Developers guide

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pushing the mount in the opposite direction to which it is travelling. Note that this motion will not
be recorded by the software, which only monitors the encoders attached to the motor shafts.
In order to compensate for this slack space, the anti-backlash motor, show in Figure 2-7, provides
a constant tension in one direction, forcing the worm gear to remain in contact with one side of
the main gear, eliminating any free movement of the telescope mount.
Figure 2-7 Anti backlash motor
For this reason, during normal operation of the telescope, the anti backlash motor should always
be powered on.
2.6.2 Limit switches
Limit switches are used in order to prevent the telescope from damaging either itself or any other
equipment in the enclosure by travelling too far.
Four switches are used for each axis:
• 2 inner limits
These provide digital inputs to the Macrostation. When triggered, the software is notified
via the PMAC (see 2.6.4) device driver should take measures to stop the telescope
moving further.
• 2 outer limits
Triggering the outer limits will cause the corresponding servo amplifier to cut power to the
servos, preventing the telescope from moving.
The Inner (software) limits restrict the range of the declination axis from -75º to 29º55’, and the
right ascension axis to approximately 4.5 hours either side of the meridian.