Hi!

I wnat to use Arduino to control 8x8 electronic fan matrix(fan grid,fan array),just like the following graphic.(in next post)

I have used TIP120 transistor with PWM out mode to control the speed of fans.(thanks for ITP provide Tutorials: in next post)
My previouse work：Unheeded Advice(in next post)

Standard Arduino like Duemilanove, Diecimila, just have 6 PWM output pin to use, even Arduino Mega only provide 14 PWM output pin.
All of them don't have enough PWM pin to control 5x5 or 8x8 fan martix.

Are there any IC chpis can be used to control 5x5 or 8x8 fan martix?
And how to use it?How to program?

Thank you!  

A matrix of LEDs is normally controlled by multiplexing but you can't do that with fans.

Your best bet is the TLC5940, this gives you 16 PWM channels per chip and as it is an I2C device you can put up to 8 chips on the bus without resorting to any tricks.

However the chip itself will not be able to delver the current for the fans by itself. Assuming these are 8mm fans they take about 120mA at 12V so you will need a transistor driver on the each output of the chip.

There is a library to drive this chip and it contains examples of how to use it.

As a matter of interest what does the participant experience with this? Apart from wind.  

Do the fans need to be individually controlled?  The TIP120s have very high gain,  and should only need a mA or two to drive a fan.  So you could drive several from each Arduino pin.  Or add a simple transistor or opamp buffer to drive even more.

Ran

This tutorial might help:
http://www.arduino.cc/playground/Learning/TLC5940

You might also consider the ULN2003 or ULN2803,  because they have a higher current rating per channel (but also waste more power,  because they're Darlingtons instead of single transistors).  They also have the protection diodes built in.

Be sure you look at the total power for the whole chip:  even though you can sink 500mA per channel with the ULN-series chips,  you can only do that on a couple of channels at a time if you're running them (almost continuously).  And you may want to put a heatsink on the chip to help keep it cool.

Or just mount the board so that the fans suck all their air past the chips  

Ran