Arduino temperature controlled PC Fan
This article was submitted by Oscar Gonzalez distributed on uchobby.com.He descript  a simple tutorial for speed controlling a PC FAN and reading a LM35 temperature sensor with an Arduino microcontroller. He covers the use of an optocoupler, PWM (Pulse Width Modulation) and reading analog voltages with the Arduino. He even has a video showing the fan speed control in action.
   Arduino temperature controlled PC Fan
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