Micro-motor Actuated Pneumatic Switch |
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| It was Linc Smith who first came
out with the micro-motor actuated pneumatic switch back in '98.
Thereafter, there were improvements by Brian Alano and
Ben
Williamson. |
| My thanks to Nicolai Gørtz who
provided feedback that he had followed the links to the pneumatic
switches by Linc and Brian. He had built both and found that they
didn't work. He thought both could be built with some serious changes
though and is working on an improved version of Brian's switch. |
| Well, I'm not in the position to
check out all the stuff that this site is linked to. I put the links
which I think are interesting and inspirational. However, having
recently acquired a bunch of micro-motors I decided to build these
switches and give my
opinion on all three of 'em. |
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Micro-motor actuated
pneumatic switches by Linc, Brian and Ben (gear-side view) |
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In Linc's original design, the micro-motor
is held firmly but the worm gear is only supported at one end. The 24T
gear is sort of floating with its axle at the lower end of a 1x3
liftarm. The axle is not at the pivot point of the handle of the
pneumatic switch.
Unfortunately, the switch doesn't work properly in practice. The axle of the 24T
gear gets badly twisted and the gear will jam against the housing
causing the motor to stall. |
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Brian has a more rugged and reliable version
of Linc's switch. But note that his LDraw pictures show the switch handle on
the wrong side. I got over it by building a mirror image. (It would
help if TLC had made a left- and right-handed pneumatic switches).
The worm gear is firmly held by 3-long cross blocks. The 24T gear
is supported using liftarms on both faces and the axle is at the level
of the pivot point of the switch handle.
The switch works in practice but the motor mount could be
improved. The micro-motor gets pushed outwards as it is held by only one stud at its
bottom. |
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Ben has modified Linc's switch
to hold the 24T gear more firmly but only on one face and it's not
that strong. The axle is at the level of the pivot point of the switch
handle. The micro-motor mounting is fairly firm but the worm gear is
supported at one end only.
Most importantly, Ben has added a touch sensor that can monitor the center
of the switch's throw.
The switch works in practice but the axle of the 24T gear gets twisted
a bit. I've not had occasion to
try out programming the center position monitor. |
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| Conclusions |
| The micro-motor
based pneumatic switch was conceived as a compact replacement of the
more bulky switches based on the 9v mini-motor. One of the goals is to make the bounding box of the switch as small as
possible, hence the use of the micro-motor. These switches are not by themselves very sturdy and need to
be incorporated into a more rigid structure of the model. |
| However, the price
paid for being small is slowness in actuation. All the micro-motor
based pneumatic switches take 10-14 seconds to move the switch
from one end to the other. That's a very long time considering that
the pneumatic action that is being controlled is almost
instantaneous. |
| To get the benefit
of the pneumatic pistons, they've got to be activated rather quickly,
for example, when they are required to grab at an object, else the
object would have got away. |
| I've a feeling
that the micro-motor based pneumatic switch is more of an academic
exercise. I've not actually seen them on real models, only pictures in LDraw
and Building Instructions. |
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