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From: hbg6@citek.mcdphx.mot.com
Newsgroups: sci.electronics
Subject: Re:Fan for my amp revisited
Message-ID: <12472@qisoff.phx.mcd.mot.com>
Date: 26 Apr 91 15:51:52 GMT
Sender: listen@qisoff.phx.mcd.mot.com
Reply-To: hbg6@citek.mcdphx.mot.com
Organization: Motorola Microcomputer Division, Tempe, Az.
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In article <12462@qisoff.phx.mcd.mot.com> I wrote:
>>ritz@msb.com (Chris Mauritz) writes:
>>
>>> the speed of an AC fan was not as simple as adding a pot.  OK,
>>> how about I use a DC fan and siphon off power from the power supply
>
>All of the DC muffin fans I have used contain a bunch of digital control
>and analog drive circuitry ( tiny SMT parts under the cap at the non-moving
>end of the motor ).  This stuff drives a brushless DC motor and probably
>would not take kindely to much less than their rated voltage. I'll see if
>there is one in our scrap pile to 'smoke' test.
>

I found a fan around here rated for 6 -> 15 volts DC. There IS quite a
range of fan speed based on voltage. It starts to spin at around 4 volts,
moves a lot of air at 15volts, makes an interesting hovercraft or
gyroscope demonstration at about 48Vdc, and gets mad and won't play
anymore at around 65Vdc.  :-)

John