Posted on May 17, 2011 at 10:17Hi, I am designing a two axis telescope drive based on steppers
and L6208. The edge conditions of this application are:
- fast positionning in rectascension (hour axis) and declination
- smooth sideral tracking (with an angular speed half as fast as
the hour pointer of a clock). Typical tracking speed is 20 to
50 half steps / second (so there should be sufficiant CPU time
left for controlling such an operation)
The idea is to provide a fast ''star-hopping/go-to'' in half steps,
while doing the sideral tracking of the hour axis in micro-stepping
mode.
After having referenced an absolute sky/home position, in the course
of a sky watching session multiple switching between those basic
modes of operation should be possible without heavy loosing/falsifying
steps/position.
The micro-controller I favourize is a 16 bit Fujitsu MB90F543 just
for the reason of being familiar with. It contains programmable
pulse outputs with might be used for PWM purposes thus replacing
two additional D/A converters for defining the rectified, 90 degree
phase shifted sine wave shapes at both V-ref inputs.
Question: is there any application existing that contains programmable
mode switching between half step/microstep driving? What aspects
like internal phasing of the L6208 have to be respected?
Many thanks in advance for your appreciated reply, Lutz
