hello everyone can i do this:
hack a led matrix to replace the leds in the system with computer 12v fans?
i would like to use:
arduino --> shiftregisters and a led driver for the columns an rows ------> Matrix with 12x12 fans with 12v 0.2A
thank alot
bernard
Yes you can PROVIDED that your drivers can handle the extra current.
Most LEDs take only 20mA so you are asking for 10 times the current.
Also with a matrix the LED effectively flickers on and off too fast to see, with fans this will have the effect of reducing the speed / power of the fans.
I think you would be better off just using the shift register or some other port expander.
Anyway why do you need 144 fans?
Maybe he wants to make a HUMONGOUS cooling system for his OC'ing needs 
.. or maybe a hovercraft .. lol .. or an air compressor? .. or a gigantic leaf blower?
j/k
All the best with your endeavor
hey grumpy mike i am doing my audiovisual instalation with smoke and wana make a simple interaction with it...
the power converters will be aplied one by each column and one by each row?
and do some hovert crafting
OK best of luck with it. 
EDIT
Just had a thought do you want to control the direction of the fans? Sucking and blowing.
no grumpy just turn them on and offf
may i know why?
On/off control will be easy, but not reversing. A PC fan usually has a brushless DC motor in it, and they cannot be reversed simply by reversing the polarity of the supply (like you can with a plain DC motor).
Remember to use an external power supply that can supply enough current to run all those fans. And of course, you'll need driver circuits to switch the current, and Mike has suggested. Have you seen the ULN2803 chips? They give you eight drivers rated at 0.5 Amps each.
All I can say is: darlington
If your using fans I would use a daisychain of shift registers and buffer all the outputs. ie, no multiplexing at all
You would need 18 shift and latch registers (4094s or 595s) and a way of beefing up the current out of the registers, darlington arrays are your friend here.