
Originally Posted by
Harold14370
What you are trying to do is to control the power to the fan by turning it on and off, with the power to the fan being on for 15 percent of the time. Naturally, this causes the fan to continually stop and start, hence the noise. When you put a capacitor in parallel with the fan, you are smoothing out the voltage, but you are also defeating the purpose. The fan will draw the same amount of power during the "on" cycle as it did before the capacitor, then it will draw additional power from the capacitor as the capacitor discharges during the "off" cycle. When the capacitor is charging up, the current could be rather high. It is only limited by the internal resistance of the power supply. By turning the capacitor on and off, you could be putting a lot of voltage stress on your power supply. I'd try to find a different way to do it.