Transformer winding question

[lokeycmos]

i need to hand wind a toroidal transformer for a project im putting together. the schematic is here:



https://www.maximintegrated.com/app-notes/index.mvp/id/1923



im using 24g magnet wire. the toroid is rather on the small side. i attached a pic. it is 1/8 in thick. and OD is .230 In.This is the core that is recommended in the text. what is the best way to wind this? should i evenly space the primary of 48 turns with CTthen wrap the secondary on top evenly spaced?. or should i do a bifilar wrap? the only problem with bifilar is that the primary and secondary are different lengths. please give me your input!

 

[dr pepper]

I'd be inclined to wind the primary and seconday on opposite sides, primarily for insulation, lightning strikes near phone lines can make some nasty spikes so you need good insulation, your schematic mentiones a 'safety barrier'

You also depending on design might get away with a larger ferrite, but if thats what you got better wind it under a magnifier/light.

 

[ronsimpson]

If the windings are on opposite sides of the core the isolation is good but the coupling is not. If you are trying to move power you want good coupling.
How much isolation do you need?
I have had magnet wire hold to 1kv, it should not be used that way. If you 2KV I know of better wire.

To get max power and min noise I would, start at the CT point and wind bifilar. Example: wind 10, then two more turns on the primary.
Example: wind primary 2T, wind bifilar 10T, pull out the CT, wind bifilar 10T, wind primary 2T. This keeps the AC losses and noise down.
On the other hand I often run supplies at 10x this frequency and fight AC losses.

Go ahead and wind any way you want for the first try. It will work.

I don't know what core you are using and if that will work!

 

[ChrisP58]

Regardless of how you choose to arrange the windings, you will need to go with much smaller wire than 24awg.

There isn't even enough area in that core for the primary alone.