spiral pi coil

[green]

Couple tests with spiral and bundle coil reply #26. Some thoughts, maybe correct maybe not. Spiral coil is best wound with zero spacing between wraps. (1.5 inch foil target)bundle coil has higher signal at same delay time because of higher inductance for same number of turns. Spiral coil has higher circuit resonance allowing less delay, higher signal if sampled sooner. Bundle wound with Teflon coating wound have higher circuit resonance, thicker insulation calculates inductance similar to spiral coil. Thinking magnet wire spiral coil would be similar to Teflon bundle coil. (copper plate target)shows increase in needed delay if MUR460 is eliminated, less than 5us with and little over 10us without. Signal same with and without MUR460 because Tx current is in a control loop(160us, constant rate, 1A peak). Two stage amplifier, gain of 15/stage for total of 225. Still wondering why professional coil might be better? Spice simulation seems to be similar to comparison test.

Used 1inch foil target(TC=1.5us) instead of 16mm square foil(TC=1us)spice model to get a higher signal for testing. Square target cut from regular strength aluminum foil(.063us TC/mm)*number of layers. About 16mm for 1us target. Square target cut from aluminum coke can side(.225us TC/mm). About 4.5mm for 1us target.

[green]

I am not spice savvey but Im wondering can you change the inductance of the spiral both higher and lower to see if the 1 tc target improves.
Thinking 200 uh might be a good value for a dd Rx.
Thanks Agian.

Haven't replied because not sure my spice model is correct. Guessing changing DD Rx from 300uH t0 200uH wouldn't improve signal strength unless could sample sooner. 1us target looses 90% of signal every 2.3us, sampling 1us sooner would help.

[dbanner]

An attempt at comparing a bundle wound coil vs a spiral wound coil I have with spice. Added 50pf to coil capacitance for lead wire. First compared coils as wound, bundle coil has higher inductance but less current. Second changed bundle coil to 23turns for same inductance as spiral coil. Higher current because of lower resistance. Don't see much difference with nickel or quarter. SRF higher than expected with the bundle coil so simulated with D1 shorted and not shorted. Spiral coil seems to be better with nugget with 1us TC. Wondering if I'm missing something with my simulation?

Edited, I'm guessing that the spiral coil should perform better than the bundle coil at higher PRF.

[godigit1]

When you log in, click on the "Remember Me" box.

Hi Qiaozhi
Ive Have been trying that.
I have to keep two tabs open and switch to the other tab make sure Im logged in and then I can post.
I changed my passwords and today at least i was able to post.
Im thinking it is a security setting on my computer thats doing it. I keep changing setting but noting Ive found has totally fixed it yet.
So far today I have not been droped but Ive kept the other tab open just in case. When I go to the other tab Im still logged in so maybe Its fixed .
Thanks for your Reply.

[godigit1]

An attempt at comparing a bundle wound coil vs a spiral wound coil I have with spice. Added 50pf to coil capacitance for lead wire. First compared coils as wound, bundle coil has higher inductance but less current. Second changed bundle coil to 23turns for same inductance as spiral coil. Higher current because of lower resistance. Don't see much difference with nickel or quarter. SRF higher than expected with the bundle coil so simulated with D1 shorted and not shorted. Spiral coil seems to be better with nugget with 1us TC. Wondering if I'm missing something with my simulation?

I am not spice savvey but Im wondering can you change the inductance of the spiral both higher and lower to see if the 1 tc target improves.
Thinking 200 uh might be a good value for a dd Rx.
Thanks Agian.

[Qiaozhi]

I keep loosing my posts ,Im having a computer or forum problem I cant fix so i have to Type fast or I get signed out.

When you log in, click on the "Remember Me" box.

[godigit1]

Hi Green,
Sorry about your tester.
I keep loosing my posts ,Im having a computer or forum problem I cant fix so i have to Type fast or I get signed out.
Thanks again for testing those coils.
You are right about the pro coils I need to revisit them and properly test them . All these coils are shielded and really good coils in my opinion, Whites coiltek Digger john jimmy sierra coils. Thant being said its no suprise I have not made a better coil as of yet.
Im was mainly comparing by target performance.
My low tc targets were the 1/4 square of cola can and a 1.2 gram nugget.
As far as retesting the coils I think you nailed it the first time.
Coils 2 and 4 are a pretty good wash as far as performance to size I think.
Coil 3 is way off the make as far as inductance I wonder if I made that one properly if it would do better.
Its the same stack as the others just flat instead of verticle.

[green]

An attempt at comparing a bundle wound coil vs a spiral wound coil I have with spice. Added 50pf to coil capacitance for lead wire. First compared coils as wound, bundle coil has higher inductance but less current. Second changed bundle coil to 23turns for same inductance as spiral coil. Higher current because of lower resistance. Don't see much difference with nickel or quarter. SRF higher than expected with the bundle coil so simulated with D1 shorted and not shorted. Spiral coil seems to be better with nugget with 1us TC. Wondering if I'm missing something with my simulation?

[green]

P.s
To actually answer your question. I use all profesional coils on my detectors.
Ive been able to make nothing that will beat them yet. Ive had some pretty good ones but no winners. On my kt315 1st edition baracuda the yellow coil you tested was very good.
I now think that it was a accidental match to that detector ,got something right.
Also this is off topic a bit but that baracuda is really partial to the type of diode used.
That coil with a high intensity green led performed right up there depth wise with my MPP and a 12 inch dual field. Ive yet to remake it but have been saving that spool of wire.

Wondering if the reason the professional coil is better is measurable. Have you compared diameter, inductance, resistance and SRF with your coils? Maybe some other measurements? Another possibility, professional coil has less noise for some reason? Are you testing with a short or long TC target? Test I did awhile back with some of the coils you sent me. Your coil is better at close distances than my spiral coil, smaller diameter is some of it. Still looks like your winding might be a little better for some reason. Zapped my test circuit with integrator awhile back or I would try testing again to see if I missed something.

[WM6]

Do you see any differance in recovery time between copper and aluminum on coils of the same inductance?

.

No significant, if we are trying to retain genuine copper coil specification.
To achieve this, due to higher Alu wire resistance. I am using multitread ECCA wire composition, spiral twisted
to get some sort of Litz wire with approximatelly equal wire resistance to comparable copper wire.

[godigit1]

Thank you WM6,

Do you see any differance in recovery time between copper and aluminum on coils of the same inductance?
Cost appears to be a benefit as well.
Ive been trying to justify buying some rectangular magnet wire for experimentation but its super hard to find in small quantities and expensive.

[WM6]

Hi WM6
What benefits have you found from aluminum vs copper other than the obvious price?

Weight of coil in first line.

As others mentioned soldering could be a little tricky.

Despite ECCA wire is not bare aluminium wire, but copper plated (CC- copper clad), soldering is not equal to pure copper wire.

Soldering shoud be performed as quick as possible. This way usual 30W soldering iron is here (in case of 0.5mm PI wire) no go.

With week soldering iron it takes to long to heat soldering joint (and melt lacquer), which in result oxidise instead to make proper
solder joint.

Soldering iron should be at least 80W, finally heated, with enough melted solder on it and soldering joint of say two ECCA
wire sould be prior pured with quality (IC) soldering paste. This way assure that soldering time is no more than second.
If possible, due construction limits, put (sinking) soldering joint in soldering bad for second is even better.

ECCA wire final lacquer should NOT be sanded off from soldering contact parts of wire before soldering (as we do with pure copper
Cul wire). Sanding lacquer off, will sand off tinny copper clad too and bare Alu wire is hard to solder (possible only with special Alu
solder paste - available on eBay too).

[Qiaozhi]

White's used to make the 950 coils with aluminum wire on the TX side, primarily to save weight. But it was problematic to make electrical contact with and coils would sometimes go bad over time, so they switched back to copper. Copper-clad aluminum would solve the contact problem.

Garrett also used to make their large 12" Crossfire coil with aluminum wire on the TX side. Again, this was a point of failure where it was soldered to the copper wire of the nulling coil. I've repaired a couple of these with aluminum solder, but the shell is an absolute pig to get apart. I had to glue a coil cover over the repaired area to hide the damage.

[Carl-NC]

i don't think steel would work but alu magnet wire might just, so what do you guys think?

White's used to make the 950 coils with aluminum wire on the TX side, primarily to save weight. But it was problematic to make electrical contact with and coils would sometimes go bad over time, so they switched back to copper. Copper-clad aluminum would solve the contact problem.

[godigit1]

From about 5 years ago I am using almost only "Alu magnet wire" for coils.

More specific so called ECCA (Enameled Copper Clad Aluminum) wire. From China - of course.

Hi WM6
What benefits have you found from aluminum vs copper other than the obvious price?