Re: ARNE's drive

[Tom Droege <tdroege@veriomail.com>]

It is just great to see some calibrations coming from ARNE.  I note that 
Arne has already taken a lot of data with ARNE.  I am encouraged by the 
photometry taken on an evening with some clouds.  It sort of makes all the 
work worth while.

There is a mechanical problem.  As you all know, I put a clamp on the Dec. 
drive to stiffen it up.  The problem is that the way I have written the 
STAMP code, I can only run one motor at a time.  The hardware allows any 
combination of motors on and motors moving, it is just code that is needed 
to make it happen.

As I have written the code, I unclamp the Dec. drive, then I turn off the 
clamp motor and turn on the Dec. motor.   Since the Dec. motor is unpowered 
when the clamp is taken off it can move from any unbalance.  Then I turn on 
the Dec. motor and it stiffens up.  It is then moved to a new position and 
the current turned off.  At this point the torque goes way down.  If it was 
fighting some unbalance, or stiffness of the cables it can move.  Now I put 
on the clamp and it is fixed.

What is needed it to first power up the Dec. drive motor and then take off 
the clamp.  Then move the Dec. motor and put the clamp back on before the 
Dec. drive current is turned off.  Unfortunately the way I have written the 
stamp code, if two motors have their current on, then two motors 
move.  This can be fixed, but it takes some work.

A long story to get to the question.  Does someone want to take on the job 
of rewriting the Stamp code in a workman like way?  While the stamp is 
small, this is not a small job (I think).  The biggest problem is 
understanding how everything works.  I will have to send the person who 
volunteers a drawing set and I would expect to hand hold a lot.  The best 
person would be Chris, but I suspect he is busy as we have not heard much 
from him.  He has a complete test set up and could test as he 
writes.  Anyone else will have to send me or Chris or Arne code to check.

Tom Droege


At 01:50 PM 9/14/00 -0700, you wrote:
>A couple of additional interesting plots:
>ftp://ftp.nofs.navy.mil/pub/outgoing/aah/tass/dec.gif
>shows the change in declination (X) centroid position of
>the star BP Vul as a function of time (frame number).
>You can see that the pole of the mount does not point
>to the NCP, as you get a nice variation in the position
>as the drive passes through the meridian.
>Likewise,
>ftp://ftp.nofs.navy.mil/pub/outgoing/aah/tass/ra.gif
>shows the variation in Right Ascension (Y) centroid.
>This is a linear change, probably indicative mostly
>of drive tracking rate error.  Still, pretty smooth,
>so the tangent arm works well over a 2.5hr interval.
>   Now, how far do I have to move the mount to get
>it aligned?
>Arne