I built a cabinet for a few pcs but the fan is too noisy and soft mounts haven't worked, any way to vary the speed of this motor? Router speed control and incandescent light dimmer won't work, is the only way to go DC12v w/ rheostat?
Tom
How about using two fans, quiet and slow and fast and loud, and turn the second one based on a temperature switch. Cheap (relatively speaking) and easy and relatively reliable.
iAccording to tom :
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Then you *can't* practically adjust the speed of *that* motor. It is an induction motor, and locked to the power line frequency.
It might vary a bit on a VFD, but probably not enough to be worth the cost -- and the cost of the VFD would be *way* above the cost of a new DC fan designed to be varied by voltage.
Go for either a 12V one or a 24/28V one -- with 12V probably being easier to find in a typical computer chassis.
Of course -- you *could* replace your 28W one with a 14W one, and reduce the noise (and the cooling) somewhat. But the reduced cooling may not be a good idea.
Enjoy, DoN.
Check with Jameco or Mouser electronics. Buy a 24v or 28vdc fan and run on 12 vdc. We did this years ago to knock down acoustic vibration on Mil spec equipment.
Jim Vrzal Holiday, Fl.
Use a Variac (Powerstat) auto transformer. I have two 10" fans in an equipment cabinet that have been running that way for years. They don't produce enough heat to be harmful at the reduced voltage and they are quiet. Probably a 2 amp or less is all you need. Check the motor rating. Respectfully, Ron Moore
Muffin fans are going to resist being controlled unless they are designed to be controlled. AC or DC they're almost all brushless designs - or they'd never get the service life out of them.
They make speed controllable models, the cheapest way is to shop the PC Modding shops with the fancy LED lit cases - they have fans with front-mount controllers for manual or thermostatic control.
The other way is to check other fans that will fit in your application - they often make the same size and airflow both in noisy and quiet versions, it's all in blade tip speed and airfoil design.
If your exhausting system has high back-pressure between pushing out and pulling in, try using a squirrel-cage blower instead of a fan - they can operate against an inch or two WC in the ducts with efficient flow and without getting noisy.
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Ceiling fan speed controller might work, but that's a small AC motor. Some of the cheap three speed box fans have a small tapped inductor that might work.
Put a 15W 120V incandescent lamp in series and see if the speed is near your needs. Muffin fans that are shaded pole induction types respond to voltage control because of the inherent voltage/torque curve vs the fan speed/torque requirement (also called the "fan laws") If the speed is wrong, change lamp wattage to get what you need.
Randy
I've done this by putting plastic film or oil-paper capacitors in series with them. Usually something in the 0.1 to 0.47 uF range, 250 V minimum rating. It is fairly tricky to find the right value as the backpressure load on the fan greatly affects the speed when you run it like this.
The best solution is if you can get a Rotron "Whisper" fan, it will turn very slowly and can rarely be heard except in a silent room.
Jon
"Bruce L. Bergman" wrote: (clip) AC or DC they're almost all brushless designs (clip) ^^^^^^^^^^^^^^^^ I'm drawing a blank here. Tell me about brushless DC motors.
A DC brushless motor uses a sensor for commutation. For example hall effect sensors. So as the rotor spins the hall effect device senses the change in magnetic polarity. This is then used to change the polarity of the current running through the stator windings. Most of the ones I've seen are three phase motors. If you can, get an old floppy disc drive and take it apart. You will find a disc magnet rotor that sits above a circuit board. The circuit board will have flat coils on it. and you should see three tiny black rectangles soldered to the board. These will be the hall effect sensors. Of course fans are not flattened but they work the same. ERS
Brushless motors use solid state switching to performthe commutation function.
Brushless dc mtors are very common in the electric powered radio control hobby market. Incredible torque and controllable speed. Not cheap but really nifty. The whole outer case turns on some of them.
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