multi year continuous operation steppers - low volts/zero torque

My latest research project requires a thin wire to be waved back and forth (somewhat like a metronome) through an angle that I wish to vary
crudely - the resolution of almost any stepper would be fine (alright I confess this is marginally a robotics project). This is a zero torque application and a wide range of fast or slow steppers would probably do (each wave should take about 2 seconds with a pause to fill in time on each side). Power needs to be minimized (a watt or less) and cost and complexity should be low (there will be many) and the MTBF should be years of continuous operation.
Apparently many steppers can be operated directly from logic chips in a low torque application - ie at much lower than spec voltages (eg 5 instead of 17) and much lower current bringing the power consumption down to the desired 1 watt range. (see for example http://www.techlib.com/electronics/stepper.html ) This would be a simple inexpensive solution (using surplus steppers) but I worry that it would stop working after a while - I have lots of experience with DC fans that operate at lower voltages and lower speeds - but only for a few weeks after which they require a higher voltage.
Does anyone have personal experience with any stepper that ran continuously for years?
I initially thought there must be useful steppers for this purpose inside battery powered wall clocks, but when I took mine apart I discovered that it is just 1 chip 1 crystal 1 coil, 1 pm rotor and lots of gears (no wonder it didn't keep great time).
Thanks so much for any thoughts. Best wishes, Mark http://homepage.mac.com/mkstowegnv/bbs.htm
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I would try and eliminate rotating bearings, as they always seem to cause trouble. I'd go for something like a small electromagnet attracting a flexi hinged armature. Vary the angle by varying (pulse modulation of current) the attraction. There are devices somewhat like this used in those big changeable signs.
Dave

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If you can accept the power consumption, Nitinol wires might be useful.
The steppers from floppy drives might be a more promising source of motors.
                John Nagle
Mark wrote:

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X-No-Archive: yes
: If you can accept the power consumption, Nitinol wires : might be useful. : The steppers from floppy drives might be a more promising : source of motors. : John Nagle : : Mark wrote: : : > My latest research project requires a thin wire to be waved back and : > forth (somewhat like a metronome) through an angle that I wish to vary : > crudely - the resolution of almost any stepper would be fine (alright : > I confess this is marginally a robotics project). This is a zero : > torque application and a wide range of fast or slow steppers would : > probably do (each wave should take about 2 seconds with a pause to : > fill in time on each side). Power needs to be minimized (a watt or : > less) and cost and complexity should be low (there will be many) and : > the MTBF should be years of continuous operation. : > : > Apparently many steppers can be operated directly from logic chips in : > a low torque application - ie at much lower than spec voltages (eg 5 : > instead of 17) and much lower current bringing the power consumption : > down to the desired 1 watt range. (see for example : > http://www.techlib.com/electronics/stepper.html ) This would be a : > simple inexpensive solution (using surplus steppers) but I worry that : > it would stop working after a while - I have lots of experience with : > DC fans that operate at lower voltages and lower speeds - but only for : > a few weeks after which they require a higher voltage. : > : > Does anyone have personal experience with any stepper that ran : > continuously for years? : > : > I initially thought there must be useful steppers for this purpose : > inside battery powered wall clocks, but when I took mine apart I : > discovered that it is just 1 chip 1 crystal 1 coil, 1 pm rotor and : > lots of gears (no wonder it didn't keep great time). : > : > Thanks so much for any thoughts. Best wishes, Mark : > http://homepage.mac.com/mkstowegnv/bbs.htm
Actually that is what a motor is. A metal piece, and a coil (or coils) arranged for converting electrical energy to mechanical.
Generally simple is better, and depending on how much force you need, a simple solenoid would be a good long life way to go!
That
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