[TowerTalk] Tower mast..

[Jim Lux]

At 05:09 PM 9/18/2006, Merlin-7 KI4ILB wrote:
>I was thinking that a power window motor off of most any car would make a
>great driver for the rotor. I would just need to find or make the matching
>gear for the mast.
>  I could also use small SPST momentary contact switches on a the outside of
>a cog,  wired to leds to indicate direction ( I have hundreds of leds and
>about 30 of so small SPST's on hand.)

Magnets and reed switches are your friend.. no moving parts to get gunked up.

You can either do an incremental encoder (2 switches, one that closes 
at "zero", the other that closes every 15 or 30 degrees) or an 
absolute encoder: 4 switches, lots of magnets, use a 4 bit gray 
code.  You can also use multiple switches in parallel and one magnet, 
but usually, magnets are cheaper than switches.


>  I would just have to make me a ring of led's in the shack and wire them to
>the proper LED in the compass ring.
>  I also have some multi lead cable (there has to be 50 wires in this cable
>that I picked up at an auction, it was in a crate I bought for $5)
>  To tell the truth, it sounds like a fun project.
>   The only hard part that I can think of is the gear for the mast pole.

For the drive?  Wrap a cable around the mast half a dozen times and 
then run that to a pulley on your drive motor.  If it slips a bit, 
who cares, you've got feedback from your encoder.  You can stake the 
cable to the mast (a bit of epoxy works wonders at eliminating 
slip).. Or, you can wrap the mast in a piece of innertube.

If you want something much more burly, look for a differential from a 
wrecked vehicle.  They're used all the time in horse hot walkers for instance.
  Ideas?
>  Joe
>  KI4ILB