Winding Toroids

My advice when winding single conductor toroid....from Mike Weir, VE3WDM
1. Most if not all the time you have more wire than you need so when told to cut a conductor to lets say 12 inches I give myself around 13-14 inches. A wise person told me "it's better to have and not need than to need and not have" 

2. If you are winding a toroid that has lets say 20 turns when you hit 19  I stop and count the turns just to make sure I am not at 20 or that I lost count and am only at 18!  I have had both happen.... it's better to check rather than cutting the excess wire and finding out you need to somehow add 2 more turns. 

3.Once the toroid is wound check the turns to see if they are more or less equally spaced. Take your time and move the windings around the core. Use a plastic tool or wooden tool for this a metal tool (screw driver) may remove the paint on the wire and cause a potential short.

4. Take the new toroid and see how it fits on the board. Sometimes you may have to squeeze the turns or open them up a bit for the toroid to fit properly. 

5. Once the turns are good and the fit is good you can trim off the extra wire. When I do this I always make on leg shorter than the other. I find you can place the toroid on the board with less effort by having the lead staggered in lenght. This is very evedent when you have a toroid with more than one winding..

6. Now that the toroid has the right amount of turns, it is spaced correctly, fits nicely and the leads are cut one longer than the other....its time to remove the enamel coating off the wire. There are some various
 ways to to this........ 
Getting ready for solder blob
A. Use a lighter to burn off the coating
B. Use sand paper.
C. The solder blob method.
D. Use a razor knife to scape the coating off.
E. I have heard some dipping the wire in var-sol....would not recommend it.  

I use the solder blob method and I have tried the sandpaper (find it just to rough for the delicate work that is needed) I have tried the lighter method but found on the smaller toroids I am not able to control the heat and end up burning off to much insulation. The razor blade scraping I have not tried and really don't want a razor knife that close to my fingers. SO....it's the solder blob for me!! I find if I put the toroid in an alligator clip to hold it I can in a very controlled fashion remove the right amount of enamel from the toroid.
I change the tip on my Weller soldering iron to a larger tip and use a .030 diameter solder. Most of my board work is done with a .020 diameter solder.

DO NOT SKIP STEP 7.....
7. Once the toroid wire has been stripped I use my DMM to check to make sure the coating has been removed and there is good continuity. Oh and for toroids that have more that one winding I check to make sure there is not shorts between the windings as well.

8. It's now time to solder the toroid in place and I find once the toroid is soldered in place before the leads are trimmed you can heat each solder blob up again and give each lead a LIGHT pull with a pair of pliers. This will allow the toroid to sit firmly on the board.

Some tips
1. Practice practice practice......it's like CW it's an art and over time you will get the idea and look forward to it.
2. Some toroids have nice rounded edges but be aware of those with sharp 90 degrees edges. These toroids can if your not careful remove the insulating coating from your wire and potentiality cause a short.

Using a paper and pencil to count
3. When  you have a toroid with 20 turns or more you can go buggy trying to check the turn count. What I do is lay the toroid on a sheet of paper and pencil make on the paper each turn. I then count the pencil marks and sometimes ticking them off as being counted.

4. Use two sizes of soldering tip's one (I use the Weller ETC 1/8 tip) for the solder blob used to melt the insulation off the wire. Then a thinner tip (I use the Weller ETR 1/16 tip) for soldering the toroid to the board.
ETR and ETC tips



Coming soon how to wind the bi-filar toroid and transformer toroid.


Mike Weir, VE3WDM, is a regular contributor to AmateurRadio.com and writes from Ontario, Canada. Contact him at ve3wdm@hotmail.com.