Stamp Code

[Tom Droege <tdroege@veriomail.com>]

Today I am working on the Stamp code.  I am trying to get it set up so that 
I can keep the Declination drive motor on while I clamp it.  This should 
make it have a lot more holding torque.  This should prevent movement of 
the Declination drive after it reaches the desired position.  There will be 
a 0-3 count uncertainty in where it ends up until someone writes code to 
keep track of the stepper motor drive phase.  This is at most 12 minutes of 
arc, and probably less than the backlash.  From feel, it is at least 10x 
stiffer if the current is on, probably more, but I have no good way to 
measure it.

For newcomers, the system was designed so that one motor (of 4) could be 
driven at one time with the rest turned off.  By off I mean that the 
current drive to the motor is set to zero.  This results in low holding 
torque.  Three of the motors are used in a fashion where holding torque is 
not critical.  The fourth directly drives the Declination axis.  When it's 
current is turned off, any unbalance of the telescope can cause it to 
move.  There is a brake that clamps it in place, but that is driven by one 
of the other stepping motors.  So to turn on the brake, I currently have to 
turn off the current to the Declination drive and it moves before the brake 
is put on.  Sigh!

The result is that I will have to immerse myself in the Stamp and motor 
drive code.  So if anyone wants something else added, now it the time.

Tom Droege