RE: ATM I just recieved a new Byers gear

["Antonio de Ugarte Postigo" <ugarte@mad.servicom.es>]

Dave,
    First of all, let me thank you again for your interest. I've been
thinking of what you and others have told me and at the moment my proyect
would work as follows:
    1.- Keep the synchro motor that Byers supplies for the R.A.
    2.- Look for a similar motor for the Dec axis (maybe call Byers to ask
for the motor and the reduction gears) and build a tangent arm with a
similar reduction as the R.A. gear.
    3.- Build a frecuency regulator to control the speed of the motors (I
will need someone's help to find the plans to build it)

    I would like to have the opinion of as many people as possible and any
ideas or experiences will be of great help. I would specially appreciate if
someone could send me the plans for the frecuency regulator.

    Thanks a lot to all the ATM list,

                        Antonio de Ugarte Postigo

-----Mensaje original-----
De: DROWESMI@aol.com <DROWESMI@aol.com>
Para: ugarte@mad.servicom.es <ugarte@mad.servicom.es>
Fecha: viernes 18 de diciembre de 1998 23:27
Asunto: Re: ATM I just recieved a new Byers gear


>Hi Antonio
>The problem that I see is that the synchro motor which came with the Byer's
>gear must have a built in gear head reducer.  If you use a stepper motor on
>this axis, then you will need to provide gear reduction between the stepper
>and the Byer's gear.  Assuming that the worm gear has a reduction ratio of
>360:1 (or 359:1) then to achieve 1/4 arcsecond halfsteps with a 1.8 degree
per
>step motor, you would need an additional gear reducer of approximately 9:1.
>In addition, you would need to fabricate the mechanics to couple this
reducer
>to the motor and to the Byer's gear.  This seems like unnecessary trouble
to
>me.  So, it may be better to leave this motor arrangement alone and work on
>the dec axis instead.  Since the dec axis does not have to have finely
>adjustable rate control, a stepper motor circuit using a 555 timer may
perform
>adequately.  However, if you plan on using an autoguider with this mount,
555
>clock drift would cause a small change in dec rate calibration of the
>autoguider.  This should not be a problem, just wanted you to be aware of
it.
>
>Others on the ATM list have circuit designs which use a 555 to directly
drive
>a stepper motor controller IC.  Look into this as a start, it is a much
>simpler problem that making the precision motor controller that I
developed.
>Be aware that depending on the dec tangent arm reduction ratio, you may
still
>need a reducer between the stepper and the tangent arm.  I would shoot for
1/4
>arcsecond per halfstep, maximum, for this axis also.
>
>Regards and best of luck,
>Dave Rowe.
>