I noticed they come in various colors. Yellow-white is the most common in the computer PSUs.

What do those colors mean? Can I know the details about the core that would help me wind my own inductors without LC meters and stuff from the core's color?

 

Hello,

Perhaps the following page might give you the information you want:
http://www.electronics-tutorials.com/basics/toroids.htm

Bertus

 

Thanks a lot!

 

There is this little free program an the net which help you to calculate ringcores.
http://www.dl5swb.de/html/mini_ring_core_calculator.htm
It gives You also the color markings of some core materials.
Notice that some modern and popular chinese cores have different color codings.

 

Most of my cores are from old computer PSUs, you think it'll work for them?

 

Toroid colors don't always have a "universal" meaning. One can order toroids in custom colors from the manufacturer for your in-house markings. Toroids for power conversion frequently have coloring that is only meaningful to the manufacturer of the power supply, where RF toroids used in filters, etc. use a more standard system as Bertus referred you to.

For your purposes, I would have to say no. Wind on 20 or so turns, then read the inductance and calculate the AL from there - or use the Mini Ring Core Calculator for the last step.

 

Toroid colors don't always have a "universal" meaning. One can order toroids in custom colors from the manufacturer for your in-house markings. ...

I'll second that, I've had powdered iron toroid cores made to spec for commercial product and they just asked what colour coating we wanted. I chose a colour that had a high contrast of wire colour to toroid, to enhance visibility and turns counting during hand winding. They also looked good.

The yellow/white ones salvaged from PC PSUs etc are usually a low frequency powdered iron type, they are ok for home made SMPS inductors and transformers.