[Discussion] question about fans

[Richard]

Measure the speed of it.

If there is a 4th wire like most new fans have that is to control the speed
of it rather than just doing PWM on the power which can result in lousy
spinup and speed fluctuations on the fan.

> -----Original Message-----
> From: discussion-bounces at creativespace.org.nz [mailto:discussion-
> bounces at creativespace.org.nz] On Behalf Of Robert Carter
> Sent: Friday, 3 December 2010 8:00 a.m.
> To: discussion at creativespace.org.nz
> Subject: [Discussion] question about fans
> 
> A 12V DC fan sometimes has three wires. A 9V battery on the red and
> black makes it go. What would the other wire be for?
> 
> Rob
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