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Detector Technology and Electronics and new detectors => Detector Coils => Topic started by: Doug on Sunday September 20 2015 16:18:47 AEST PM



Title: Spiral wound coils?
Post by: Doug on Sunday September 20 2015 16:18:47 AEST PM
Spiral wound coils.
Has anyone wound a spiral wound coil? What are the pro's and cons for such coils for Pi's?
doug ::419::


Title: Re: Spiral wound coils?
Post by: WM6 on Sunday September 20 2015 20:34:35 AEST PM
Good smaller dimensions universal PI coil say till 11".
Excellent if you ask for low parasitic coil inner capacitance.
Not very sensitive due low Q.


Title: Re: Spiral wound coils?
Post by: Doug on Wednesday September 23 2015 10:11:05 AEST AM
  
Good smaller dimensions universal PI coil say till 11".
Excellent if you ask for low parasitic coil inner capacitance.
Not very sensitive due low Q.

I wonder if any of the new coils from NF or CT are spiral wound or perhaps some other winding configuration eg flat wound?
doug ::419::


Title: Re: Spiral wound coils?
Post by: techo_bob on Wednesday September 23 2015 11:36:26 AEST AM
Hi Doug

from the information available these coils are rectangular section litz wire, spiral wound in a compact form
allowing for slightly more turns for the same inductance.

Bob..


Title: Re: Spiral wound coils?
Post by: Doug on Wednesday September 23 2015 12:10:40 AEST PM
  
Hi Doug

from the information available these coils are rectangular section litz wire, spiral wound in a compact form
allowing for slightly more turns for the same inductance.

Bob..

Thanks. Might this account for the reported improved sensitivity (higher field strength?) of these new coils to smaller gold?
doug ::419::


Title: Re: Spiral wound coils?
Post by: Blacksand on Wednesday September 23 2015 13:06:03 AEST PM
Hi all,
I'm having good success with this coil on my new gpx4500. On very small targets, I have observed that the most sensitive point on this coil is approx. 2.5 inchs inwards from the edge of the coil, as with a standard mono coil which is close to the edge. I believe that it is a dual field coil as it gives you a double signal on very small targets when you swipe it outwards to the edge of the coil.


Title: Re: Spiral wound coils?
Post by: Doug on Wednesday September 23 2015 13:46:28 AEST PM
  
Hi all,
I'm having good success with this coil on my new gpx4500. On very small targets, I have observed that the most sensitive point on this coil is approx. 2.5 inchs inwards from the edge of the coil, as with a standard mono coil which is close to the edge. I believe that it is a dual field coil as it gives you a double signal on very small targets when you swipe it outwards to the edge of the coil.

What coil are you using,NF or CT?
doug ::419::


Title: Re: Spiral wound coils?
Post by: Blacksand on Wednesday September 23 2015 18:41:27 AEST PM
Hi Doug,
Coiltek mono elite.

Martin


Title: Re: Spiral wound coils?
Post by: GARY on Monday September 28 2015 19:34:21 AEST PM
I noticed a couple pics on the Geotech site showing what the poster said was his Scramble wound coil and the other his Flat wound Radial Coil.

Knowing very little on how coils are wound I assume the Scramble wound is another word for a Bundle wound coil which I think is the normal way a Mono coil is wound?

Also not sure if the Flat wound Radial coil is the same as a Spiral wound coil?

Gary..


Title: Re: Spiral wound coils?
Post by: greylourie on Monday September 28 2015 23:26:27 AEST PM
I vaguely recall authere describing something to aziz once, think over on Geotech. That might have been a bit like a spiral wound effort ?
Wheres authere ?


Title: Re: Spiral wound coils?
Post by: Doug on Tuesday September 29 2015 09:10:28 AEST AM
  
I vaguely recall authere describing something to aziz once, think over on Geotech. That might have been a bit like a spiral wound effort ?
Wheres authere ?
I am not sure but i think someone did some tests some time ago with a small spiral wound PCB coil?
doug ::419::


Title: Re: Spiral wound coils?
Post by: authere on Tuesday September 29 2015 10:25:55 AEST AM
Hi All,

GL, that brought back memories, I did wind a coil that was spirally wound but way different than what is being talked about

The cross section of my coil bundle was circular and hollow, the first wire at 12o'c the next at 3o'c and then 6,9 etc

The second winding around went alongside the first wire at 12,3,6,9o'c etc

The third along side the two already there etc

 A normal coil bundle gets its inductance from the close proximity of each wire in the coil bundle, whereas my coil was inducing the adjacent wire because of the winding technique

A normal coil bundle would have been wound with the inside row first and the outside last, this would mean the current flowing thru the coil would travel from inside to the outside, whereas my coil the current would have to travel  around the coil bundle several times before reaching the end of the windings

What I found with this coil is that it didn't need shielding, I could stand underneath power lines and it was dead quiet and still detected gold nugg's

I should have experimented with that coil longer as it did have potential, I stripped a 14" coil for the wire and wound it around a plastic conduit bent to shape and stuck the wire on with a hot melt glue gun

Cheers, Ron


Title: Re: Spiral wound coils?
Post by: 6666 on Tuesday March 15 2016 21:37:06 AEDT PM
Ron thats an interesting post, is your description something like my drawing ?
thanks
6666


Title: Re: Spiral wound coils?
Post by: WM6 on Wednesday March 16 2016 04:26:46 AEDT AM
Probably like this one of mine designs:

(http://i65.tinypic.com/21j26iu.jpg)

(http://i67.tinypic.com/24mydsi.jpg)

(http://i66.tinypic.com/2ezl1ck.jpg)



Title: Re: Spiral wound coils?
Post by: authere on Wednesday March 16 2016 10:46:47 AEDT AM
Hi 6666,

Spot on 6666, the first wire was laid down at 12o'c the second at about 4 wire widths around and the 3rd would of been about 3o'c

subsequent wires were laid until I got back to the 12o'c position then they were laid alongside each of the first pass wires , right around to the 12o'c position again

keep going until all the spaces are full, so that circumference of the conduit is completely covered with a single layer

although each wire is touching another wire the current does not pass thru the coil in that manner, it jumps or misses, it actually travels in a clockwise direction around the diameter but hitting only every 3rd or 4th wire depending on how many passes it took to fill in the gaps to completely cover the circumference in a layer of wire

so, ...one complete surge of current that  travels thru the coil would complete if from end to end of wire was say 25 turns of wire which is normally our coil bundle   ..would normally travel once around the circumference of the conduit if laid as in your drawing but it travels around the circumference 3or4 times depending on how many passes it took to fill in the gaps

so,...25 turns around the coil and 3to4 times around the circumference and magically the whole coil lights up even though no wire is touching the last wire to have current in it,....each wire (turn of coil bundle) has a gap of 3to 4 wires between it

I've read some books and inductance of a given wire has a given distance from the actual wire which can induce a current in an adjacent wire but in this case its thrown out the window because the adjacent wire is out of sequence BUT the whole coil still lights up and the coil can be used directly under a power line

 more testing needed to be done but normal distances were achieved with this design

Ron


Title: Re: Spiral wound coils?
Post by: 6666 on Wednesday March 16 2016 21:51:30 AEDT PM
Hi WM6

what is the wire on the outside of your coil, is it a shield wire , how well does it work with ground response.


Title: Re: Spiral wound coils?
Post by: 6666 on Wednesday March 16 2016 22:02:38 AEDT PM
Hi Ron
Thanks reply, interesting concept you have with that design, it would be a challenge to design a former for that type of wind on a 3d printer, do you remember how it performed with targets in the ground ?


Title: Re: Spiral wound coils?
Post by: WM6 on Thursday March 17 2016 06:04:34 AEDT AM
  
Hi WM6
what is the wire on the outside of your coil, is it a shield wire , how well does it work with ground response.

HI 4^6

It is two way wound coil.

Middle or core sector is  Zig-Zag/bundle wound and fixed with string plus epoxy to get sturdy circle along with (Japanese chopstick) bracket.
Outer sector of coil is alternate spiral wound, with hoping to act as self shielding coil at the same time with lovering inner capacitance.

Not tested yet.
I am out of two pin connectors and awaiting new connectors shipping from China this days.


Title: Re: Spiral wound coils?
Post by: 6666 on Sunday March 20 2016 11:11:21 AEDT AM
Hi WM6

just recently I was reading a thread on another forum somewhere did not keep the link but somebody there made a coil with not enough inductance so they wound a spiral wrap on the outside to see if that worked, at the time it was untested .


Title: Re: Spiral wound coils?
Post by: authere on Sunday March 20 2016 14:08:42 AEDT PM
Hi 6666,

That wouldn't work as the two electromotive forces would have a tendency to cancel each other out

Just like magnets they are more powerful one way than the other, the largest flat surface has the most pull

By winding a circle one way then counter winding in the opposing plane just won't work to their advantage

Cheers, Ron


Title: Re: Spiral wound coils?
Post by: IBGold on Sunday March 20 2016 16:41:17 AEDT PM
OK just to put something into the mix below is my latest spiral wound coil the idea came from Bugwhiskers and on preliminary testing is great but yet to test it on the goldfields I today finished putting it into a housing so will be testing it in the field in two or three weeks put here so the design is copyright.

Regards, Ian. ::62::


Title: Re: Spiral wound coils?
Post by: 6666 on Sunday March 20 2016 20:25:50 AEDT PM
  
Hi 6666,

That wouldn't work as the two electromotive forces would have a tendency to cancel each other out

Just like magnets they are more powerful one way than the other, the largest flat surface has the most pull

By winding a circle one way then counter winding in the opposing plane just won't work to their advantage

Cheers, Ron

Yes you would imagine that the 2 winds would produce odd lines of force.


Title: Re: Spiral wound coils?
Post by: 6666 on Sunday March 20 2016 20:28:27 AEDT PM
  
OK just to put something into the mix below is my latest spiral wound coil the idea came from Bugwhiskers and on preliminary testing is great but yet to test it on the goldfields I today finished putting it into a housing so will be testing it in the field in two or three weeks put here so the design is copyright.

Regards, Ian. ::62::

Thanks for the picture, it sort of looks 3d, is it a stacked winding ?


Title: Re: Spiral wound coils?
Post by: WM6 on Monday March 21 2016 05:24:17 AEDT AM
Hi Ron

Agree, if two winding's  are counter wound.

In case that both winding's are wound in same direction (no matter if one is plain wound and another one as spiral over first one) effect will be added no subtracted.

I am only not sure about self-shielding properties of such solution. Will try.


Title: Re: Spiral wound coils?
Post by: authere on Monday March 21 2016 11:14:32 AEDT AM
Hi Bugsy, Ian,

Well, that stopped me in my tracks, spiral wound with the shape of a wing profile and shielding built into the mould underneath with fine wire

Don't see the reason for doing that, but if it works who cares....good job Ian

The new Elite camo's from Coiltek which I own have a lot of extra weight in them or at least the 14" coil does, I don't see where it comes from

Cheers, Ron


Title: Re: Spiral wound coils?
Post by: techo_bob on Monday March 21 2016 14:21:29 AEDT PM
Hi Ron

I believe the extra weight would be, the extra No of turns required to get the same (correct inductance)
of the coil. being spiral wound.. This also contributes to the added sensitivity of this design.

Bob..


Title: Re: Spiral wound coils?
Post by: IBGold on Monday March 21 2016 16:27:37 AEDT PM
Hi Ron,

The shape is the shape of the mouth of a trumpet so we call it a trumpet coil it is spiral wound with both vertical and horizontal surfaces to the windings this one has even windings on both planes and no foam formers just air between the coil and the shielding which is on the internal surfaces of the housing self resonance completed is 770 KHz this one is using bifilar wound coil wire  but I need to find something better as it  has too much capacitance any ideas Techno Bob self resonance with out the cable is 1260 KHz and the housing/shielding only makes a 15KHz difference .

Ron what you are seeing is the bottom of the coil those wires are the coil the old Woody's wire 32/.2 tinned wire it was all I had left.

Regards, Ian. ::62::