Use of pulse width modulation

[Shadow Catcher]

There are a number of us that discussed using pulse width modulation to regulate a fan speed i.e. Fantastic Fan. I can now tell you firsthand that it works very nicely and with very little waste of energy, however there is another consideration when buying a module.
I got a module from Carl's kits made in Thailand that will handle up to 15 A to use with my bilge blower, in place of a set of resistors, and it works beautifully, except for one thing! It causes the motor on the blower to buzz as the pulse width increases to regulate fan speed. The solution to this problem is by a pulse width modulation unit that also regulates frequency, which I did not do. They're not particularly expensive and in time I will see how this works out and if the noise is objectionable.

[madjack]

...good info to know...I have been seriously considering a PWM to control my FantasticFan...nice to know the "pitfalls" to look out for.........
madjack

[oddie121]

I've been looking at PWM in some computer fans I've got. Any one have a diagram on how to wire up a computer fan that has this already built in? Or am i stuck using a potentiometer?

[GuitarPhotog]

I found a 3-channel PWM controller intended for computer fans at the local computer superstore.

It's nice, at the lowest speed I can't hardly hear the fan, at the highest speed, it produces quite a breeze in the TD.

<Chas>

[Lgboro]

I will have to test mine further to see if I have a buzz in my led lights or bank of computer fans. Of course I'm in a different country (eastern NC - hehehe) so I may be on a different frequency altogether. I didn't notice a buzz in initial testing but will test some more. I'm just wiring my tear now. The dimmers were a little of $40 a piece so I hope they will work

[Shadow Catcher]

The fan I am powering is a bilge blower, explosion proof and draws a couple of amps and puts out 200+CFM