[Lowfer] Hints-Toroid Winding

[Peter Barick]

Group,
Re: Hints on Winding Toroid Cores

Usually this topic generates some groans, and understandably: fingers too =
large, cores too tiny, wire too fine, a formula for frustration. Well not =
all the time. . . .

Recently I was making a few isolation x-frmrs as was mentioned on this =
list. The cores, FT 87-? J, are better to work with than the =BD inch =
types, but no. 28 - 30 wire is still a challenge to handle. Here's what I =
learned on winding duplex windings.

Fist get an idea off what x-turns means in a straight wire length. To do =
this, take a foot of the wire and test wind it on the core. How many turns =
were made? Use this value to extend out to the required turns plus 1 foot =
for leads. This gives a reasonable amount of wire to handle.

Label the core with its value on a piece of tape. Start winding. I held =
the two wires in parallel and started the wrapping. I quicky found that =
feeding the wire as if lacing a shoe produced kinks and tangles. Bad for =
frustration. Better to feed the wire by pushing a small loop into the =
core, then pulling the rest through. No kinks!

Spacing: Turns should not touch each other. This is very hard to achieve =
while winding. Better to lay them on close, then when turns completed and =
secured, spread them out uniformly, I used a small paring knife from the =
kitchen. I used an 1.8 inch strip of bandage tape to secure the start and =
end points. If the label is now covered up, make another with the type and =
turns count. Affix this to the intended equipment. Sounds dumb but try =
remembering this "important" fact in a few days. ;-}

Winding technique two: This is again for a two winding x-frmr. Separately =
wrap first winding using appropriate wire that has a plastic covering. =
Space the turns, leaving a gap between start and end turns. Next wrap reg. =
enameled wire between the first set. The spacing is controlled by the =
former windings and seems to go faster using the "push" method.

One of these is housed in a sardine can. It is centered and secured on a =
piece of pressed board. One connector is mounted in a hole on one end, the =
other conn. is on the other end but insulated from the can, as per good =
noise reduction practices. The can lid opens on one side only and a small =
tab secures it to the body to close up the "case." To make it water tight, =
a bead of silicone can be used.

Hope others are encouraged on winding toroids for uses such as this.

Peter