Electronics reducing volts to fan

Whats the best way of reducing the voltage to fan without using a rheostat . I know about the 7volt thing , but iam just wondering fi there is any better ways .

Thx for nay help

 

Reostats use variable resistors in some form, you can of course just used fixed value resistors to reduce the voltage to a certain level, or swap the wires round to give a constant 5volts, not 12

 

Your choices are,

(a) Resistive (either fixed or variable eg rheostat)

(b) Diode junctions - waste 0.75v per diode

(c) Linear regulation - a partly-on transistor wastes some volts

(d) Pulse-Width-Modulation - switch the supply on & off so fast the fan can't catch its breath

(e) Switched-mode power supply - DC-DC conversion, a sledge-hammer to crack a nut perhaps

<pimp>
Some circuits at Fan Noise Solutions and in several Bit-Tech articles.
</pimp>

 

I understand a and b choices , but the other 3 iam not sure about . Thought after reading ur website iam going for choice b .

Thx for the help

sj