Different way to wind inductors?

[apassgear]

Have also used the PVC tube idea mentioned by Ashok. In this case I start with a cut to length tube as mandrel and leave it with the coil. The tube is cut in a lathe for squareness.

 

[Shaun]

Low-cost diy LCR meter

You can download Speaker Workshop for free http://www.speakerworkshop.com.

Apart from being a great bargain, it allows measurement of passive components using your PC/soundcard and simple test jig.

I like to promote this program among fellow diyers, because it's free, can do acoustic measurements, measure impedance curves, simulate crossovers and measure passive components within a (useful) limited range. It's not as sophisticated as proprietary software, but it works.

FYI- I've now bought SoundEasy, which is more sophisticated, and can do all of the above plus more.

Oh- and I also use the Shavano software for making coils, together with the scrape method. Just calculate for 110% of desired inductance and then unroll until you get the wanted value. Copper wasteage is low (certainly not 10%!), and accuracy improves with experience (+10% is just a rule of thumb).

For bobbins I use particle-board (chip-board) cutouts made with a hole cutter drill attachment, with cutouts from tweeter holes bolted to both ends. Use a brass bolt ( or other non-ferrous metal) to avoid affecting the inductance. The endcaps are re-useable.

Regards

 

[chris ma]

Re: Re: Need help designing the top

Chris, I hope your not thinking of winding the coil over the pipe.


Assuming you will be making an air core inductor:
What I would do with the setup you show is to build a smoth cylindrical but somewhat conical core were you will build the winding. Most likely a machine turned piece made of hard wood or metal with a cental hole to pass the shaft, you don't need a 1" dia. shaft for that, maybe a 1/2" solid will do.

The other thing to solve is how you will attach the side plates for containing the winding. A simple solution would be to put a couple of srews to hold them to the core mandrel. The other way would be (somewhat more costly or complicated to build) to have the shaft with thread on the area of the mandrel and add two nuts to press the plates against the mandrel.

Care should be given to size the coil in relation to the wire cross section this will help to keep the coil from deforming when you take out the plates and core. You can help to retain the build by adding adesive tape every two or five layers around the coil.

One last thing you may want to consider is adding a crank to the shaft.

Hi Tony,

Yes, it is going to be air coil for power supply Pi-filter. Recently I followed a link to a site where I can provide the inductance value and it displayed a chart with different core/hole size and width of the air coil and number of turns and the length required for a corresponding awg size wire.

I have at hand a smaller roll of awg12 and a large roll of awg14. If I were to make the same 2.2mH air coils, the chart says I need to have a 4.75inch diameter core with 1.25inches width using awg12 and a different one for awg14 I do not remember the exact value for now, that means I will have to make two mandrels; can I just make one mandrel and use my LCR meter to make sure both guage size air coils have the same 2.2mH and get away with it? Or do I have to follow the chart?

Thanks,
Chris

 

[chris ma]

Do air coils have to be circular or round? Can I make a square air coil, I think it is easier to make the square form to roll onto rather than a round form.

Chris

 

[JOE DIRT®]

Chris you can make it square also

 

[chris ma]

Thanks,
But I went ahead and bought a rotary tool from crappy tire anyway. I used ¾” mdf boards to create the mandrel. The mandrel looks like this with detachable options.
8” diameter ----------------------
5” diameter ---------
5” diameter ---------
8” diameter ----------------------

I used a ½” threaded rod as axel with a handle attached to one end.
After a whole weekend with 3 broken bits and 4 burnt bits the mandrel finally finished.

Now that I have created 4 air coils using 14awg magnet wire. I am wondering that can I use them in the Pi-filter for PSU even though they do not have identical values or should I continue to cut the wire to make them all the same?

No.1 has 2.88mH with 0.49ohm resistance.
No.2 has 2.95mH with 0.48ohm resistance.
No.3 has 3.11mH with 0.50ohm resistance.
No.4 has 2.90mH with 0.50ohm resistance.

The transformer is a 22-0-22 400VA will be in CLC format, the amp will be drawing a constant 4A class A. using 2 rectifier bridges with +Ve ,0 and -Ve , 0; L1 and L2 will be on +Ve and –Ve. Repeat this for the second PSU. The rail voltage will be whatever left over after CLC and may be a couple of breeder resistors.

Please warn me of any potential problem I may encounter.

Regards
Chris

PS: Is it true to say that there is only 2A going thru each air coil in this formation?

 

[JOE DIRT®]

Chris most coils have a +/- 10% factor....your coils will be fine to use.

when you get into RF design thats when the coil becomes critical and the spacing between the wire but for audio even a "scramble wound" coil will suffice in MOST cases.

DIRT®

 

[apassgear]

Re: Re: Re: Need help designing the top

Hi Tony,

Yes, it is going to be air coil for power supply Pi-filter. Recently I followed a link to a site where I can provide the inductance value and it displayed a chart with different core/hole size and width of the air coil and number of turns and the length required for a corresponding awg size wire.

I have at hand a smaller roll of awg12 and a large roll of awg14. If I were to make the same 2.2mH air coils, the chart says I need to have a 4.75inch diameter core with 1.25inches width using awg12 and a different one for awg14 I do not remember the exact value for now, that means I will have to make two mandrels; can I just make one mandrel and use my LCR meter to make sure both guage size air coils have the same 2.2mH and get away with it? Or do I have to follow the chart?

Sorry for the delay,

You can use any form you desire as long it is congruent with the wire size. This means don't use a 1/2" mandreal for winding a 12 Ga. wire. If values are simillar use the same mandrel. Width of 1.25" for a 4.75" dia mandrel seems narrow for my taste. For a 2.2 mH on either wire size I would start with a mandrel of only 2 or 2 1/2" dia with 1.5" or 1.75 width.

On this type of inductors I prefer to use round mandrels since it's easier to build and you can rewind inductors using the same wire. On square mandrels you will never get rid of the breakes of corners on the wire, so the wire will be useless if you don't like what you did.

And yes, you may add or take turns to get the desiered inductance.

A further comment. Not recomended, but I also some times add wire to an inductor by means of a solder joint making a hook on both ends of wire and then tighting them with a plier before soldering. Use one turn of mylar tape around the solder joint. Use a high power solder iron for these big wires. It works.

 

[flyingtele]

Just a note, to anybody interested check ebay for LCR meters, I bought one for about $20 brand new including international shipping. Its accurate too, compared it to a fluke and was within 0.002 mH or so, also measures capacitance and resistance, and has a transistor hfe tester. I only bought it for measuring inductors I make, but it has turned out to be much more useful and an absolute bargain (had to replace the probes though as they were junk haha)

Sorry, didn't mean to drag up such an old thread, only saw the date of the last post after posting

 

[mondogenerator]

the best way i have found is to tread an M8 screw thru any bobbin you wish to use, using a cordless drill wind the coil. Always overwind by 10 percent, trim to tolerance. Then varnish. Fix with epoxy or silicone. Never use brass screws, or ferric either, ALL will affect inductance. Most coils i have made, i bought a few but its easy enough if you follow simple rules, and use the correct wire gauge.

 

[kipman725]

My method of winding audio inductors is possibly the cheapest and easiest and still yields decent inductors:

1. make winder out of cd-r cake box with a removable pin through the top of the spindle.

2. Random wind copper magnet wire onto the spindle occasionally sanding a section off the measure the inductance using a cheap ebay inductance meter.

3. When desired inductance reached slide off the spindle taking care not to disrupt shape.

4. Hot glue the coil till fully immobile.

5. Wire into circuit.