Safe Remote Operation
Posted 20 June 2013 - 02:44 PM
Posted 20 June 2013 - 09:17 PM
Posted 21 June 2013 - 12:12 AM
Posted 21 June 2013 - 01:08 AM
If the runaway is the primary fault, I am thinking of putting an automatic power switch in the system. The power supply current during tracking should be fairly small compared to a slew or runaway current. For this a simple current monitor with a high limit is all that is needed. A bypass would be required whenever the scope needs to slew, but the monitor could be disabled any time an operator is present. Does anyone know of other conditions I should monitor to protect the scope and drives?
Posted 21 June 2013 - 01:53 AM
All modern Astro-Physics mounts are optimized for remote operation. Additionally, the Astro-Physics 1100GTO and 1600GTO mounts can be had with absolute encoders but AP mounts are not cheap.
The Software Bisque Paramounts are also optimized for remote operation but are not cheap either.
The Celestron CGE has the needed switches and is about 1/3 the cost of an AP or SB mount. That might be an option.
Some people have added limit switches to LX200GPS scopes. I don't have any links to share at the moment. You could always work up your own.
If you were to set up the LX200GPS worm block play-limit-screws so the mount axis motor would stall instead of cause the worm teeth to skip over each other, the CPU would detect the servo motor stall and stop the motor and report an error. Also set the clutches tight enough to make the motor stall instead of slip the clutch.
This problem/challenge exists regardless of the motor type involved. The cure is having some kind of absolute axis position sensing ability. Either via limit switches or better-yet, by absolute encoders.
One of the best features of the modern Astro-Physics mounts (Mach1, 900GTO, 1100GTO, 1200GTO, 1600GTO and 3600GTO) is that they keep their sky-position awareness regardless of how they were powered down. When they are powered back up, they get time from an internal real-time-clock and they know exactly where the mount was pointing when it was shut down. They have a "brownout feature" where they detect the loss of the main 12VDC power and are able to save their current axis positions to NVRAM before the power drops to zero. Pretty-darn nice feature!
I hope this helps.
Posted 21 June 2013 - 09:21 AM
I do have video in the dome so that I can see what is going on, and I do have remote power management so that I can kill the power to ths scope if it starts acting up, but I have never used it in the 6 years it has been setup.
Operating the scope remotely is a whole other deal. I use ASCOM as my LesveDome driver requires POTH to function properly. I have constant problems Parking and Unparking the scope in this configuration. Frequently I will simply use the "hand pad" in the Autostar software and then move the dome manually to where the scope is pointing.
I hope this gives you some help.
Posted 21 June 2013 - 01:50 PM
Are there any other failures other than a runaway that could cause damage?
You can shut down the system and forget to power down the mount. It will run until it bottoms out and keep running. I did that once and got away with it. Reconfigured the system power so that the mount will always power down.
You have to plan for something going wrong eventually, no matter how many people tell you they have not had a problem.
I never had a runaway until I had a runaway. In my case I can see and hear what is going on in the observatory and if all else fails I can power the entire setup down buy simply unplugging two UPS units in my house.
Setting up a remote system is easy, setting up a reliable remote system isn't.
Posted 21 June 2013 - 03:50 PM
Posted 24 June 2013 - 01:58 PM