Troubleshooting guide

saying that the time for the wheel's motion to complete has expired.
The default algorithm for motion of the wheels is that they first go to the home position, tell the controller
to zero the position, and then move to the demanded position. We refer to this as a home-type of limit, or
limit switch. We usually run the MOS wheel in an alternative mode refered to as a home-type of near-
home. In this mode the wheel moves from the present position back to somewhere close to home, and
then to the demanded position.
There are two modes of failure for each wheel.
(1) The limit switch fails to engage. If the wheel operates with a limit-switch home type, then the
wheel can spin endlessly, and the perl script will just give up after some time limit. If you can stop
the wheel and determine the location of the mechanism, it is possible to recover from such a failure
and then use the near-home motion algorithm for the wheel.
(2) The wheel binds, and a grinding noise is audible if you stand next to the dewar. If this happens
there usually is no quick recovery after you have stopped the motor.
Solutions:
A) First, you must stop the wheel that is either spinning endlessly, or is jammed.
1. Type ctrl-Z, type jobs, kill -9 %<jobnumber> if the perl script has not yet finished and
you already know that there is a problem.
2. Type ufmotor -host flmn-4m-1a -port 52004
a) At the motor prompt, type <motor_name>@, where <motor_name> is one of letters a, b,
c, d, or e, where motor a = decker, b = mos, c = filter, d = lyot, and e = grism. This should do
a soft-stop of the motor.
b) Type exit to quit ufmotor.
3. Type turn.off.motor.hold.current.pl
If this does not stop the motion of the wheel (e.g., you can hear it spinning, or grinding), the last
recourse is to turn off the motor controller itself. Note: any wheels that use near-home type and
are not at home will be lost when the motor controller is powered up again. You should call for
assistance if this happens. To do cycle the power on the controller, telnet baytech as
motorpow, password ______, and then reboot 1, and logout to exit.
B) If the failure was of the limit switch, you need to recenter the mechanism in question, and
redetermine the home point. The best way to do this is to image a very bright star with the telescope out
of focus by about 3000 units. The wheel probably is not well centered, so use one of the tweak scripts
to adjust it (there are special engineering tweak scripts, in addtion to the ones for the decker and MOS
wheels). Then step the wheel by discrete positions, and measure the background. With some help you
should be able to determine where you are, and use the ufmotor command to rezero everything.
FLAMINGOS@4-m, Ver. 2.34, 2006 Apr 04 Page 36 of 44