Voltage control is done by LM317
and 2 NPN 2N3904 transistors, see design schematic. Fan controller was tested with SWiF2-800 Coolink fan
, however any standard case fans should work.Only basic calibration is required. 1 – Adjust potentiometer connected to LM317 till you get about 12V output at Hi Setting, LED1,0 are OFF. 2 – Verify that at Low Speed setting LED1,0 both ON the voltage is still sufficient to rotate the fan. Assembly code is available here.
