My children asked for a desktop fan to cool them when doing homework. We used a Kniwwelino and a Arctic F14 PWM fan. The cool thing about the Artic PWM fans is that you don't need any power transistor to change the fan speed. You just have to add a PWM signal to the forth pin of the cable and you are done. To have 12V for the fan I use a step-up converter that comes with a handy micro-USB connector.
- 5V for Kniwwelino are taken from the step-up input side and connected to the battery connector of Kniwwelino.
- Adjust the output voltage of the step-up to 12V.
- 12V for the fan comes from the output of the step-up and goes to the flat 4-pin cable of the fan. As the cable is all black you have to be careful. There is a white mark on the first wire that indicates the ground. Next wire is the 12V plus pole. Then the tacho impulse to read the speed. Last one is for the PWM signal.
- connect the 4th pin of the cable and the ground by a 4.7k resistor to prevent that the fan runs during the boot phase of the Kniwwelino.
- connect the 4th pin of the fan by a 1k resistor to the Kniwwelino D6 pin. The resistor is to protect the Kniwwelino pin.
Upload the firmware Fan.xml from the download by opening it in the online programming platform https://code.kniwwelino.lu