PWM v Voltage regulation - nice summary article

davidstone28 · Post by **davidstone28** » Thu Oct 21, 2004 2:11 am

http://casemods.pointofnoreturn.org/pwm/index.html

sthayashi · Post by **sthayashi** » Thu Oct 21, 2004 7:57 am

That article wrote:CON: A fan pulls more current at lower voltages.

BULLSH!T!!

ferdb · Post by **ferdb** » Fri Oct 22, 2004 11:12 am

Heh, yeah. And PWM on the fan is not going to shorten coil life, and the statement that voltage control doesn't let you run your fans slow is misleading also. But there is usefull information in the article.

cpemma · Post by **cpemma** » Sun Oct 24, 2004 9:22 am

On linear control:

MAJOR CON: The excess voltage needs to be dissipated somehow - with the exception of the 7-volt trick and stepdown transformers, all of the solutions above dissipate it as extra heat in the case - and a lot of it - which defeats the purpose of fans.

I'd argue that any form of speed control reduces heat in the case. Less fan currrent, same overall 12V, so less watts. Two different lesser heat sources instead of the one at the fan.

PWM reduces it most, but in the context of sensibly-rated fans, coupled with high-speed processors and graphics cards, it's hardly a major impact.

Pro's of PWM (IMHO) are;

A very compact controller can be put together; no need for bulky heat-sinks or even TO-220 semiconductors.
More reliable fan starting at low-speed settings without kick-start circuitry.
Almost the full 12V speed available if needed without expensive LDO regulators. Switcher transistor loss around 200mV compared to a regular regulator's 1.5V minimum.

The major con is a common noise problem at low fan speed.

Rizban · Post by **Rizban** » Sun Oct 24, 2004 10:40 am

Does anyone have the circuit for a Zalman Fanmate? I am curious how a fanmate reduces the voltage of the fan without absorbing several watts in a resistor.

Cerb · Post by **Cerb** » Sun Oct 24, 2004 1:08 pm

Rizban wrote:Does anyone have the circuit for a Zalman Fanmate? I am curious how a fanmate reduces the voltage of the fan without absorbing several watts in a resistor.

It does take it in the resistor; it just has a pretty plastic box around it.

Jan Kivar · Post by **Jan Kivar** » Mon Oct 25, 2004 6:42 am

Rizban wrote:Does anyone have the circuit for a Zalman Fanmate? I am curious how a fanmate reduces the voltage of the fan without absorbing several watts in a resistor.

It's basically like this, Zalman just went on the cheap and left the caps out.

Cheers,

Jan

Rizban · Post by **Rizban** » Wed Oct 27, 2004 7:51 pm

Thanks for the link. There is lots of interesting info there.