shielding concentric

[lamoiz]

Yes
it is a foam, attached to insulate the window 10 * 5mm .. glued with double sided

[dbanner]

Looking quite nice your search coil. Can you say what material used for spacing in coil?

[lamoiz]

oupss for an IDX PRO silverdog .....

[lamoiz]

good evening Ripsdevala
the tx coil measures 30 cm and 0.585mh made of 0.75mm wires tuned with 1uf ... 26.75 turns.1.2 ohm
the coil rx measures 15 cm and 36.5 mh made up of 0.25mm wires tuned with 33nf ... 318 towers.56 ohm
the coil bx around rx about 6.2 turns with 0.75 mm.
the shielding is realized with graphite paint for guitar cavity. At the longest distance between the shielding of the cable and the coil the resistance is 2kohm but on average rather than 1 kohm.
its total mass with the epoxy resin is 520 grm ... much too much ...
here is all the info of this reel .. that works really well
bye

[ripsdevala]

Hi lamoisz, what is your diameter of Tx and Rx, wire thickness, i just experiment with big concentric but fail

[lamoiz]

Good evening everyone
I poured the glue last night. araldite 2020 with micro balls.
the top shield is not in place yet, but I did another test on the grass.
the result is rather good .. there have been some false signals but very little compared to the first time.
tomorrow night I spend a layer of guitar cavity shielding paint on top and then re test it ...

[lamoiz]

black in the background .. it's graphite paint ... it covers the bottom and the edges ..

[lamoiz]

Good evening
after manufacturing the coil holder and graphite paint from the bottom, the resistance is 400 to 1.5k end to end.
I decided to test in the wet grass .. just to see .... there is a multitude of false signals ...... more the coil reacts to the slightest vibration ...... I am really disappointed ....
ok it is not yet the resin that will surround the windings .... ok the shielding is not instalé .... but on my work plan, it ad excelentes discrimination .. selectivity and great distance of detection.1 eur at 30 cm ... gold ring at 20 cm
I do not know what to do for this shield. does anyone have an idea ??
thank you..

[dbanner]

And finally excellent video, very informative. Interesting how the outside of coil housing is shielded. https://www.youtube.com/watch?v=RtA1iVOBquA

[Koala]

I have no problems at 1k from one side of the coil to the other.

Then again there much more surface area on a my fully enclosed coil. If that makes a difference.

[dbanner]

Seems that drain wire also lowers resistance.

[dbanner]

Here the same guy mixes his graphite powder and shows you how. Very interesting. https://www.youtube.com/watch?v=SqM6eWwLIUs

[dbanner]

I was wrong about 1.5kohm it seems, very wrong. It seems you have to get the resistance down to around 500ohms by adding more graphite to mixture( the lower the resistance, the better). This video I found is very good at explaining it all. And he even explains what he did in great detail with his coil. https://www.youtube.com/watch?v=QrG_sXSybM4

[green]

my first test with white wood glue and graphite gave 1.5k per cm. this was a failure. suddenly I do not understand what ohmic value I must take into account ... 20 ... 500 .... 1.5k .... ???

Don't know what works best. I use EZ-SLIDE graphite based coating, usually measures 200 to 500 ohms as I poke different locations. Seems to work for me.

[lamoiz]

my first test with white wood glue and graphite gave 1.5k per cm. this was a failure. suddenly I do not understand what ohmic value I must take into account ... 20 ... 500 .... 1.5k .... ???