This repository contains the hardware design files (for use with KiCad) that will create a PWM controller board. The intent here is to plug this in between a motherboard 4-pin fan header and a powered fan splitter, like the Silverstone CPF04 or Swiftech 8W-PWM-SPL-ST. The pwm signal is generated by the 555 timer on the board and adjusted with the on pcb potentiometer, 12v fan power from the motherboard is used solely for the DC/DC converter and 555 timer. No power pins are connected on the output fan header.
A write up documenting this project's development can be found here: