Arduino UNO: CPU FAN Similutator

An extension of Temperature over LCD project, this wants to be an example of old computer components reusing.

With an LCD, temperature sensor, optocouplers, two switches and some resistors, we are going to create a digital controlled CPU FAN.

In this example I'm using a 3 wires 5V fan, in order to powering directy with Arduino 5V pin.

It will possible to set a threshold temperature using two switches, one increments and the other decrements, in order to tell Arduino when switch on fan. If actual temperature is greather then threshold temperature, fan will switch on.

What to know about CPU fans

Exists different kinds of fans, with 3 or 4 wires. First ones has GND, Powers supply and output wire to communicate rpm, second ones instead use the 4th wire as a PWM power supply, in order to set rpm.

Another thing to know is that 5V fan usually operates with 400mA, that's generate noisy on Arduino lines that could damage internal voltage sensors. So keep thisprojectjustaeducationalpurpose,notasaprofessionalcircuit.

What to know about OPTOCOUPLERS

Are a simple switch, that use an internal LED and foto-resistor in order to close and open the circuit. If LED is on circuit is closed and "electricity" can pass, otherwise not.

To turn on/off the LED just use a LOW and HIGH digital output from our Arduino, with a resistor in order to not burn it.