I went looking for the article I mentioned above on PWM’s and found it. The site is on a DSL line. So, please go there only if you are interested in the construction (soldering skills involved) of one of these devices. Yes I got permission to link to the site from the owner.
http://casemods.pointofnoreturn.org/
there are 4 nicely done tutorials here. 3 of which were of interest to me.
Tutorial for building a voltage regulator for fans based on the LM317 chip.
Tutorial for building a LED voltage monitor for rheostats/LM317/PWM circuits.
Tutorials and theory for building low-heat, high-amperage PWM fan controllers.
The 4th one is:
Tutorial and software for a LED meter that can display POST codes and CPU/memory/network/harddrive/etc. utilization.
I need to do some studying here to see if I can modify my $5.95US Radio Shack PWM for variable frequency. Or I may decide to wire up one of his circuits on a perf board.