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Power for Observatory

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#1 mshetzer

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Posted 21 May 2021 - 02:43 PM

I am in process of putting together an observatory (Sirius Dome) 100 feet from my home.  I will be running an extension cord for a while for power, and wondering if others use a UPS or similar to ensure again power outages, etc.

 

I have a few components that only run 12v (like the Dome rotation), and I am curious what others use to convert to this voltage.

 

The following will need power.

  1. MyT Mount
  2. MaxDome 
  3. Computer (NUC)
  4. Monitor
  5. Pegagus Ultimate Power
  6. 2 Cameras and Filter wheel

 

Thanks in advance for your thoughts !

 

Matt



#2 Couder

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Posted 21 May 2021 - 03:39 PM

I've kind of been planning ahead. I found large power supplies with 6, 12, and 24 volts filtered output. These are new ones for camera systems, such as a large setup in a department store. Many outputs. I've also got some from telephone systems, also filtered. But they are heavy.



#3 PGW Steve

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Posted 22 May 2021 - 03:39 AM

In one of my domes I run four 120ah batteries and have everything running off that, and have the batteries charging via 120v off a nearby cabin. I have a solar panel and charge controller I plan to add this summer. I have had breakers trip before and shut the obs down and like the stability of having it run this way. I want to convert my other observatory/imaging rig to the same system as well.  



#4 kathyastro

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Posted 22 May 2021 - 06:48 AM

I have a buried cable for my electricity.  I have several 12v power supplies for various functions.  An old 8A power supply that I picked up for $10 at a junk shop powers the dome shutter motor.  A separate 5A power supply runs the dome rotation motor.  A 30A regulated power supply supplies power at the pier for the mount, camera, filter wheel, focuser, etc. I use Powerpole connectors for all 12 volt connections, and a RigRunner at the pier for the various devices.

 

I do have a UPS for the computer, mostly for its regulatory properties.  It will power the computer for 15 minutes in a power failure, but that won't do me much good on an all-night session when I am asleep. 

 

More important is the battery backup for the shutter and rotation systems.  It consists of a 65Ah marine battery (my star party battery), which I keep connected to a smart charger.  Its output is connected via diodes to the outputs of the rotation and shutter power supplies, so it can power both systems in the event of a power failure.  It also powers the Arduino that controls the dome.  In the event of a power failure, the Arduino will not wait for instructions from the computer.  It will autonomously park the dome and close the shutter.



#5 rpineau

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Posted 22 May 2021 - 01:51 PM

I have an electrician run 110V 16A to the observatory from the house main so it's on its own breaker. It's about 30 meters from the main panel to the observatory (goes through the house crawl space, exit on the side of the house and goes underground to the observatory for about 8 meters).

In the observatory I have a 1500 VA UPS. This then power the mount (PMX+), NUC (running Linux), Digital logger web PDU, dome controller and a 12V 30A PowerWerx supply ( https://powerwerx.co...upply-powerpole )  that feed 12V (actually 14.1V but all equipment is rated to move that 15V) to the rest of the devices (via a rigrunner).

I like the UPS to prevent issues on short power outage or brownout, and I get a SMS and an email if the UPS battery goes bellow 10% so I can properly shutdown everything (the most important being closing the dome and parking the dome to the charging pads). I need to add more automation so that the whole shutting down doesn't require me to remote into the NUCn to park the mount and dome (work in progress).

 

Rodolphe


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#6 archer1960

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Posted 22 May 2021 - 03:35 PM

I have a 60A 12V regulated power supply (set to 13.2V) that easily powers my entire rig. If I were using it to also drive the dome (which I don't right now), I would probably sequence things so that the rig wasn't powered up until the dome is positioned and the shutter open, in order to minimize transients on the 12 power.



#7 kathyastro

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Posted 22 May 2021 - 04:21 PM

I have a 60A 12V regulated power supply (set to 13.2V) that easily powers my entire rig. If I were using it to also drive the dome (which I don't right now), I would probably sequence things so that the rig wasn't powered up until the dome is positioned and the shutter open, in order to minimize transients on the 12 power.

The dome has to track with the scope, so you don't have the luxury of powering the rig or the dome but not both.  At times, you will need both.

 

I minimize transients by using separate power supplies, and by wiring in snubbing capacitors in my power controller.



#8 archer1960

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Posted 22 May 2021 - 05:15 PM

The dome has to track with the scope, so you don't have the luxury of powering the rig or the dome but not both.  At times, you will need both.

 

I minimize transients by using separate power supplies, and by wiring in snubbing capacitors in my power controller.

Yes, I know, but the shutter generally won't need to be moved, and ongoing azimuth adjustments are small, rather than (potentially) having a long run for initial positioning.

 

How much current do your dome motors pull?


Edited by archer1960, 22 May 2021 - 05:16 PM.


#9 kathyastro

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Posted 22 May 2021 - 05:51 PM

Yes, I know, but the shutter generally won't need to be moved, and ongoing azimuth adjustments are small, rather than (potentially) having a long run for initial positioning.

 

How much current do your dome motors pull?

The shutter motors run on DC.  The upper door motor runs off an 8 amp power supply, and it doesn't blow the fuse.  The maufacturer's spec sheet says 7.2 amps at 135 inch-lbs torque.  I know it runs well below that torque, because the shutter cable will snap at 90 inch-lbs. (Ask me how I know!)  So probably 3-4 amps, maybe even less

 

The rotation motor is a stepper, which runs off a 5 amp power supply, again without blowing the fuse.  It is harder to measure the current draw of a stepper.  It ramps up in speed when it starts, so it avoids the hard start of a DC motor.  Less transients that way, which is good since it has to operate during the session.

 

Transients happen during starting and stopping.  A long run will only have two transients, whereas the micro-slews of tracking will cause two every few minutes. 


Edited by kathyastro, 22 May 2021 - 05:54 PM.


#10 archer1960

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Posted 22 May 2021 - 08:30 PM

The shutter motors run on DC.  The upper door motor runs off an 8 amp power supply, and it doesn't blow the fuse.  The maufacturer's spec sheet says 7.2 amps at 135 inch-lbs torque.  I know it runs well below that torque, because the shutter cable will snap at 90 inch-lbs. (Ask me how I know!)  So probably 3-4 amps, maybe even less

 

The rotation motor is a stepper, which runs off a 5 amp power supply, again without blowing the fuse.  It is harder to measure the current draw of a stepper.  It ramps up in speed when it starts, so it avoids the hard start of a DC motor.  Less transients that way, which is good since it has to operate during the session.

 

Transients happen during starting and stopping.  A long run will only have two transients, whereas the micro-slews of tracking will cause two every few minutes. 

Thanks for the data. It sounds like my 60A power supply would likely handle it with no trouble, even with the start/stop transients. I guess I could hang a couple of good-sized caps off the output to filter it if necessary.

 



#11 Raginar

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Posted 02 June 2021 - 03:00 PM

I am in process of putting together an observatory (Sirius Dome) 100 feet from my home. I will be running an extension cord for a while for power, and wondering if others use a UPS or similar to ensure again power outages, etc.

I have a few components that only run 12v (like the Dome rotation), and I am curious what others use to convert to this voltage.

The following will need power.

  • MyT Mount
  • MaxDome
  • Computer (NUC)
  • Monitor
  • Pegagus Ultimate Power
  • 2 Cameras and Filter wheel

Thanks in advance for your thoughts !

Matt

I dunno what your soul type is but that’s a pretty short run. In Florida (Sandy) I could dig and slide the cable in the ground. In South Dakota, it was definitely more challenging but tolerable. A single 15-A circuit is enough.

See if you can find an electrician that’ll let you do the digging if you’re uncomfortable with electrical code.

#12 GrandadCast

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Posted 03 June 2021 - 07:51 AM

The run from our power transformer pole to the observatory is 250 feet through rock. So the electrician used a rock trencher and ran 240AC 60 amps. These gives the observatory plenty of power for air conditioning and other needs. Several 12volt supplies 15 amp, 30 amp and I use the power supply that can with my mount. The Aleko roof is using a 120 volt motor so I haven’t added any battery and inverter backup for that yet. Just plain UPS computer backup. Haven’t had any issues with power outage except our freeze this year. I control all my scope power, computer, monitor, lights, webcam, and several outlets with an internet power remote system using an iPhone. 

 

Jess


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#13 Raginar

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Posted 03 June 2021 - 07:20 PM

Jess,

I ran my genie garage door opener off a 1500va battery backup. It could run it a few times before it killed the batteries.
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#14 kpem

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Posted 04 June 2021 - 09:20 PM

If you're in an area that sees a lot of lightning, and if you're not running remotely, you might consider putting in a service disconnect on the observatory side of the run to prevent things being blown up from the induced transients of a nearby strike. I have a 75 ft. run from house to observatory and have had a UPS killed by a nearby strike. The UPS did its job as a transient suppressor and protected the equipment in the observatory, but it was totally fried. You would have to shut down the UPS, of course, until you reconnect. And check your local codes to see if that's allowed.



#15 MJB87

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Posted 05 June 2021 - 07:08 AM

I second the above post. Same thing. Ground strike came up my Ethernet cable and burned out my LAN switch in the observatory. Fortunately, the switch's sacrifice saved all of the ancillary items connected. (The mount breaker is always disconnected except when I'm using it.)

 

Invest in a good surge protector for both electrical AND data connections. Better yet, switch out the Ethernet cable for fiber.


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