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Unwinding and rewinding transformers

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Myke

Sun Mar 18 2007, 04:18AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

I'm unwinding a trigger transformer from a disposable camera and the wire broke wih the wire I got off I'm tring to wind it on a ferrite core. I'm wondering how you keep the wire from breaking when unwinding it and how would you keep the wire from getting tangled? Also how would you remove the enamal from a piece of magnet wire that is around 36awg?

...

Sun Mar 18 2007, 05:04AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

1. remove it very carefully.
2. wind it into a large diameter spool (old paper towel tube might work)
3. take a hot soldering iron, put a nice fat glob of solder on the tip, run the wire through it. Sometimes it is easier to wrap the wire around something (lead of a resistor etc) and then solder it to the lead, and then once the insulation melts away pull the wire away, but with such small wire you run a decent risk of it breaking.

Myke

Sun Mar 18 2007, 02:57PM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

Thanks for the info.

How would you wind it onto a ferrite bead though because you have to pull all the wire thru the ferrite bead. Maybe you could use a sowing needle? The wire broke because it got stuck on some wax near the end and now i can't pull up the wire form the wax.

Electroholic

Sun Mar 18 2007, 04:31PM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

dip it in a cup of hot water, that should soften the wax enough.

benbradley

Tue Mar 20 2007, 04:08PM

Registered Member #312 Joined: Mon Mar 13 2006, 01:50AM
Location: Georgia, USA
Posts: 27

Are you unwinding the transformer to reuse the wire? If you can possibly afford it and wait for shipment, I strongly suggest buying new wire. About 1/4 pound of 36awg magnet wire should be only $5 to $15 or so.

I get insulation off magnet wire ends by pulling the end through fine (400 grit or smaller) sandpaper. Fold over the sandpaper so the grit sides face each other, put the wire end in and hold lightly between finger and thumb while pulling it out. That gets 'top and bottom' - turn the wire 90 degrees and repeat. The bare copper is usually shiny and clearly a different color than the coating. Solder it within a short while (maybe minutes or hours after stripping) so the exposed copper doesn't get an oxide coating that makes it harder to solder.

Steve Conner

Tue Mar 20 2007, 04:55PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Yes, salvaged wire often has the insulation damaged. I like to strip thick magnet wire by scraping the enamel off with a penknife, the thin stuff with sandpaper, and the really thin stuff by burning it off with a soldering iron set as hot as it will go.

Marko

Wed Mar 21 2007, 12:03AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Yes, wire from transformers wich have been varnished or epoxy-ed will usually tend to strip it's insulation off.

Anyway, I don't see what is so special about the tiny trigger transformer? If you need really thin wire, 0,1 and 0.05mm and etc, pretty good sources are mains voltage relays, telephone relays, shaded pole motors, various mains- powered solenoids, alarm clock coils, etc, and those all are usually unvarnished and easy to unwind without damaging the wire.

Mains transformers are also good if unvarnished, but you usually need to saw the core off.

ShawnLG

Wed Mar 21 2007, 04:03AM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

I assume you are trying to replicate my small joule thief. The wire from the trigger transformer will not work. The wax on the wire is sticky and will make threading the bead impossible. Another thing to keep in mind is that the smaller the joule thief transformer is, the more turns you will need to make it work. The wire that I used is from a rare high impedance db meter. I suggest looking in battery operated analog clocks, analog watches or magnetic reed switches.

CT2

Wed Mar 21 2007, 04:24AM

Registered Member #180 Joined: Thu Feb 16 2006, 02:12AM
Location: Ontario, Canada
Posts: 187

Why not unwind the wire from the transormer that charges the cap (in the disposable camera, its the bigger of the two). I've unwound those pretty easily with no problems, and that wire is very thin.

Firnagzen

Wed Mar 21 2007, 10:26AM

Registered Member #567 Joined: Tue Mar 06 2007, 10:55AM
Location: Singapore
Posts: 147

If you ask me, by far the easiest is a cheap clock! If you open one up, there's usually a coil of really thin wire inside as part of the motor. And the best part is, it always comes on a nice little spool which is easy to store.

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