Re: Fan Motor

On Mon, 21 Apr 2008 23:47:42 +0800, spamfree@xxxxxxxxxxx wrote:

Sorry for such a simple question, but I've got a few 120mm
240V .125A (?30W) axial fans like a bigger version of the case
cooling fans in a computer.

I've set one up in a box with a large truck air filter so I can run it
24/7 to remove dust from my house atmosphere. At the moment, the
aircons and computers do it :)

Unfortunately these fans are a little too energy hungry and noisy.

What are my options for slowing them down a tad?

I thought of adding a resistance in line, but this would only
dissipate heat -- not lost in Winter, but a waste of money in Summer.

Then I thought about running two of these in series.

Is there any cheap and cheerful way to cut down on these over
enthusiastic, but otherwise great little ball bearing fans?

Thanks guys. I'll look for a fan speed controller, but I guess they
usually only come cheap with fans?

I've read that a transformer would be OK.
I see a cheapie 36V that would suit.
What speed would the fan likely do (fraction of full speed) at 36V?
Perhaps around half speed, if the curve I/rpm is logarithmic?

Then someone suggested a diode in one lead. Is that liable to damage
the motor? Perhaps a tranny is safer.

I don't really need a variable speed, just roughly halve the full
rate.

Cheers, jack
.

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