I use the Smart Servo Controller to show how you can easily control two fans with a temperature sensor
We are going to have the LED blink at about on and off on one second intervals (0.5Hz). Fan 1 will turn on at 46C temperature. Fan 2 will turn on at 60C temperature. To have some hysteresis both fans will turn off at 30C temperature.
Connect the Microchip MCP9700 temperature sensor up to input channel 1 on the smart servo controller.
Go to the IO Setup Tab,