DC fan

[juice_e]

Im looking at this fan to use for my pj.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=6835335838

Is this too much airflow? Because it seems like a hell of alot compared to most fans. And will it be too loud?
Also, soed it matter if it is AC or DC?

 

[germax]

Usually more airflow means more noise.

Noise is defined in decibel.
Your fan is rated at 53 dba which is a lot.

Here you can lookup some references:

http://www.lhh.org/noise/decibel.htm

You will need better fan.
If you are close to Princess Auto im Mississauga they have neat fans.
Also Active surplus downtown Toronto has some.

I can recommend you what I got so far if any of this is close for you.

 

[juice_e]

Theres a princess auto in Hamilton actually. I never knew they sold fans.... how much though?.... I just ended up buying that fan like 5 minutes ago before you messaged me back.

Is there a point in using this fa? It obviously has more than enough CFM but will the noise be WAY too loud or will turning up the volume a bit drown the noise. My PJ will be about 2 feet in front of me.

 

[germax]

I am sure it will be too loud.
Fan that I got in princess auto is completely different.
It looks like long cylinder with motor on the side.

I don't have it here, I can get more info over the weekend.
It kinda looks like squirrel cage...

Here is picture of the similar model

http://www.smcelectronics.com/FN04.JPG

It was 15$ and it is 115 volts so you do not need DC adapter for it.
Moves a lot of air and it is pretty quiet.

 

[imix500]

I use two of these fans in a solid state air conditioner I built and they are indeed loud. They kick out a good amount of air, and reducing the voltage a bit helps, but still kinda loud.

 

[doublejack]

I agree with germax, 53 dba will be much too loud. However, you may be able to still use it. That fan pushes a lot of air at 12v. If you cut the voltage it will spin more slowly, moving less air but also operating more quietly. At 6v it should still provide good airflow. If you put it in the interior of your projector enclosure that will also reduce the noise level.

A good benchmark for a 12v fan is less than 30 dba. That's where they start getting pretty quiet.

 

[juice_e]

Ok, that makes me feel a bit better ... how would i reduce it to 6 Volts?

 

[dnsey]

In case anyone's looking for other sources etc., those are called tangential blowers.

 

[doublejack]

To run the fan at a lower voltage you have a couple of options.

One is to use a lower input voltage. For example, if you are going to use a computer's power supply to operate the fan then you could use a power lead from the 5v rail instead of the 12v one. I typically use this method when I want to make a computer more quiet.

The other option is to still use a 12v power source but introduce resistance in series with the fan. This is the same principle dimmer switches use to control the speed of ceiling fans. One way you could do this is wire 2 120mm fans in series, with each then getting 6v. Another way would be to use a resistor. An adjustable or variable resistor (potentiometer) would be ideal because you could fine tune the speed and noise level of the fan. In the US, you can find potentiometers in Radio Shack and electronic supply stores.

 

[juice_e]

I have a bunch of dc plugs for like, an atari, gameboy, alarm clock and they are around 6volts... one is a motorola charger plug thats output is 4.8 volts at 350 mA. And i have an ac/dc universal plug that i can set to 6 volts, could i use that?

 

[doublejack]

Yes, you can use dc converters like the ones you mentioned to power a fan. A typical 120mm fan uses something around a third of an amp @12v so a 350 mA supply should be sufficient @ 4.8V. But I recommend caution at first, you don't want to start a fire