Re: Anyone designed a limit switch or similar to prvent pier collision

Joe Zeglinski

Hi Konstantin,

Actually, "mercury switches" are almost impossible to find, at least in
Canada, because of the ban on mercury due to it's toxicity. Perhaps some "ball
bearing" based level sensor has replaced the old mercury switches.


----- Original Message -----
From: "Poschinger Konstantin v." <KPoschinger@...>
To: <ap-gto@...>
Sent: Wednesday, July 04, 2007 3:46 AM
Subject: Re: [ap-gto] Anyone designed a limit switch or similar to prvent pier


I think it is not so important where the scope is pointed in the sky.
The failure is only happening if the scope is going to point lower
than the horizon. So what you need is a switch thats stops when the
level of the scope went under the horizon. There are mercury switches
you can use.


Konstantin v. Poschinger
Hammerichstr. 5
22605 Hamburg

Am 04.07.2007 um 01:31 schrieb Rick Wiggins:

I am trying to devise a system to prevent the AP mount from driving
the scope into the pier if the computer, etc system fails. There are
multiple failure scenerios in an observatory where various failures,
mistakes, or software features can cause the system to miss a
Meridian flip, Park command, or simply lock up and let the AP mount
merrily go about driving the scope into the pier. Usually this
causes no damage, although it certainly could not be doing any good
to the scope or the mount clutches, so I see this as a failure mode
to avoid.

I am wondering if anyone has devised something like a microswitch
which plcaed properly on the stationary section of the RA axis and a
solid object such as a rubber block or metal tab placed on the
moving section where it comes into contact exactly at the meridian
position of the mount? This would drive a relay or similar circuit
to turn off power to the mount. A fixed block works well for
permanent setups in observatories; however being able to move the
block would be even better, allow ease of portable ues, and give
settablility to the system.

I am considering such a contraption and wonder if anyone has solved
this problem or done something similar. Please let me know if you
are willing to share so that I don't re-invent the RA wheel.

Thanks, Rick

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