Power Supply Whine

[seibu]

Hi,

I'm building a cocktail cab and have added a 5" 12v fan into the side of the cab for cooling. I'm powering the fan from a normal PC power supply. The problem is that the fan is far too loud.

So, I tried running the fan from the PC power supply's 5v line rather than the 12v. It works great when the PC is switched on - the fan goes nice and slow and is virtually silent.

The weird thing is that when the PC is switched off, but the cab is plugged in (ie. there is mains power going to the power supply, but the PC is off and theoretically there shouldn't be any power being supplied to the fan by the power supply) the fan motor (or the power supply - it's hard to tell) whines quite loudly.

I don't mind the whine (the PC is obviously switched on only a few seconds after the cab power is supplied, at which point the whine dissapears). But am I killing anything?

Is there maybe a better way to get the fan to slow down? By using the 12v line and fittting a resistor, perhaps? Basically, can anyone can tell me with reasonable confidence that I'm not slowly killing the fan or the power supply, or advise of a better way to slow down the fan?

Thanks!

[juggernaut]

you could run a variable resistor inline with the positive connector on the fan.  that would give you a variable speed control.  what kind of noise is the fan making that you need to slow it down?

[seibu]

you could run a variable resistor inline with the positive connector on the fan.  that would give you a variable speed control.  what kind of noise is the fan making that you need to slow it down?

Thanks! Yeah, that would be cool, I'll look into it. Any idea what specification of variable resistor I would need? The fan claims to draw 500 milliamps at 12v dc.

The fan is just generally too loud going at full speed. It sounds like a hovercraft or something. It shifts a serious amount of air - since it's a big fan the cab will be cool enough with it going a lot slower.

[danny_galaga]

fans are cheap, buy another one!

[juggernaut]

as for the resistor, start with something like 100k or 250k just use the center post and the left one(post #'s 1 and 2)

[wboy]

I had the same problem when converting my cocktail.

The original fan off the mains was way to loud for my (and my girlfriends) liking.

I purchased a Sunon 120mm, 120cfm ($21AUD) fan along with the following:

http://au.store.yahoo.com/davidandkarma/spirsinfanco.html

Cheap ($6AUD) and works beautifully!!!!!!  Very easy to take the bracket off too!  The two are a perfect solution actually!

I also bought this one ($12AUD) just incase the one above wasn't sufficient and it seems to regulate the power too much not allowing me to as much variable control or maximum output compared to the cheaper one above!?!?!?   Not recommended!

http://au.store.yahoo.com/davidandkarma/spirdualfanc.html

EDIT: The site also has all the required connecters to easily hook the fan & controller to the power supply.

[bdsjake]

another thread recommended "panaflo" fans, I don't remember the site but I am sure you could google it.  I bought one and it is fairly quiet.