You did not mention reversing the fan direction, so it is not clear why you would need an H-bridge (like L293).
A simple power NPN transistor would seem all that is necessary to control the group of fans.
it is not necessarily the case that the Lamptron (and similar) controllers use voltage to vary the speed of the fans. It is more common to use PWM to control the speed of DC motors. Except for the case of fan motors which have a speed control input. But the fan you specified does not appear to have this option.
You seem to already have the "how would I power" question answered. You said that they will be powered from a PC supply. OK
The question "how I control the group of fans" seems almost as simple. Use a single power NPN transistor to switch the current to the fans. Either simple on/off, or using PWM to control speed (same circuit either way).
But if they use PWM instead how do they control fans that does not have PWM support?
QuoteBut if they use PWM instead how do they control fans that does not have PWM support?No all motors will respond to PWM, do you understand it?:-http://www.thebox.myzen.co.uk/Tutorial/PWM.html
I do know how PWM works. The fan does not have natively support for PWM (the fourth pin for control input) so to use PWM would require a component and would that be better then voltage regulation?
This is the typical circuit used to control a load like a fan or a solenoid from an Aduino pin:That circuit will work just as well for multiple fans as for one fan.That circuit will also work for PWM control of fan speed.
Then if you think that you don't know how PWM works, please read the link I posted.PWM needs no support either third or fourth pin on a fan.
the TIP120 can handle 5A is just what I need
Quotethe TIP120 can handle 5A is just what I needIf it is "just" what you need, then you may actually need something a little meatier, to handle peaks and variations.
It is not good practice to use a parts at their maximum ratings for steady-state conditions. A peak startup current of 4A for a 5A rated transistor is fine.
So said Transistor could be used to VARIABLE speed,