Chance PI coil...

[cabla33]

i have no housing yet, so i am still free to decide. (still planning to build my first MD)

i just wonder if the space between outer and inner wires is important as it effects total height and width of the coil.

let's say i build a coil with 8'' outer diameter and 6'' inner diameter and a slot-depth of 0.5'' then i would get a distance of 8''-6''-2*0.5''=1''

would be a wider (less height) or smaller value better for this distance or does it not matter?

[homefire]

Yes that would affect your number of layers. Just thickness if you use a bunch wound coil.

Forgo the Calculator if you want. Just use set know values.

Diameter of wire: 1 mm
Diameter of coil: 20 cm Frequency
Number of turns: 34
Parameters of coil: 1kHz 10kHz 100kHz
Inductance μH 523 520 515
Quality Factor Q 4.65 32 39
Capacitance nF/ μF 48.5 μF 486.5 nF 4.9 nF
Factor D 0.216 0.031 0.025
in Ω Rs 0.71 1 8.2
Resistance CC in Ω DCR 0.72 0.72 0.72
--
Diameter of wire: 1 mm
Diameter of coil: 20 cm Frequency
Number of turns: 30
Parameters of coil: 1kHz 10kHz 100kHz
Inductance μH 413 413 408
Quality Factor Q 4 30 40
Capacitance nF/ μF 61.4 μF 612 nF 6.2 nF
Factor D 0.25 0.031 0.024
in Ω Rs 0.64 0.82 6.3
Resistance CC in Ω DCR 0.68 0.68 0.68
---
Diameter of wire: 1 mm
Diameter of coil: 20 cm Frequency
Number of turns: 25
Parameters of coil: 1kHz 10kHz 100kHz
Inductance μH 291 290 286
Quality Factor Q 3.4 27 40
Capacitance nF/ μF 87 μF 870 nF 8.8 nF
Factor D 0.29 0.037 0.024
in Ω Rs 0.53 0.67 4.3
Resistance CC in Ω DCR 0.53 0.53 0.53
---
Diameter of wire: 1 mm
Diameter of coil: 20 cm Frequency
Number of turns: 20
Parameters of coil: 1kHz 10kHz 100kHz
Inductance μH 190 189 186
Quality Factor Q 2.5 22 40
Capacitance nF/ μF 133 μF 1.3 μF 13.6 nF
Factor D 0.38 0.045 0.024
in Ω Rs 0.46 0.54 2.8
Resistance CC in Ω DCR 0.46 0.46 0.46
---
Diameter of wire: 1 mm
Diameter of coil: 20 cm Frequency
Number of turns: 15
Parameters of coil: 1kHz 10kHz 100kHz
Inductance μH 110 109 108
Quality Factor Q 1.8 18 41
Capacitance nF/ μF 228 μF 2.3 μF 23.5 nF
Factor D 0.53 0.055 0.023
in Ω Rs 0.37 0.38 1.6
Resistance CC in Ω DCR 0.39 0.39

[baum7154]

i have no housing yet, so i am still free to decide. (still planning to build my first MD)

i just wonder if the space between outer and inner wires is important as it effects total height and width of the coil.

let's say i build a coil with 8'' outer diameter and 6'' inner diameter and a slot-depth of 0.5'' then i would get a distance of 8''-6''-2*0.5''=1''

would be a wider (less height) or smaller value better for this distance or does it not matter?

----------------------------------------------------------------

Hi Cabla33,

In my optimization of this coil it has been my experience that the self shielding nature of the coil begins to be diminished as the width of the coil form is spread. I believe this is due to the bigger holes or gaps in the outer windings that are tied to the ground end of the detector/coil system. This is why I don't use a form that is wider than 1.1". I think ideally the cross section of the coil bundle should be a circular form factor. If you take a look at my post #264 it lists my related posts for the RaceTrack version of this coil, and posts 30,31, 33, 34, & 35 of this same thread detail the construction of my 8" round coil. If you look at the 21.jpg photo attachment in Post 30 you will also see that the wires cross nearly perpendicular to the wire layers below and it is this minimization of parallelism that leads to lower capacitance along with the use of 600 volt or greater PTFE insulation for even greater inter-wire spacing. Coil capacitance is not our friend.
Note: Here in Colorado I don't need to use any additional shielding on this coil but in more highly mineralized locations the option to add more shielding is open although at the penalty of greater coil capacitance and hence slower coil speed/reduced sensitivity to small and fast targets.

I hope this helps,

Dan

[cabla33]

@homefire - thank you for your help!

@dan
yes, this helps and it confirms what i thought while reading this thread.
i will try to make the coil bundle as circular as possible while trying to minimize parallelism and using quality wires.
maybe i will try to build your interesting racetrack version later once i have more experience.

for now i think i have all info i need to start building the coil.

thank you guys!

[ionut_mtb]

i did not read all the thread but i have a question. is this coil suitable for wet sand/ underwater hunting? what material u use for support of the wire and what is the height of the coil. thanks

[baum7154]

i did not read all the thread but i have a question. is this coil suitable for wet sand/ underwater hunting? what material u use for support of the wire and what is the height of the coil. thanks

_________________________

Yes it is suitable for sand/water hunting. Properly constructed 3DSS coils are especially suited for small gold and allow detection of other fast targets as well as other large or slower targets such as rings. I do recommend that you take the time to read the posts. The form material I use is .093" polycarbonate or LEXAN. The height of the coil itself is about 22mm. I am sure that this measurement is mentioned in the posts of this thread.

Good luck,
Dan

[baum7154]

@homefire - thank you for your help!

@dan
yes, this helps and it confirms what i thought while reading this thread.
i will try to make the coil bundle as circular as possible while trying to minimize parallelism and using quality wires.
maybe i will try to build your interesting racetrack version later once i have more experience.

for now i think i have all info i need to start building the coil.

thank you guys!

-----------------------------------------------

Hi Cabla33,

A few more things on the 3DSS coil build. If you are trying to build a low capacitance fast coil and feed line I don't recommend using wire size larger than 0.5mm or 24AWG. This is because larger wire will have more wire to wire capacitance. Also I recommend using a continuation of the coil wire to form a twisted pair feed line that will have about 0.9 to 1pf of capacitance per inch. The feed line portion is twisted at a rate of about 3 turns in 25mm. The twisting is easily done with the free end of the wire pair chucked in an electric drill with the coil end pulled taught. I use heat shrink tubing to jacket the twisted line. For flexibility reasons I like the 24AWG 19 strand wire. This method eliminates solder joints in the coil that would be detected at short sample delays.

Dan

[ionut_mtb]

what about pvc coated wire? is good for this coil? need more turns to achive the right uH. (for ex i need coil for baracuda 1.5R 450uH original coil) what wire should i use for 10" or 8" COIL. did u experiment something like this?

[homefire]

Same Gauge wire as prescribed .

[Rinkerdink]

Reading through this thread I've lost myself down a few rabbit holes! Could anybody put me out of my misery and just tell me what coil to make for a mini pulse plus kit from silverdog? I was thinking of trying the Plantilla coil (from the first page of the thread) using 0.5mm enamelled copper. Before I lose myself in a tangle of copper wire can anybody tell me if this is likely to work or if i'd be better off trying something else (if something else please tell me lol).

Appreciate any help.

Cheers,

Chris

[baum7154]

[QUOTE=Rinkerdink;228101]Reading through this thread I've lost myself down a few rabbit holes! Could anybody put me out of my misery and just tell me what coil to make for a mini pulse plus kit from silverdog? I was thinking of trying the Plantilla coil (from the first page of the thread) using 0.5mm enamelled copper. Before I lose myself in a tangle of copper wire can anybody tell me if this is likely to work or if i'd be better off trying something else (if something else please tell me lol).

Appreciate any help.

---------------------------------------------------------------------
Please tell us what targets you will be seeking so we can better answer your question.

Dan

[baum7154]

If you will not be detecting very small gold at 6 us to 10us sample delays you will be fine using solid enameled wire on the narrower plantilla form. I doubt that the solid wire with enamel insulation will operate at sample delays below 12us depending on wire size and coil inductance. However for best performance on all targets,the use of thin stranded 600 volt 24awg or even Litz wire on the 1" wide wire form mentioned on every other page of this thread is recommended for fastest coil performance. Coil capacitance is the enemy of coil speed and to keep it minimized, inter-wire spacing using thick 600 volt or greater insulation and reasonably thin wire conductors is a must. The 0.5mm wire you mention is about 24awg. Eddy currents in solid wire will be greater than in stranded wire of the same gauge. Eddy currents are also the enemy of very short sample delays.

By the way the 'Plantilla' coil is a 3DSS coil and should exhibit self shielding properties. The solid wire of the Plantilla coil will not lend itself to use of it as the feed line and other likely types of feed line are big contributors of capacitance to the coil/feed system. You may minimize capacitance of your Plantilla coil with the layering of some thin closed cell polyethylene foam between the winding layers to give more spacing between the crossing wires.

Best of luck,

Dan

[ionut_mtb]

for bigger coil (10" plus) i should use same data like for 8"? (coil forms are 1" to 1.050", 37 slots 0.4", 1/8" slot) aiming only for coins and rings.

[baum7154]

Yes that will be very good for coins and rings.

Good luck,

Dan

[6666]

Hi baum7154, I was just looking at your post #23, were you useing just ordinary kitchen/cooking foil ?