Subject: Re: [sloan-25mlog 3853] 2.5m obslog 20180125 (SJD 58144)
From: John Downey
Date: Fri, 26 Jan 2018 10:48:49 -0700
Looking back at the instance of flat field problems on Dec 23/24 2017, =
it was also petal #2.
The description then was a bit less clear to me, but I would be that it =
was the same - one of the switches stuck, confusing the MCP and PLC as =
to the state of the petal.
These switches are readily available for $14, I believe we will just =
replace them all as it does not look too difficult to do.  I only have =
three spares on hand, so I will probably replace the ones in #2 today, =
then do the rest during engineering next week or the following month.
> On Jan 26, 2018, at 10:00 AM, John Downey  =
wrote:
>=20
>=20
>> Plate 8201 is not complete.
>> 13:10Z  We had some trouble moving the telescope to 5 degrees for =
closing. The
>> goTo5 script was stating that the telescope "did not decelerate" and =
stopped at
>> alt=3D5.5 degrees.  We deemed it unsafe to move the enclosure and =
tried moving the
>> telescope back to stow and back to 5 degrees.  We noticed that the #2 =
flat field
>> petal was reporting in the MCP window as in a confused state, ie "?". =
 Checking
>> the interlocks for that petal, the interlock stated that Petal #2 was =
still
>> open. Visual inspection show that the petal was flush against the =
telescope and
>> closed.
>>=20
>> Solution:  Open the panel and set to manual mode for the flat field =
petals.  We
>> opened and closed Petal #2.  The sensor then read that all the flat =
field petals
>> were closed.
>>=20
>> Re-issued to the command to goTo5 using the script.  Success and we =
have now closed.
>>=20
>> Can someone check the sensor to Petal #2, as well as the motor and =
belt?  Upon
>> visual inspection, the belt looked ok.  With auto-close of the =
petals, the MCP
>> was reporting a confused and/or state for this petal, even though it =
looked like
>> it was closed. =20
>=20
> Good job figuring it out, cycling the petal manually is the first =
thing to try.
>=20
> The way the system works, the open and closed limit switches also act =
as the open and closed sensors.  Given the problem and the means by =
which it was corrected, I suspect that the mechanical switch for "open" =
had stuck and the act of manually moving the petal from closed to open =
caused it to unstick.
>=20
> Probably we need to look at replacing all the switches - they have =
been in use about 4 years now with some exposure to dust and moisture, =
probably we're starting to see the limit of their maintenance free =
lifespans.
>=20
> If its easy to do I'll order switches and take care of it during an =
engineering week, if it requires a great deal of disassembly it will go =
on next summer's list.
>=20
>=20
> ____________________________________________________________
> Logs of Nightly APO Activities
> =
https://trac.sdss.org/tracmailman/browser/private/sloan-25mlog/index.html