How To -> Bifilar Coil Winding
How To Wind a Bifilar Coil
||Thursday 26 July 2007
||Thursday 26 July 2007
||This mini-project shows you how to
wind a bifilar (2 wire) coil. The 870 wind coil created using
the below procedure took approx 20
minutes using our manual coil winding jig.
||View the photos and video to see
how it's done.
||This demonstration uses the manual
coil winding jig as described in our mini project sheet
How To Build a Simple
Coil Winding Jig. The actual coil wound in this
demonstration was used in our project Bedini SSG Battery
In this "how-to" we are going to wind a bifilar coil for
our Bedini SSG Battery
Energiser project (however we shall not be placing the core material
in the coil for this example).
The empty black plastic spool was a freebie from my
local hardware store (the spool had link chain on it, which had been all
sold, so I asked if I could have the spool). The spool dimensions can be
The 2 spools of enameled copper wire was purchased from
1 x empty plastic spool, approx 90mm high with 70mm
to 90mm diameter flanges and a core hole 14mm to 20mm in diameter.
1 x spool of enameled copper wire, 0.5Kg, 0.56mm
(close to #23 AWG), approx 120m in length. RS Stock #357-750.
1 x spool of enameled copper wire, 0.5Kg, 0.80mm
(close to #20 AWG), approx 100m in length. RS Stock #357-772.
Black electrical insulation tape. A$2.00 for a pack
of 4 rolls.
View the completed (wound) coil here.
View the winding videos, either streamed (in a new
web browser window that opens automatically when you click on the link)
via the YouTube website, or via downloading the Microsoft wmv files to
Ensure you've got all the parts and equipment
you need (refer to the lists above) before starting.
View all the drawings, photos and videos (above) to
get an idea of what you're about to build. Print off any
drawings and photos to help with the construction process.
Set aside 30 minutes to complete your first wind (if
using the recommended manual coil winding jig) or 3 to 4 hours if
winding by hand. The remaining instructions apply to the manual
winding jig only.
Start by drilling 2 holes in the empty (coil) spool
- 1 in the top flange, and 1 in the bottom flange. The 2 holes
should be opposite one another. The holes need only be big enough to
fit the 2 copper wires through (we used a 2mm drill bit).
Stand (or sit) in front of the manual coil winding
jig, so that the cranking end is closest to you, and the copper wire
"feeder" end is furthest away from you. It might help to print off a
copy of the
and place on top of the base plate underneath the coil spool as a
winding reference guide.
Place the empty spool onto our winding jig (undo the
retaining screw on the "crank" or "winding" shaft, slide the shaft
out of the left leg, slide the empty spool on to the shaft, push the
shaft back through the left leg hold and reattach the retaining
Place the 2 copper wire spools (0.56mm and 0.80mm)
onto the feeder shaft. It does not matter which spool sits on the
left and which one sits on the right.
Grab hold of both copper wires from the feeder
spools and push them, both together, through the left hand flange
hole we drilled earlier. Pull the 2 copper wires through the 2mm
hole so that around 100mm (4 inches) of wire pokes through.
Now, with your right hand, slowly wind the crank
handle anti-clockwise (backwards) so the 2 copper wires slowly start
to wrap around the spool. The 2 copper wires will come in over the
top of the spool towards you and feed around and under. Use your
left hand to keep the 2 copper "feeder" wires together.
Keep a count of how many turns you are making with
the crank handle. When you get up to a count of "100", stop winding
and write "100" (or a single vertical stroke) on a piece of paper.
Then begin counting from "1" again.
After 10 to 20 winds, slide the copper wire on the
spool to the left, so they sit side-by-side and give you more room
to wind on more wire onto the spool.
The copper wire will "move to the right" as you wind
it on to the spool. For our example spool it took 50 winds to
totally fill the black spool shaft. At this point our feeder wire is
hard up against the right hand flange.
Keep winding, but now start a second layer of
copper, moving your hand slowly from right to left. Don't be too
concerned if your 2 feeder wires want to start "parting company" a
little as they wind on to the spool. This is natural, but do try
your best to keep them perfectly parallel to one another as you wind
them on to the spool. Keeping your left hand close to the spool will
ensure greater accuracy.
You'll find your "second layer" won't be the same
number of turns as your "first layer" - your second layer will
probably be a few shorter than the 1st layer. This is natural as
we're not robots with precision winding skills :)
When you back back to the left hand flange, you've
completed your "second layer" of windings. Keep going - head towards
the right hand flange again to complete your third layer.
Keep doing this back-and-forth layer-by-layer system
until you have completed all the turns you require. For example, the
Bedini SSG bifilar coil calls for around 850 turns.
When you've completed your winding, use a pair of
pliers or wire cutters to cut the 2 feeder wires around 100mm (4
inches) away from the coil (front) spool. Then feed these 2 wires
through the little hole in the right hand flange.
Now, to finish off your spool, grab your black
insulation tape and wind it around your front spool, covering the
copper wire as you go. Just one or two layers of tape is sufficient.
That's it - all done!!