I am working on a project to blow air gently through a number of pipes and variable speed. I would like to use a standard PC case fan and have control of whether the fans are on/off and also what speed they spin at. My hope is to attach temperature sensors later and eventually blow are depending on the temperature.
It appears that PC fans on 3-wire and 4-wire systems provide variable speed by changing input voltage ranging from 3-12V (linear voltage regulator) or with PWM set to 3.3V or 5V. Furthermore, it looks like inexpensive products exist to split/copy a single signal to multiple fans (see here).
I am hoping to control 4-8 fan speeds, as independently as possible while using as simple/standard a case fan as possible. What is the best way to drive PC case fans using the Arduino?