Thermally Controlled Fans (& 3-pin fan control...

I don't know if this should be in hardware or software, but since about fans, which is hardware, that's where I'm starting off.

Can someone explain (in simple terms) how a thermally controlled fan (such as the Akasa AK-179BKT-C http://www.akasa.co.uk/update.php?tpl=product/product.detail.tpl&no=181&type=Fans&type_sub=Auto%20thermal&model=AK-179BKT-C) works ? (or direct me to somewhere where there's a good explanation). Does it read the exhaust temperature, and adjust the maximum permitted speed, and then work in on/off manner at that speed as normal in a 3 pin configuration (but I dont understand how that works I've discovered...)?

Am I correct in thinking that in a three pin configuration, the fan is either fully on or off, depending on the set (or target) temperature ? So the speed sensor does nothing ? So, come to think of it I need to understand how a fan with three pins is controlled...

I am confused.

I'm thinking of a CPU fan, so the temperature being controlled is the CPU temperature. Usually the temperature of the CPU is known (there is Winbond sensor on my PC which can determine this)

Dumb_Question
10.July.2012
Compaq Presario S5160UK DT261A (Celeron 2.7 GHz) - MSI MS6577 v2.1 - 1.5GB RAM - XP/SP3

 

There are different methods to controlling speeds. If you look at your link, that fan uses a little (green) thermo diode that senses the ambient (room) temp, then adjusts the fan according to some algorithm they set. The warmer the air, the faster it spins. Not what you want. You want the motherboard's chipset to control your fan speeds, not the fan itself. It has no idea what it is cooling.

And note that fan is NOT for computers. Case fans are typically 80mm, 120mm, or larger. That is a 7cm or 70mm. If that is the same size as currently mounted on your CPU's heatsink, then it will physically fit, but again, the motherboard needs to control the speed.

As far as the 3 pins controlling speed, that is all up to the motherboard (chipset). Some 3 pins control speed, some just power.

Also note the heatsink fan assemblies that come with Intel and AMD CPUs are perfectly suited to keep those CPUs cool. If you are having heat issues, and the CPU fan is still spinning and the case interior, boards, heatsinks, vents are all clean of heat trapping dust and dirt, then you have another problem that a new cooler will not fix. Assuming you are not doing any extreme overclocking.

So if your current CPU fan is failing and you need to replace it, you need find one that fits an Intel P4 or Celeron using a 478 socket. But if you are having heat issues, it is your cases responsibility to provide enough air flow to the components inside. And of course, the case cannot configure, or clean itself.