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Old May 29th 06, 08:27 PM posted to rec.radio.amateur.antenna
Dave Platt
 
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Default Motor for remote controlled tuner

I'm considering building a remote controlled balanced tuner. Some type
of low RPM motor 12V reversable motor is what I have in mind to accomplish
the tuning. I will have two fairly hefty variable caps to turn along with
a moderatly sized roller inductor.


What you're probably going to want is a gearhead motor, with a
relatively low RPM rating (1 - 4 RPM is probably the right sort of
range). These have plenty of torque, and you can probably slow down
the rotation even further by using a lower DC voltage or by pulse-width
modulating a 12 VDC drive.

It'd be worth checking out a 24 VDC gearhead motor - it would run at a
slow speed on 12 VDC but might well have plenty of torque to rotate a
cap or inductor.

You'll need some sort of external limit-switch arrangement (e.g.
lever-type microswitches with bypass diodes) to cut off the drive
current when the inductor reaches the end of its range - gearhead
motors have more than enough torque to drive the inductor into its
stops and damage it.

Can anyone here recommend a particular type motor, and a reasonable
source for the the type of motors I need? Tnx.


Check the various surplus outfits on-line: All Electronics, Ocean
State Electronics, Electronics Goldmine, etc.. Going prices for DC
gearhead motors seem to be in the $10-$15 range. Goldmine has some
small gearhead motors (3 RPM at 6 volts) for $12, which might do the
job.

Also, check local surplus-machinery stores if there are any in your
area, and local hamfests/swapmeets. I picked up a bunch of 24 VDC
gearhead motors for a buck apiece at one of the latter.

--
Dave Platt AE6EO
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