Charcoal for coil shielding material

[6666]

Good links KT315.

Also look in your hardware store for the little plastic bottles of graphite powder, they have a long thin nozzle they are for squirting the powder into key locks.

For extra cheap method ,you can also use the black manganese dioxide from extra heavy duty carbon zinc D size batteries.
Try and get the extra heavy duty type as they apparently put in extra chemicals to make it more conductive.

Any how its very dirty stuff and needs to be washed.

Empty the manganese dioxide from the battery into a bowl, add lots of water , give it a good stir and let settle for couple of hours, the manganese dioxide will drop to bottom of bowl, when settled pour off the water, refill with more clean water.

Wash several times and then let the manganese dioxide dry in the sun etc, will take a few days to dry to powder, stir it and spread it out daily to dry faster. Or gently warm it by heater.
Be warned its very messy when dry powder, cover your nose and mouth when working with it, before adding to varnish , put it through a sieve, like a fine tea strainer to get any lumpy bits out !

Try varnish and manganese dioxide, in 1:4, 1:2, 1:1 ratio you should get fairly low resistance, I used some multi strand wire , and spread the 5 wires, taped them down, and painted over the wire, let dry completely, I was happy with result.

[jladre]

Good links KT315.

Also look in your hardware store for the little plastic bottles of graphite powder, they have a long thin nozzle they are for squirting the powder into key locks.

For extra cheap method ,you can also use the black manganese dioxide from extra heavy duty carbon zinc D size batteries.
Try and get the extra heavy duty type as they apparently put in extra chemicals to make it more conductive.

Any how its very dirty stuff and needs to be washed.

Empty the manganese dioxide from the battery into a bowl, add lots of water , give it a good stir and let settle for couple of hours, the manganese dioxide will drop to bottom of bowl, when settled pour off the water, refill with more clean water.

Wash several times and then let the manganese dioxide dry in the sun etc, will take a few days to dry to powder, stir it and spread it out daily to dry faster. Or gently warm it by heater.
Be warned its very messy when dry powder, cover your nose and mouth when working with it, before adding to varnish , put it through a sieve, like a fine tea strainer to get any lumpy bits out !

Try varnish and manganese dioxide, in 1:4, 1:2, 1:1 ratio you should get fairly low resistance, I used some multi strand wire , and spread the 5 wires, taped them down, and painted over the wire, let dry completely, I was happy with result.

Hi 6666! Thanks for the tip. It is easy for me to have that way because our local lumber maker used those manganese mix with water as a straight line marker when cutting wood.

[6666]

Hi 6666! Thanks for the tip. It is easy for me to have that way because our local lumber maker used those manganese mix with water as a straight line marker when cutting wood.

Check it out, see if the type they use is conductive you might be lucky

[jladre]

I just finish the charcoal mix with wood glue. Is that good to have a reading of 2.2k ohms from end to end of the coil shell or it need to be an open circuit? And does it really need a gap? Because i believe that using non metal shield dont need that gap..

[6666]

I just finish the charcoal mix with wood glue

What did you use for the charcoal ?,

[jladre]

What did you use for the charcoal ?,

A water base glue. Why?

[6666]

A water base glue. Why?

What I was trying to ask was did you actually use charcoal or something else, not the glue.

[jladre]

What I was trying to ask was did you actually use charcoal or something else, not the glue.

results is the machine is very stable, can crank the sensitivity to max, threshold can be heard without falsing. But sensitivity to target drops up to 30%.

[kt315]

6666, i find those rods much around in the fields. we have first world war and slightly second here.
but Australia... i do not know about it nothing. try hunting on old sites. we have first world war and slightly second here.
http://www.geotech1.com/forums/album...chmentid=40589
your theorethical story is good... but i am not theoretic, i am practic.

yours

[Wahyu]

[ATTACH]40588[/ATTACH] results is the machine is very stable, can crank the sensitivity to max, threshold can be heard without falsing. But sensitivity to target drops up to 30%.

Hi jladre, thats P.I coil? After shield have you been check decay again?

[jladre]

Hi jladre, thats P.I coil? After shield have you been check decay again?

Yes it is a pi coil. I don't check the decay. Im frustrated of the results. I think i need to gamble on graphite.

[jladre]

Hi jladre, thats P.I coil? After shield have you been check decay again?

Yes it is a pi coil.. i hav'nt check the decay..i remove those black charcoal. I think i just put to thick on to it thats why it ruin the depth.

[6666]

Yes it is a pi coil.. i hav'nt check the decay..i remove those black charcoal. I think i just put to thick on to it thats why it ruin the depth.

jladre what was the source of the charcoal ?, I'm no expert on this but maybe the low 2K resistance could be starting to act like a shorted turn , if you are going to remove the charcoal shield it could be worth first cutting a small gap and retesting the depth, or remove the charcoal shield and reduce the amount of charcoal in the glue mix to increase the resistance.

[dfbowers]

Use epoxy resin (used for impregnating fiberglass) and add graphite powder (you can get it from art supplies stores , they use it for painting) until it is very thick , but still flows as a liquid. I got good results with this method. And if you manually adjust the earth field elimination circuit width , no more false signals from earth's field. Tried it on surf pi 1.2 which detects earth field if not tuned properly and with poor shielding.

I really like this idea except I would uses a slow cure potting compound like MG chemicals 832b or MAX a/b. Since most completed search heads are potted anyway. Does anyone have an idea of ideal mixing ratios of graphite?
Don..

[Ferric Toes]

Nickel plated copper woven fabric tape.

I have found some conductive fabric tape that works extremely well and is very reasonably priced in various widths. It is item 262159780594 on ebay. Wrap around coil but leave a gap to prevent shorted turn and connect with a drain wire under the adhesive. I used a 15cm length of 7/0.2 stranded pvc insulated wire with 75mm stripped, splayed out slightly and under the start (or end) of the shielding layer. The connection from the drain wire to the tape surface measured 0.1 ohms, which is good. To the far end of the shield at the gap it measured 0.5 ohms to the drain wire.

Eric.