[sdiy] switched mode PSU design

[fmg]

Tim Parkhurst wrote:
> 
> What I'm looking for is info on winding the inductors. Given the
> component values you suggested above, is there a program or a formula
> that will show me what gauge wire and how many turns? Are these
> inductors (or values fairly close) things that I might find in the
> local surplus shops (we have a couple of very good ones here in the
> Silicon Valley)? Also, I'm not sure what you mean by the cap values
> (e.g., 100pF + 1nF). Are these in series as one 'leg' of the Pi?

100pF ceramic in paralel with 1nF plastic, my poor way to make an *ideal*
capacitor from real ones (made of diferent stuff, with diferent behaviours
at diferent freq bands)

Your best reference for coil making is the ARRL Handbook (the older the
edition the better), also good info can be found in most ham websites.
A fast google:

http://www.qsl.net/yo5ofh/doc/radio%20calculs.htm

That's the most pop formulas for radio. Personally I prefer:

L= mu * 1.257 * ((n^2 * a)/(10^8 * l))

[L=Henrys, mu=core type (1=air 30=typical for ferrite rods), n=number of
turns, a=core area, l=coil lenght, all measures in cm] ... which gave me
good results throu the years.

Notice that these formulas are gross simple and intended only to be used
in the bench, you can success or fail, depending on the application.
(don't use them to make your new particle_accelerator_solder_gun... ;-)

Regards,

Fabio
.