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Sat Aug 06, 2011 12:26 pm
On Fri, 5 Aug 2011 09:26:40 -0700 (PDT), BobG <bobgardner_at_aol.com>
wrote:
Quote:
On Aug 1, 8:20 am, default wrote:
I've got a junked Ford auto instrument panel. It has 6 actuators for
the tach, speed, fuel, etc. Identical 1" X 1-1/8" X 1/2" white
plastic modules with four wires. Inside is a little (for lack of a
better word) geared down stepper motor.
It might be a bipolar stepper except the two identical 170 ohm coils
have a common third pole (in the magnetic circuit). The coils are set
in a 90 degree "V" configuration. Three double gears to turn the
(1/16" X 1/2") output shaft.
It is very easy to take apart and reassemble. .
The rotor appears to be a permanent magnet type with at least four
(probably more like
poles. Rotation is limited to 270 degrees with
a mechanical stop on the output shaft's gear.
Anyone know how they work and what it takes to drive one?
Search for 'aircore motor'. Put sin on one coil and cos on another
from a dac to drive it.
I've got a junked Ford auto instrument panel. It has 6 actuators for
the tach, speed, fuel, etc. Identical 1" X 1-1/8" X 1/2" white
plastic modules with four wires. Inside is a little (for lack of a
better word) geared down stepper motor.
It might be a bipolar stepper except the two identical 170 ohm coils
have a common third pole (in the magnetic circuit). The coils are set
in a 90 degree "V" configuration. Three double gears to turn the
(1/16" X 1/2") output shaft.
It is very easy to take apart and reassemble. .
The rotor appears to be a permanent magnet type with at least four
(probably more like
poles. Rotation is limited to 270 degrees with
a mechanical stop on the output shaft's gear.
Anyone know how they work and what it takes to drive one?
Search for 'aircore motor'. Put sin on one coil and cos on another
from a dac to drive it.
I ruled that out already - the 90 degree coil arrangement suggested it
and I remember a national IC designed just for the purpose. The
beauty of sin/cos is absolute position information - no need for
feedback to tell you where the pointer is. But the use of iron poles
and magnetic rotor means it "cogs" (favors some angles and wouldn't be
linear) then the >100:1 gear ratio would seem to render the absolute
position advantage moot.
This is Detroit electronics - they evolve their current systems and
adapt them to existing systems - so they aren't replacing their
current stock of parts. Adaptive engineering, versus design
engineering.
That is to say, it may not make a lot of sense, from an elegance of
design perspective.
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