You'll need to look at the back of one of the fans. The pwm signal is strong enough to be split upto 10x, so hubs are not an issue, generally being 6-8 fans. Because pwm fans always run 12v, the motor isn't as heavy duty, it's not required to use higher amperage to make up the difference in wattage at 5v or 7v, so can run as low as 0.18A each, or 3-4 fans per splitter. A DC 3pin fan will usually run 4-6w each (0.3A-0.5A), so general recommendations put no more than 2 splittered DC fans per header. These controllers are almost always mounted in an optical bay, and can be led or analog or a mix, so enabling auto or manual control of each header.Įach motherboard header is ostensibly rated at 1A, that's just 12w at 12v. Your basic hub is nothing more than a hard splitter that's generally powered by molex or Sata and is always pwm.ĭC 3pin fans require an actual controller, as it'll need rheostats to change the input voltages. Consequently, pwm fans can drop as low as 20% duty cycle, or 200rpm on a 1000rpm fan.īecause of these differences in voltage use, the 2 kinds of fans don't mix, and neither do hubs unless you go all out for a seriously expensive powered and software controlled hub. They use a pulsed signal to turn the fan motor on/off, but remain at a constant 12v. So a 1000rpm max fan will spin at 400 or 600rpm low and 1000rpm high.Ĥ pin fans are digital. Because there's a need for a certain amount of voltage to actually turn the motor, this ends up as 40% or 60% to 100% duty cycle in bios.
They are directly controlled by the voltage applied and normally that's either 5v or 7v low to 12v high.
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