Computer Case fan question

[grrr_arrghh]

Hi

Computer question:

I have a case fan that I got out of an old computer. its a JMC Datech, DC 12v 0.6A. My motherboard (Asus A7N8X Deluxe) has a chassis fan connecter with 12v, ground, and rotation connections. (my fan has three pins, so I assume they will be the same...).

However, my motherboard manual says "...connectors support cooling fans of 350mA (4.2Watts) or less". Now I was under the impression that 0.6A was 600mA? If so, even if this 350mA is for each fan connector (rather than all together), then I will overload it and wreck my motherboard.

The fan is only about 8.5cm (3.25 inches) accross, this seems like alot of current for a fan that size.

So..

1) Do you think the rating is a misprint?
2) Can I connect the fan directly to my power supply (bearing in mind it has the connection for 'rotation')?
3) Can you get fans of that size, but that use less current?

Thanks

Tim

 

[ChrisP]

Did the fan that yopu have come out of a power supply? I'll bet that it did... Typical case fans are on the order of 150mA (+ or -), and are readily available from amny sources.

 

[grrr_arrghh]

no, it didn't (u lost the bet :lol: )

however, I had a look at the old comp again, and I realise now why.

The proccessor had a large heat sink on it, with a sort of cowling, and the case fan (the one I took) drew air through the cowling, and accross the heat sink. That is why it is so powerful.

150mA sounds more like it, lol

thanks

Tim

 

[ChrisP]

OK -- here's some more info... The image below is the results of a search on **broken link removed** for Fans > DC Brushless > 80mm x 80mm x 25mm > 2 ball bearing:

**broken link removed**

Here is a link to a popular 3-lead 80mm ball bearing case fan from Kingwin -- 130ma/25dBA/32.4CFM/2.48W ratings for comparison purposes. This is typical of the case fans that I stock here.

 

[grrr_arrghh]

ok, thanks

i'm away for the weekend, but I shall have a look at them when I get back (I am in desparate need of more cooling, as my case was designed for a much lesser computer...)

Thanks again

Tim

 

[Nigel Goodwin]

what if you put a resistaqnce to limit the current?

The fan will run slower, rather defeating the point of adding the fan.

 

[bogdanfirst]

the thing is that the old fan might be the brush king of one. and another thing is that not necessary the fan is more powerfull, but the technology used today is more advanced, so the fans of today to the same thing as the old ones but more effiecntly. i suggest you buy a new fan, even if it is not the kind that connects to the mainboard. you could use a simple fan with just 2 connectos. some can be connected to the power suply directly.
i mean, if you use a case fan, i don't think is it really importanat to know the speed?

 

[grrr_arrghh]

i agree, you don't really need to know the speed, it just would have been easier to connect to the motherboard...

it isn't a particularly old fan (maybe 2/3 years old) and it is a brushless one, i think it was just a more powerful than normal fan.

Thanks for all the suggestions

Tim

 

[evandude]

you can wire the power for the fan to a connector from the power supply, and run the rotation sensor wire to the motherboard. the power supply can obviously output 600mA to it, and the motherboard still gets its rotation signal. new case fans are only a couple dollars, but there's always the hassle of ordering one, or going out and buying one...

 

[grrr_arrghh]

ah, thanks. You don't think my motherboard would get confused if there was no power being drawn? (or will it not sense that...?)

yeah, why spend a couple of dollars when you can spend nothing...

thanks everyone

Tim

 

[evandude]

I've seen case fans that just come wired that way (power and ground wires to a molex power plug, single rotation sense wire going to the three-pin motherboard connector)

 

[grrr_arrghh]

cool, thanks

just out of interest, if was to connect the4 rotation sensor to, for example, an LCD pannel on the front of my comp, what is the rotation signal. is it a voltage level (higher the faster or something?)??

 

[evandude]

I think it just outputs quick pulses, like one pulse per revolution or something like that.

 

[grrr_arrghh]

oh, ok thats nice and simple

thanks to all

Tim