I wanted to solve the control of my radiator fans, i just want a fixed speed but not full speed. So i bought a 10 port fan hub (very cheap ~2 usd used), but that was a pwm type and my fans are 3 pin dc type, motherboard cant control it. (wasted money)
So the only way to control them by reducing the voltage (or buy an expensive dc hub).
Still there are ways to control the fans: I can connect them to the 5v directly and switch to 12v if needed (mostly never needed because the cooling is way overbuilt.) But 12v loud.
I dont want to use the 7v (12v-5v lines) that is not ATX standard.
So i bought a DC-DC step down circuit with voltage display. (~4 usd) With that i can select the fans voltage in very precise steps. So in the colder seasons i set the fans to 6v, in summer i can set it to higher. 3A max so the parts are not even warm with the 9x 0.16A Fans.
I hacked a molex to sata cable for the dc-dc and to power the 10 port hub.
Extra feature is to display the psu 12v rail voltage, not just the dc-dc out voltage. So i can monitor the 12v rail if needed.
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