[amsat-bb] Re: inquiry about homebrew az-el systems

[Lizeth Norman]

Michael, Gus and the gang,
It does not matter whether we use a pot or an absolute position
encoder. They are just registers, or in the case of the encoder, port
pins.
The Arduino has libraries to use either.

The size of the motor and the size of the geartrain can be scaled.
It's really a question of what's available.

A stepper still needs some sort of position feedback..

Norm
On Thu, Feb 28, 2013 at 6:02 PM, Michael <Mat_62 at charter.net> wrote:
> This is what I was getting at when I made my earlier post about about the
> old Gemini OR-360 TV rotators.  The gear train is driven by a "540" sized
> DC motor. I can tell you from experience that one of these rotors will
> rotate a mini sized beam on HF.  I do it everyday. So if we are driving a
> smaller array, we might be able to eliminate some or all of the gearing
> involved and go with one of the smaller motors. I can't recall the issue but
> it seems to me I saw an article in QST where someone was driving a small
> little beam on top of a tripod with a small little motor.  I still think a
> position pot is a better option for pointing over a stepper motor though.
> Michael, W4HIJ
>
> On 2/27/2013 8:30 PM, Gus wrote:
>>
>> Returning to this topic...
>>
>> I'm thinking about a rotator that can handle a small system like the
>> Arrow, or the Cushcraft A270-6s or even the A270-10s.  NOT big boomers like
>> the KLM 22/40 el CP yagis!
>>
>> So we're looking at 1½ - 2 sq. ft of windloading, and maybe 10 lbs of
>> weight.  (Including some sort of crossboom, clamps, coax and counterweights.
>> Rear mounted antennas like the Arrow will need a rear-mounted
>> counterweight.)
>>
>> Anybody qualified to say what that adds up to in terms of TORQUE required
>> from the motors?  With a little extra thrown in for a safety margin, maybe?
>>
>> I think a simple, low-cost, easily reproducible design is probably doable,
>> if we combine our ingenuity and expertise.
>>
>> -- 73, de Gus 8P6SM
>> Barbados, the easternmost isle.
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>
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