Re: Three wired DC Motor question.
From: Asimov (Asimov_at_-removethis-bbs.juxtaposition.dynip.com)
Date: 09/15/04
- Next message: Eugen T: "Re: another mitsubishi tv post"
- Previous message: me: "Re: Monitor Problem"
- In reply to: PaPaPeng: "Re: Three wired DC Motor question."
- Next in thread: James Sweet: "Re: Three wired DC Motor question."
- Messages sorted by: [ date ] [ thread ]
Date: Tuesday, 14 Sep 2004 23:10:54 -500
"PaPaPeng" bravely wrote to "All" (14 Sep 04 20:38:15)
--- on the heady topic of "Re: Three wired DC Motor question."
Pa> From: PaPaPeng <papapeng@yahoo.com>
Pa> On Tue, 14 Sep 2004 11:37:08 -0500, "jakdedert"
Pa> <jdedert@bellsouth.net> wrote:
>Most CPU fans these days have three wires...one, I guess would be common,
>and the other two: + and feedback.
>
Pa> Now that you mentioned it CPU fans are brushless. I did wonder how it
Pa> managed to rotate without the brushes you would find in any ordinary
Pa> motor. OK the 60Hz AC supply was a quick if uninteresting answer. But
Pa> because its such a cheap item and there is little else one could use
Pa> the motor for - too weak, too slow and the fan is molded into the
Pa> rotator unit - I never cared to find out how it worked not that I knew
Pa> brushless motors was a new technology anyway (circa the 1980s.) But
Pa> then again I did wonder why a simple motor fan would cost several tens
Pa> of bucks back then and still cost more than brushed motors even now.
Brushless DC motors are a mystery until weu take one apart to find one
or more Hall Effect Switches. Indeed these sense the magnetic field
polarity reversal as the doughnut magnet in the rotor fan rotates. The
logic signal they output is applied to control the commutating
transistors which drive the opposing phase windings. It is a very simple
and rugged circuit but rather low in torque. I think the low torque
problem is because there is still a lot of energy left in the opposite
winding. I guess the size could be scaled up though.
A*s*i*m*o*v
... That was a fascinating period of time for electronics
- Next message: Eugen T: "Re: another mitsubishi tv post"
- Previous message: me: "Re: Monitor Problem"
- In reply to: PaPaPeng: "Re: Three wired DC Motor question."
- Next in thread: James Sweet: "Re: Three wired DC Motor question."
- Messages sorted by: [ date ] [ thread ]
Relevant Pages
|
