Stamp Code for Dec. Drive

[Tom Droege <tdroege@veriomail.com>]

I have succeeded in rewriting the stamp code so that two motors can be on 
at the same time while only one is moved.  It works on the test stand.  It 
turned out to be relatively easy once I broke down and did the completely 
dumb thing of duplicating the move code for each motor.  It even took less 
stamp space than I expected, and I only needed a single nibble variable for 
routing.  There is still about 30% vacant code space and a byte and a half 
of unused variables.  Upgrades will be possible.

The holding torque is much larger if the motor current is on.  This should 
solve the problem of the Dec. axis moving before the brake is applied.

For those new to the list, the present Declination drive axis is 
marginal.  It used to move around a lot.  Then I added a brake that clamps 
it.  This works OK, but when the power is turned off on the Dec. drive 
stepping motor the axis will move if it is at all unbalanced.  The old 
scheme turned the current off on the drive motor before the clamp was 
turned on.  This was because the system was designed to turn on one motor 
at a time.  The new control scheme allows two motors to be energized at 
once.  This allows the Dec. motor to remain energized where it has much 
more holding torque while the clamp is applied by a second stepping motor.

All the work is not done yet.  I still have to go through the QBasic code 
and rewrite the parts that access the Dec. axis so it takes advantage of 
the current on feature.  At present I always turn the motors off after I 
move them.  So I have to find all the places I do this and do something 
else.  I hope to test all this on MIKE over the next several days.  I 
anticipate that I will have to fuss with the motor phases to get things 
right.  I tried hard to preserve the previous phase.  This means that all 
four motors will run backwards if my standard luck holds.

I think this is the last item on my list of any consequence.  What is left 
will be left to the operators.  There will be lots of little fussy things 
to make better as you all will find when you have systems.  Most will be 
peculiar to your location.  Arne does not have to worry much about 
humidity, as I do, for an example.  So I will have to rig up something to 
dry the air better than I now do it.  And so on.

I am pretty pleased.  I think I have now completed the engineering phase of 
this project.  There is production and software and data analysis, but that 
is different.

Tom Droege