upIn my experience with 12V fans, a series resistor works nicely, as doesrunning them from a stiff 6V supply.Unless you have something unusual, these fans do vary RPM in response topower supply voltage.You will have to determine the resistor by trial and error, since the fansdo not respond linearly to voltage.

They're 5V fans.A series resistor generates heat, diodes drop voltage and run cooler.. Theycan be soldered into the fan leads then covered with heatshrink sleeving. A6V supply will speed these fans up.Silicon diodes in series allow small increments and an easier way to selectthe required speed.BTW, you replied to my post, I did not post the query :-) Maybe your newsservice isn't showing all the posts?Dave

Re: Reduce power draw on a fan ? (or, speed control) ?

Jul 29, 2003 21 Replies

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Dave D 22 years ago

Try using the LM317 to drive a pass transistor capable of passing the required current. Mind, the LM317 is more than capable of supplying the

200mA you say your fan requires!

Dave

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Dave D 22 years ago

Alternatively the TL431 adjustable zener driving a pass transistor. (The TL

431- aren't they a great little device ;-))

Dave

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