[lawdawg]

I want to add a couple of low db computer fans to my hushbox, but do not know how to power them from a wall outlet. I have been reading about converting AC to DC, and such, but am not sure what I need. Is there a device, that is readily available to do this? Or something fairly easy to build?


Thanks in advance,


------------------

Adam

 

[tbshooter]

Quote:

Originally posted by lawdawg: I want to add a couple of low db computer fans to my hushbox, but do not know how to power them from a wall outlet. I have been reading about converting AC to DC, and such, but am not sure what I need. Is there a device, that is readily available to do this? Or something fairly easy to build? Thanks in advance,

You can get an AC-DC power adapter from Ratshack. I presume you are getting 12V computer fans. Just add all the current draws from each fan and double it to give you the current rating for the power adapter you need (e.g. 2 fans that draws 200 ma each, (200+200)x2=800 ma therefore any adapter that have a rating of greating than 800 ma would be fine).

 

[JoeFloyd]

It would be easier to use fans designed for AC. There are many small "computer" type fans that are actually AC. You won't see these at the computer store, but electronic supply houses will have these instock.


A favorite place for me to shop for little odds and ends is All Electronics.

http://www.allcorp.com/


They also have power supplies that will convert AC to 12v DV which is also just what you need. On the home page listed above there is a 150watt DC power supply that would work in you application. It's only $10.50. One thing to keep in mind is that these power supplies are meant to be used in an enclosure. They have exposed components that would be dangerous to children or pets.




[This message has been edited by JoeFloyd (edited 07-31-2001).]

 

[lawdawg]

Thanks guys. I was interested in this because I hope to use the following fan http://www.pcpowerandcooling.com/pro...rfan/index.htm

mentioned in the HTPC forum for its overall worth/quiteness. But will check the All electronics for an equally db rated fan.


Thanks again.



------------------

Adam

 

[lawdawg]

Joe,


That sounds like a good idea, unfortunately my custom built hushbox is on the floor. I was hesitant to cut my celing, and or floor. So I made a box using a glass end table as the frame and then "building" the box around it. It is lined with sound absorbtion material, and cuts down on the noise significantly. Currently I am using a rectangular window fan purchased at Wal-Mart to push the air from bellow and out a vent cut in the top/back of the box. The problem is this fan is nosier than the projector fan, and it's the quitest "real" fan I could find.


The box has a hinged front with a window of edmund scientific glass, and is covered in black velvet. I then put one of the glass pieces back on top of it. It actaully looks pretty good. It is not completely sealed with openings on the bottom for cool air to enter. I just need some quiet fans to help move the hot air on the top level out the back. Hence the need for smaller/quieter fans.



------------------

Adam

 

[cubTO]

Use 12 V DC fans, and get a 'wall wort' power supply for them....you don't need a 150W supply.

 

[dcarl]

I've got cooling fans all over my system, including a crawlspace that contains the PJ. Just some ideas: I use some fans designed to run on 220VAC, but connect them to 120VAC. They don't move as much air, but they're dead quiet. To get the same effect when using two fans, hook them up in series, that is, a daisychain connection between the ac cord and the two fans. This works with either AC or DC fans.

These might not move enough air for a hushbox, though.

I'd use double-sided foam tape to mount them on anything, instead of hardware.
www.jameco.com has a pretty good selection.


-Dave

 

[JoeFloyd]

In order to keep the sound inside the box you need to either have baffles in the box (this makes the box big) or vent the projector into another area. With baffles it may be important to use quite fans, but with ducting you can mount the fans in another location. I've seen one installation that had a custom filter box to pre filter the intake air before being sent to the projector. The guy used a standard bathroom vent fan which was pretty noisy, but since it was in another room it wasn't a problem.



Just and a idea, why not place two standard vents in the room connected to a blower box that is mounted in the ceiling. One vent for intake and one for exhaust. The blower box routes the air through the hush box. Using flexible ducting isolates the vibrations and should result in a very quite installation. Some care might need to be taken to ensure the blower box doesn't vibrate the ceiling and that it's accessible for filter changes and other general up keep.



[This message has been edited by JoeFloyd (edited 07-31-2001).]

 

[bluedevils]

if you're still into the computer fan, you can just go to a mom and pop computer store (one that custom puts together computers) and buy a power supply for a computer. I bought one separately for my computer($10). In fact you would be able to attach a few fans with this power supply. The question is would this move enough air? I'm not sure about other projectors, but I would think a DILA would need more air movement.

 

[Kjelt]

If you use 12 V fans buy a simple power supply which lets you choose the Voltage with a switch. Then try setting the switch lower as 12 Volts (like 9 Volts) this will drop the fannoise dramatically (ofcourse less air is transported)




[This message has been edited by Kjelt (edited 08-02-2001).]

 

[AlMark]

The Whisperflow uses 80mm fans with a 12v wall transformer, so something in that size with a 30cfm rating should do the job.


Al

 

[cubTO]

"...since the voltage is down the current will rise a little bit"


Not quite, that would break ohms law.

 

[Kjelt]

cubTO: "breaks ohms law"


You're right I was sleeping, my first thought was that if the fan runs slower it gets more friction so needs more power so it needs more current. But to see a fan as a simple resistor is still not my view: It is a motor which has coils.

Anyway you're point is right, less voltage less current but most important: less noise.


[This message has been edited by Kjelt (edited 08-02-2001).]