I need to wind a few coils by hand on RM12 formers - 3mH @ 2A DC chokes. I did one as neatly as I could, and found that there was quite a bit of spare room on the former, although my next size up of wire probably wouldn't fit.
It would be much quicker if I weren't neat. I suppose it would add a bit to the resistance and might even reduce the self capacitance, neither of which matter much.
Any good reason why I shouldn't just go for speed instead of neatness?
Cheers
-- Syd
On Wed, 2 Dec 2015 20:15:28 +0000, Syd Rumpo Gave us:
Depends on the turns count.
If only a single layer, the ideal wind is a space between each turn the same width as the wire gauge.
"Scatter wind" as it is called with a high turns count wind, introduces problems on transformers if the turns at the beginning of the winding get close to final turns and the count and V per turn is high enough to approach the insulation strength of the mag wire. It also introduces other parasitic effects but they are fairly minimal on miniature sized devices as I presume are those which we are discussing here.
On an inductor, scatter wind is not as problematic, but still has a few negative effects.
On a high turns count, small bobbin scenario, I usually wind one perfectly flat layer, and place a 1 mil transformer tape barrier between that one and the next layer as I step up onto it. The wire follows along no problem. I also do not wind to the full width extents of the bobbin. As in I keep a mm margin or the like at each edge and the tape locks that in place. This extra 'creepage' distance makes multi-layer, high turns count windings retain integrity under the voltage stress. Again, that typically only refers to transformer windings. But it doesn't hurt to follow most of the same practices when winding an inductor too.
So to conclude...
IF the turns count is low enough to allow it, evenly spaced turns maximize the way the flux gets distributed. The ideal spacing is one wire, and one wire width space.
I am making a high power antenna matching board where some of them are wound and locked onto large alumina tubes.. I drew up a mandrel for my winder that has evenly spaced grooves cut onto a delrin shaft, which I then remove and slide over the alumina tube before I lock the turns down with hard set epoxy.
We were also thinking about buying groove alumina tubes, but the prices for custom stuff is pretty expensive and would have to wait until after the dev phase. They also get locked into a specific wire gauge as well, whereas my mandrel solution relies on a set of mandrels made for specific gauges and diameters.
No good reason at all. Just keep your start and finish away from each other.
Thanks both. I went for it, wound 120 turns on 8 separate bobbins, and they all measure the same as far as I can tell or care.
Cheers
-- Syd
On Thu, 3 Dec 2015 22:25:29 +0000, Syd Rumpo Gave us:
The difference is minimal. Did you only measure inductance or get Q numbers as well?
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