[AMPS] remote coil/cap driver motors

[rb]

}}}Hello Ron,
I wonder if you could share the responses to your AMP LIST question
about driver motors for roller inductors and variable capacitors.  I
have been looking for some ideas for some time.
Thanks for your help.{{{

Matter of fact I did get some great ideas.

a.  stepper switches.  A definite possibility.  Many have shafts that are
1/4" or 3/8".  They have plenty of torque, and are reversible.  The only
down side is they lack precision.  Most steps are slightly less than 2
degrees.  Your tuning points may or may not fall exactly on a step interval.
Still, they'll get close.  Most will require a dc power supply between
6-24v.

b.  electric screwdrivers.  These too are promising.  They have the torque
and are reversible.  Speed on some isn't variable, and may be a little fast
for direct drive on a variable cap, and slow on the roller coils.  A problem
is how to contol.  Seems you would have to cut them open and take the rocker
switches out and mount in your remote unit.  They come with the ac/dc
converters-battery chargers.

c.  windshield wiper motors.  plenty of torque, and they are reversible.
Maybe a little fast on shaft rpm for direct drive.  Require 12vdc power.

d.  automotive power window driver motors.  About the same considerations as
windshielf wiper motors.  Require 12vdc power.

e.  BBQ spit motors.  Plenty of torgue, but tend to be single speed, and
many are not reversible.

f.  variable speed reversible electric drills.  Idea is to mount in brackets
and couple direct onto coil and variable cap shafts.  Plenty of torque.
Speed is controllable, and they can be chucked to many shaft sizes.  The
reversing switches and speed controllers would need to be removed and
remoted. Could use outboard solid state motor speed controllers to set max
shaft speeds if variable shaft speed not needed/desired, or ideal but
different shaft speeds could be set with two independent motor speed
controls in the remote/shack unit.

A problem still to be solved is whether or not we need to know the position
of the rolling contact on the coil, and the shaft on the variable cap.
There seem to be two schools of thought here.

1.  Don't worry about where the coil or cap is in their travels.  Simply
tune the coil for max noise in receiver, then the cap.  Once to this point,
put low power rf in and tweak the tuning.  This approach may or may not work
in all situations.

If this approach is used, the main challenge is to engineer/rig limit travel
and reversing switches on the coil and cap.  The coil part of the problem is
easier, in that micro switches can be placed on brackets at both ends of
contactor travel.  The builder should use non-conductive wands and/or cover
the micro switch arms with non-conducting material so that no shorts occur.
A crude but effective way of putting stop limits and reversing switches on
variable caps is to drill the shafts maybe an inch or so apart with small
holes, on the part behind the front panel.  Long machine screws can then be
placed in the holes, and the part sticking up can be used to activate micro
switch on brackets as the shaft rotates.  Pulse sprinkler heads use a
similar concept.  With this approach, the coil and cap will simply go from
one limit stop to the other, reverse, and duplicate the process.

2.  For those who want to know or need to know where the coil and cap are in
their travels, it becomes more difficult.  I don't have any solutions yet.
Maybe some of the guys on the reflector can provide simple means of doing
this. Getting a remote position indicator on the coil would seem to be the
bigger challenge.

I know hams have built and used remote tuners through the years.  I'll be
looking for ham mag ariticles on this topic.  The thing is, stuff available
in yesteryear may not be available today.  And, we have lots of new geegaws
that may well be adaptable to this, with some ingenuity.

73 de Ron, K5BDJ


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