Arduino Motor Shield to drive 12v DC Brushless Fans

Hey

Im looking to build a 12v DC fan controller with a temp sensor to dictate when and how fast the fan spins and cant see any reason why I wouldn't be able to just use a cheap DC Motor shield from ebay to drive the fan and control its speed.

As far as im aware a PC FAN is just a Brushless DC motor which operates at 5-12v with a relationship between Voltage supplied and the RPM of the fan. I would be using small fans drawing .09A each (between 6 and 8 of them wired together with a total current draw of around .72A)

Can anyone confirm that this is a plausible solution before I go ahead and order a motor shield from ebay? Can anyone foresee any problems I would encounter doing this?

I would be using something el'cheapo like this - - - > http://www.ebay.com.au/itm/Motor-Drive-Shield-Expansion-Board-L293D-For-Arduino-Duemilanove-Mega-UNO-/280844181299?pt=LH_DefaultDomain_15&hash=item41639e1f33&_uhb=1

Anyone?. :blush:

Were you able to get this to work with the motor shield? I am curious and I am working on the exact same project.

L293, L298 do not vary the voltage presented to the fan. They are full on, or full off. What you can do is enable them from a PWM pin (using analogWrite) and control speed by the amount of time they are enabled. Lower numbers are slower, higher numbers are faster.

I don't think that brushless PC cooling fans are at all common and I don't know whether the fan you're planning to use is really a brushless fan, but if it is then you need a specialised controller. An Arduino motor shield designed for brushed fans is no use at all.

If it's a brushless fan with some sort of integral controller then you need to know what sort of signal the controller wants.

If it really is a brushed fan you have then you'd be trying to switch a total current of under an Amp. There are plenty of motor driver boards and shields capable of doing that and there are also clones such as the Baby Orangutan which have a suitable integral dual h-bridge driver - this would work out much cheaper than a standard Arduino plus shield.