coated with a black graphite mixture..
Inside is a new American COIN glued to the shell ????? 1985 [could be copper ??? ].

I will pst pics later ,,

HAVE a Good one Guys Keep warm ,,,,,,,,,,,,,BARRY..

[golfnut]

Hi all, its the hardest bit of these coils the e screen,

Almost all VLF commercial coils use carbon/graphite - the options are

make a conductive paint
carbon / graphited resin / epoxy - requires low viscosity resin/epoxy for flow and allows the particles to touch .
buy conductive paint - some for guitar cavities may work.
carbon paper / card

Some stationary carbon paper isnt carbon - some is . You could get fanciful with a disc of carbon paper - not tried these

http://www.ryman.co.uk/0222010402/Ryman-Carbon-Film-Typing-A4-10-Sheets/Product?extcam=agg_gps_prod_feed_pf&istCompanyId=724692e0-2f99-4874-9565-6fc82074fe86&istItemId=xrxptwrtq&istBid=tzwt&gclid=CPSWvJbe37wCFfPItAodBUEAmA

The other thing we havent really touched on much on here, but Ive been thinking about trying one day.. Is actual carbon fibre. Woven tape or mat.
You coulld make some pretty looking strong light conductive shells with carbon.

http://www.ecfibreglasssupplies.co.uk/c-377-carbon-fibre-tape.aspx

sample some low temp carbon ink - tv remotes pads
graphene




Thick paint, epoxy gave me worst result. As thick binder holds graphite particles away from each other and you get high res.
The inverse solution should be very low viscosity paint that dries with low build - like a cellulose thinned top coat - but I cant get it in uk so cant try.

One thing I never did but may work is if your shell inner was melted using a solvent then while wet you flood with graphite powder. This may load the surface well, the solvent evaperates and the graphite it left keyed IN the sorface of the shell - with no paint/binder keeping the grapghiite particles apart. Fiddly worth a go on a scrap peice.
acetone may work with some plastics to soften surface.

Closest I got was thin epoxy - plus warmed in oven to ~60C - this lets the graphite particles settle and touch together - I got some flow, not great, 8k/sq was about 50/50 grapghite / epoxy - but I only got a good result 50% of the time - even when weighing materials out on digital scale... to the gram.


home builders did try ally foil - this does work but isnt quite so sensitive coil, can break foil if heavy handed during construction.


nickel sheild spray - never tried - should be ok - dont put on too thick or lots of layers

some use wire mesh tape - 3m make one

survival blanket - must use ones with metal on surface - the metallisation is very thin and does not support much eddy currents which is what you want - these were always thought as better than ally foil. Bit fiddly.


Do not use Upol weld thru conductive primer - is does not conduct at all.



My view is you dont want to use materials which you can see or detect with a detector - as it shows the sheild material supports eddy currents within it. You dont want this.

[sinclairuser]

barry i use clear acrylic laquer(plasicote), and the surface is not conductive the graphite paint however is, when dry sand a small patch to take the shine off if you get into it, it is conductive but when its dry its impossible to get good contact, thats why i imbed an uncoated wire in the paint from the start, a tiny piece of copper tape with a tag wire soldered on has been used by others, once its dry put one probe on the wire then sand a patch an put other probe on that, aim for 1-2k per inch.

[hoadlies]

That wet grass problem with the TGSL was a real pain in the butt. It didn't seem to matter what coil I made or how may circuits I put together. I like to hunt at night alot and wet grass is a normal thing. Keeping the shield grounding separate from the Tx and Rx coil definitely solved my headaches.

The White's grounding scheme is the same as what I came up with for the TGSL project, so you should not run into that.
Also, I was wondering how others made out with USB cabling for the White's coils. I have only tried Belden 8723 so far with the IDX project.
On a different note.. more snow here in the Eastern U.S. last night. 4 times in one week Uhh.. Snow covered with ice, covered with snow, covered with snow. Walking in the yard is a B!7(h!!!.
Don..

HI DON & ALL ,,WOW ,we here never see snow like that I guess its a Pain in the Butt with too much ,''send Some over To ''OZ''-Please HA.Haar..

OK on the cable USB-2 versus the-8723 beldin ,Query are all the shieldsX4 seperated from each-other ??? & or are the all common ?????
And seperating the 2x shields in a DD coil ?? do you terminate them at the Board ???? [I read that somewhere-else in the forum ]
Could you draw a diagram of how you connect your DD coil using the 8723 cable Please ..with the seperate shield connections ..

I have some 4xseperate- shielded cable ''BUT'' all 4x shields are common ????..

mY new wound DD coil ,with my Fibre-glass shell is coming along OK ,But have been busy doing other jobs & not finished yet ,But soon..

I have Ground -up a 500gram Jar of carbon-Graphite From some large wind-turbine Brushes ,But still experimenting with a mixture ..[Tried many differing base's laquer ,water base paint,PVA etc ,But have not found the magic solution yet [The water based household paint seems best so far ..],With some INK-JET-BLACK-ink mixed with the Graphite as a binder..

I wonder what the Basis of your Graphite Spray is ????? Water base or inflamable base as say thinners for Auto paint ,When I tried using clear Auto Laquer once dry it did not conduct ??

QUESTION-CAN I wind a ''ground wire'' say @ 1''or so spacing around ''Micropore'' paper hostpital tape'' after first wrapping the'' pvc taped'' coil,,, with the micropore & then wrap tinned- ground wire& then coat with my resistive mixture ..?????
I did this on my first coil it seemed OK... but as I had potted too much & did not get null 100%I had to bin that one & start again ,So never got to actully use it on ground surfice..

CHEERS ALL ,,,,,,,,,,,BARRY from a much cooler ''OZ''..

[Koala]

hi my friend koalai want know , do you change your detector ame last changes that Mr golfnut send for me in page 85 ( i think )when i finish Dp2 , i want change my idx like last version that Mr golfnut send here.i can not reject iron and can not reject ferrite , are you remember ?regardsand if possible say me your changes on your idx

Hi built as standard no changes.
Used the original zener diode. Felt better to me than the reverse normal diode that some used.

Yes I remember you can not reject iron or ferrite. Think you need to post pics of you board and signal trace of each channel also the phase of the TX and RX signal. Sure we can sort it out as this is a very solid metal detector and very versatile worth putting the effort into fixing.

[mohandes]

hi my friend koalai want know , do you change your detector ame last changes that Mr golfnut send for me in page 85 ( i think )when i finish Dp2 , i want change my idx like last version that Mr golfnut send here.i can not reject iron and can not reject ferrite , are you remember ?regardsand if possible say me your changes on your idx

[Koala]

it also did not like patches of rock under the sand.

Yep I have had that the damp held by rocks under the dry sand act like the boundery between dry and wet.

You can work the boundary but it's too much like hard work. Most finds are on the wet side. You have to stand with your back to the sea and swing the coil in a straight line not in an arc then shuffle you feet like a crab and only do about 1/2 meter at a time. As you keep the same dampness under the coil you can make slow progress but even this fails if you cross a gully. You normaly have to be in be all metal mode and you ears get use to the small up and down of the threshold and a target rises quicker and more consistent.

Forgot to mention that I was running at full sens on the full wet did not have to back it down at all for patchy areas I have to turn it right down for disc to work stably.

Hope everything goes well for the car and job front.