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Old 21st February 2017, 01:09 AM   #21
DonVK is offline DonVK  Canada
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Very nice, ECO green reuse.

It's already "magnetics wire" which has insulation (varnish) so it can be repurposed. I'm assuming you're making an easy air bobbin style and not attempting a torroid. If I could get a supply of magnetics wire at reasonable price and qty I would wind my own as well.

You can parallel the strands, and resistance will decrease (like all parallel resistors) and current capacity will increase assuming you properly solder them at both ends. Do you actually need more capacity or lower resistance than 18awg? The effective capacitance increase will be minor because you have the same potential on both sides of the insulator (varnish) meaning no "E" field differential and no charge transfers. Its easy to determine the equivalent wire gauge via cross section area of 0.823mm^2 for a single 18awg so 2 of them is 1.65mm^2 or equivalent to a 15awg and so on https://en.wikipedia.org/wiki/American_wire_gauge.

Twisting is fine in moderation, but it does make the strands longer than the twisted pair length. You could also attach your bobbin to the drill and use it to wind the inductor as well. You can "guesstimate" the size of coil and it's resistance using manufacturers existing sizes (ID, OD, height, resistance) just look it up in the their tables. (http://solen.ca/wp-content/uploads/stdind.pdf) You could also use one of the many calculators, but I would still check it against an actual one.
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Old 21st February 2017, 02:10 AM   #22
jrh0516 is offline jrh0516  United States
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Winding calculator sites
Shavano Music Online - Cross-Over Network; Air Core Inductor Calculator
Pronine Electronics Design - Multilayer Air Core Inductor Calculator
An introduction to the air cored coil

I use an electric drill with a wooden axle to help wind. There are a number of plastic forms/ bobbins you can get from EBay. I’ve also made wooden forms
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Old 21st February 2017, 10:44 PM   #23
Butcher is offline Butcher  New Zealand
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"in that case, inductance will come mainly from amount of turns, and core diameter , while DC resistance will be directly proportional to wire length and inversely proportional to number of strands in parallel, which will dictate equivalent wire section."

Yes, thanks JMFahey. I may loosely wind three strands together for a start. Rt (total resistance should not increase too much. Loose winding will keep things a bit neater. All three strands will be equal length.


"But if you need to make stranded wire DO NOT US A DRILL it is not the way to go."

audiofan Thanks. I intent on using few twists as possible.


Thanks nigelwright7557. I am concerned about capacitance and its affect on sound. I guess at 500Hz and below, capacitance (inter winding) would me insignificant as far as Z goes (inductance).


"Hi Butcher, me again, I though you were in Australia, a mix up with the flags.'"

Careful our NZ airforce will send planes over !!!! Haha. Yes, I am in fact kiwi! (flag confusion, get your eyes checked digga!) hahaha. (Kiwi and Aussie joke. I am glad we kept our lovely flag. But lets keep to topic!)

"Heavens, they should just build a bridge between the two countries and be done with it."

Haha. What do you call a sophisticated Australian? A kiwi !!!! lol.


"Actually, non-inductive resistors generally provide very little benefit in passive crossovers because the audio frequencies are too low, any inductive reactance of a normal wire wound resistor likewise is essentially trivial at audio frequencies so making your own is likely to have inaudible results."

I measured a 1Ω (I think it was) wire would resistor and read about 1mH. that is quiet high. I am pretty sure the measurement was correct. The DC part should not matter. I might crack open the resistor and see how it is wound.

"If you were to make an iron cored inductor it is best not to use nails or ordinary iron parts as they tend to have high retentivity and poor permeability. Audio transformer cores are best suited for the purpose if you decide to make your own laminated iron core inductors. Just a few thoughts."

Yes, laminated iron to decrease eddy currents, if I am not mistaken. I suspect the laminates are dipped in enamel to form insulated layers (?). I don't care if the inductors are as big as oranges, space is no problem!

Thanks Tweet.


I have seen may formulas for estimating solenoid inductance. I would like to know roughly how large these inductors will be.

"If you need to calculate inductors look for '' weeler formula'' & '' brooks coil ''."

I will research this. Math is no problem for me as I studied electronics. Took me a while to get my head around math though (and lots of aspirin!).


So, air core it will be. I may parallel up three (or 4?) strands of 0.8mm wire at lengths of say 10M. then I will join together by solder. Then I can attach further lengths and measure total inductance. I can then fine tune them.

Any advice on what diameter to make the center? My 0.36uH ones use about 18 or 20mm. Can this be reduced to say, 5 - 10mm? This would make the larger (high inductance) inductors slightly smaller. I indend on securing these large inductors in home made bobbins with MS (silicon) and cable ties.


Also, can someone suggest rough dimensions of these inductors? (1.8mH and 3.6mH). I indent on using circular bobbins with height being 1/2 that of width.

Today I intend on doing some experimenting... Thanks for advice on using nichrome wire as resistors. I can obtain for free from old heaters etc. I might just use 3 or 5W metal film types from a store...



Thanks.
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Old 21st February 2017, 10:50 PM   #24
Butcher is offline Butcher  New Zealand
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"Very nice, ECO green reuse."

Thanks. Saves copper being melted and reused! Bad for our environment (and pocket!)

somewhere I have data on phase 1 to phase 6 fisher and paykel washing machine motor copper wire diameter. Data is on my PC somewhere. When I find it, I will share.

I suspect some use 1mm, or even 1.2mm wire (?)

Thanks DonVK and jrh0516 for the info!


More to come...
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Old 21st February 2017, 10:55 PM   #25
Butcher is offline Butcher  New Zealand
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Re Fisher and paykel washing machine motor copper wire diameter...

Series 60, 80 and 100 series stators...

60 series = 0.6mm
80 series = 0.8mm
100 series = 1mm


The early models (series 1?) uses the 1mm diameter wire. These machines were around in the early 90's and made in New Zealand.

So looks like the series 100 motors would be good candidate! I got a shite load of magnet wire from the 80 series motor. I do have some 100 series motors in storage at a mates place... I hope this info will help someone out. There is lots of info on creating windmill motors using these f&p washing machines... (see google).

Thanks.
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Old 22nd February 2017, 09:08 AM   #26
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by Butcher View Post
So, air core it will be. I may parallel up three (or 4?) strands of 0.8mm wire at lengths of say 10M. then I will join together by solder.
Neatness is important because the further a turn is from the core, the longer the wire used. It would be a shame to have your gauge compensating for this. I would suggest calculate the inductor and specifying an allowable resistance to see if you can do it with something you already have. If you have ever tried to wind one off inductors bifilar without twisting you'll know it may get difficult.
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Old 22nd February 2017, 09:12 AM   #27
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by Butcher View Post
I measured a 1Ω (I think it was) wire would resistor and read about 1mH. that is quiet high.
That would indeed be high.
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Old 22nd February 2017, 12:32 PM   #28
DonVK is offline DonVK  Canada
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The parasitic inductance and capacitance in wire wound resistors are quite low (<10R, uH, pF) and should not be a concern for audio frequencies. I've read a number of threads confirming this, unfortunately they are buried in other topics and I don't have them at hand. Look at it like this, if you could buy a $0.5 resistor and use it as a 1mH inductor it would be a bargin :-)

http://www.resistorguide.com/inductance/
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Old 22nd February 2017, 11:11 PM   #29
Butcher is offline Butcher  New Zealand
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Um yes, mine read about 0.8 - 0.9uH.

So not 1mH but 1uH! I was only 3 decimal places off!

I was reading resistors of approx 1Ω to about 4Ω7. So it looks like I will be using w/w resistors afterall. I have spaced them off of the PCB so as to allow them to not get too hot or resistance will increase.

I am using a 33Ω resistor as part of tweeter attenuator (simple potential divider circuit for -2dB). I will measure that resistor as I presume it will have more windings. I guess higher wattage resistors use thicker wire and possibly less windings (? probably not less windings though).

I intend on 'upgrading' to metal film resistors eventually. I guess w/w resistors are not as noisy as carbon composite types!


Today me and my friend will be making bobbins for the large inductors. I will share some photos of our creations soon (I guess you folk like pictures?!).



Thanks for your i/p Folks!

Last edited by Butcher; 22nd February 2017 at 11:15 PM.
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Old 22nd February 2017, 11:35 PM   #30
Tweet is offline Tweet  Australia
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Butcher, if you have some old, used, scrappy CD's or DVDs you might be able to use them as bobbin sides. A few of them per side would save you a bit of effort.

Just a passing thought.

C.M
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