DIY Pulse Induction Detector (Impulse III)

[Bush]

Someone turned up out of the blue & spun this link on PI detector building kit.
It may help anyone venturing into the DIY field.
https://www.worldradiohistory.com/UK/Electronics-Today-UK/ETI-How-To-Build-Gold-Detectors.pdf

 

[Bush]

Looks like the homework has been done on larger coils for the sdc.
i was out of the picture for some time . ...
Target Signal vs Amplitude in Hyperphysics.
Oh ! Well ! ... Spare working coils is not so bad.
I`ll just re-wind the windings into within original 8`` coil spec with what i have.
The 4500 might like the larger ones.
Closing Ceremonies i`d say.

With one exceptional thought.
200 x 200 piece of tin foil air tested with Minelab sdc OEM 8`` repaired coil .
Max reading of 800mm.
The modded 12`` NF air test reading maxed out at 950mm but is it sdc stable ... .

 

[Bush]

Coil Works in Progress.
1. 12`` coil foam insert.
2. New coil top & base. Armstrong bucket base & 20 liter oil tub.
3. Base & coil workings
4. Conductive painted shields.
5. 13`` Shield plate Ohms resistance test.
6. 13`` Shield 1.5 AAA battery DC volt test.
7. 8`` shield Ohms test.
8. 1940`s 8`` shield Ohms test.

Conductive Paint.
New Coil Faraday Shield Coating Formula.
Drying Agent - Automotive Acrylic Thinners 40 %.
Pigment - Graphite Powder 55 %.
Binder - Acrylic Lacquer 5 %.
4 to 5 thin coats brushed on.
Advantage over acrylic water base paints as the thinners cleans the dried surface skin of the previous coat creating better conductivity
contact and adhesion.
Required Ohms per inch is achievable.
65 - 85 ohms thereabouts.

 

[IBGold]

Conductive Paint.
New Coil Faraday Shield Coating Formula.
Drying Agent - Automotive Acrylic Thinners 40 %.
Pigment - Graphite Powder 55 %.
Binder - Acrylic Lacquer 5 %.
4 to 5 thin coats brushed on.
Advantage over acrylic water base paints as the thinners cleans the dried surface skin of the previous coat creating better conductivity
contact and adhesion.
Required Ohms per inch is achievable.
65 - 85 ohms thereabouts.

Hi Bush are you painting it on paper card? how does it go painted directly on to Styrofoam and I have not forgotten about the pictures just a bit hectic over Christmas here.

Regards, Ian.

 

[Bush]

Hi Mate,
I have not tried it on foam i think it will react with the thinners though.
I`m favoring full disc shields for the coils just my feeling that target eddys may pass through the spoke arrangement but i have no idea really.
For me to create a spoke coil in foam to test i would find most difficult regardless.

Just now finishing off a 14`` Elite rebuild i bugged some of the winding cable whilst dismantling so have decided to twin wrap it in flat wound dual cable.
Doubt it will work on the sdc but positive it will on the 4500.

Flat wound a F1A4 8`` twin layer into 9 1/2` `results so far air testing looking good & sensitive.
Another F1A4 8`` i`ve finished into 9`` standard layer wrap not tested yet.
Decide to use that white foam as the coil frame partly because i had some laying around about half the weight of the denser polystyrene stuff.
Plastic dinner plates for the casements but trying to get plastic angle for the shaft connection is proving most difficult to acquire so far best i can get is off those angles that protect hardware products in their packaging.

The cardboard / paper shield base was difficult to get the right gauge as it either is too thin prone to breakage or too ridged to bend around the foam rim.
Art supplies had a variety so picked up some various sheets including very thick blotting paper $1.50 a pop.
Pizza cardboard packaging works well but restricted to 9`` dia.

Question in my head i`m dealing with is the high & low end of the graphite coating continuity & what variables could occur.
I`m guessing excessive conductivity will result as a targeted & less will be susceptible to false ground signals.
The other idea is potentially some variables there may suit different types of ground.

Hopefully i`ll have them all completed and functioning soon and actually get out into the field.
Time slips by with great speed this i do know.
cheers

 

[Bush]

The Dinner Plate Coil Top.
Plastic type seems a little brittle and difficult to work with.
The two separate packing protection angle fitment idea for the shaft attachment works well.
It will do for a while to test the new 2 layer 9 1/2 `` flat wound coil.

 

[grubstake]

The Dinner Plate Coil Top.
Plastic type seems a little brittle and difficult to work with.
The two separate packing protection angle fitment idea for the shaft attachment works well.
It will do for a while to test the new 2 layer 9 1/2 `` flat wound coil.

It'll be melamine, which is a thermosetting material (like bakelite), not a conventional thermoplastic. Be careful of dust and fumes when you're working with it:
https://en.wikipedia.org/wiki/Melamine