Computer Fan??

[chris17]

I was reading a while back about some people useing computer fans to keep their lights and tank cool. I could't completely remember (part of my problem) how it all went together. I picked up a computer fan, a 120mm DC Fan. I thought I read that you could match up a fan with a phone charger or something...idk i am lost and need help lol
Here are the specifications of the fan I got...
Fan Dimension- 120x 120x25 mm
Started Voltage- 6V/7V Max
Rated Current- 0.38A
Power Input-4.56W
Fan Speed- 2000+ -10%RPM
Max. Air Flow- 78CFM
Max. Air Pressure- 2.97mm-H20
Connector- Molex 4Pin
If anybody can help me out it would be greatly appreciated. I am going to keep trying to find info on this, but if anybody has done this and can shed some light on the subject please do.
Thanks
Chris

 

[crazydave]

I am using computer fans that I mounted to my canopy. The difference is....is that I bought the 110V AC fans from radio shack.
Now if I were to use the DC powered ones....I would buy 12V and use a power supply. Dont know that I would trust the charger type power supplys that plug into the wall. Maybe can be done....but not my style. I like the 110AC type and wired those into my lights so that they come on together.

 

[scsinet]

You'll need a power supply. Most people match the voltage to the fan, so a 12v supply with a 12v fan. Current has to meet or exceed the fan's draw, but I always like to have a little extra so as not to run the power supply so heavily loaded. So if you have a 0.38a (380ma), you'll need a power supply that can do 12 volts at 500ma or more.
So basically current must be equal (with a little overhead) or greater. Voltage must be equal or somewhat less, but not too much less.
Some folks also like to run their fans at reduced voltage to reduce the noise level. 78cfm is a fair bit of airflow, so the fan may run a bit loud for you. In that case, you might try a 9v supply, same current rating. Running at reduced voltage sacrifices airflow.
You can get a power supply at Radio Shaft, but you wouldn't be a true frugal reefer if you did that. I prefer to go down to my nearest goodwill store. They usually have a basket of various power supplies for like $1 each. Just dig till you find. 12 volt supplies are REALLY common, and 500ma-1amp/1000ma are the most common of them all.
Then just splice, seal your connections well since seawater corrodes copper very easily, and you're good to go.
If you have a 4 wire fan, that's what's called a PWM fan. These fans have four wires: positive, negative, tachometer, and PWM. The tach and PWM are so the computer they are plugged into can read the speed of the fan and set the speed of the fan, respectively. Luckily if you ignore these wires, the fan will ignore them too and just run at full speed. So just cut them off (AFTER you test to make sure you are connected to the right wires!!!). Usually the four wires if I recall are black, red, yellow, and blue. Black is your negative, red your postive. Cut blue and yellow off and don't connect.

 

[chris17]

Thank you crazydave and SCSInet for your fast response. I am not very techy when it comes to putting things together, but I try. I will get to a goodwill asap and try to find a 12v supply. I will probably go tommarow, so I will try and get everything then. Thank you again for your help

 

[scsinet]

Make sure the supply is 12 volts DC, not AC. AC output supplies are less common, but are out there...

 

[chris17]

Just got back from Goodwill, picked up a 9V 350ma power supply. The goodwill here isnt very big and didnt have many... mostly regular small power cords. Got everything wired up and it works great. I am pretty sure that it is not running at full speed, but thats fine. I will keep looking for a 12v, but the 9v works well. I will probably be getting another one of these fans, 10 bucks at the shack. Thanks for the help!

 

[scsinet]

You're a little under the current rating, a 380ma fan on a 350ma power supply, but usually when you reduce the voltage the current draw drops as well. Without putting a meter on it it there isn't any way of knowing for sure, but in all likelihood you are a-ok.