Project: observatory – Wiring


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We will wire the observatory for electricity with regular Romex cable, switches, and receptacles, but connect it to house power with a heavy-duty extension cord plugged into a GFCI receptacle on a nearby post. The power cord will be buried in plastic conduit, and hard-wired to the observatory wiring in a junction box attached to the bottom of the floor joists.

The post also has two CAT-5 cables for Ethernet connectivity to the home network. The second cable, originally intended for telephone service, will be reserved as a backup Ethernet cable.

 

March 5, 2018 – Wiring conduit laid

Yesterday Mike dug a 10-foot 6"-deep trench to the observatory from a 4x4 post holding electricity, water, and Ethernet. Today he laid ½" PVC conduit from the post to the building.

This task was complicated by the need to connect the in-ground conduit to fixed points on the observatory. Also, one goal was to eliminate a 1¼" Ethernet conduit and weather head sticking out of the ground next to the 4x4 post – we didn't want a second weather head with two loops of CAT5 cable between them.

Mike cut off the 1¼" conduit, and used various elbows and bushings to attach the ½" conduit to it. He had to feed the two CAT5 cables through each elbow and bushing individually bdfore cementing them together. Here's a photo of the result. The entire assembly will be buried.

For power, the observatory will plug into a GFCI receptacle on the nearby 4x4 post. This has changed. See the March 9 update below. A second length of ½" conduit will hold a 14-gauge cable. The observatory end of this conduit has an elbow, a short length of conduit up, and a second elbow to a PVC junction box screwed to the bottom of a floor joist.

Ultimately Mike will run three lengths of ½" conduit from this box to two walls and the concrete pier. 12-gauge Romex will run through the conduit to feed power to receptacles at these locations.

Here is the result of today's work. in the foreground, the power conduit's weather head is just above the ground, with the red cable on the ground. in the distance, the vertical conduit holds the two Ethernet cables. The slanted conduit holds the power cable. The trench is backfilled.

 

March 6, 2018 – More conduit

Before the rain began, Mike installed conduit from the central junction box to the middle of the west wall and the northeast corner of the east wall. This photo shows the box with two branch conduits.

 

March 9, 2018 – Change of plans

Originally we planned to supply power to the observatory by plugging a 14-gauge extension cord into a receptacle on a 4x4 post. But wiser heads prevailed, so Mike decided to replace the receptacle with a weatherproof breaker box grounded to an 8-foot rod driven into the earth.

The concern was that a short-circuit would not trip the breaker in the main electrical panel 300 feet away in the house basement. With the local breaker box, we feel confident the observatory is protected.

 

March 10, 2018 – Breaker box wired

Today Mike extended the conduit from the junction box under the observatory floor to the breaker box, then pulled 12-gauge Romex through it, and connected the wires to the appropriate points in the box. This photo was taken before the wires were connected and the trench backfilled.

Mike also ran conduit and pulled Romex from the west wall to the pier. A non-GFCI receptacle will be mounted on a 2x4 projecting from the pier's square hole in the floor, and wired to the west wall box with a GFCI receptacle.

 

March 13, 2018 – Wiring progress

Yesterday Mike drove an 8-foot ground rod into the earth, and today he connected the ground wire from the breaker box to it. He installed the breaker, fastened the cover, and called this task complete.

Next, Mike pulled Romex cable through the conduits from the central junction box to the east and west walls, then he installed plastic electrical boxes. The wiring is complete and ready for the receptacles and switches to be connected and installed.

 

March 24, 2018 – Wiring complete

When not interrupted by rain or snow over the past nine days, Mike finished wiring the observatory. He installed all receptacles and switches, and connected the branchs together in the junction box under the floor

Today he extended the cables between units of an LED under-counter light system, and taped the lights temporarily in place to see how well they illuminate the interior.

This photo shows two of the three LED lights, one above the west window, and the second on the south wall. The third light is out of view on the north wall. Two switches by the door control two adjacent duplex recepeptacles, one for the interior lights, and another for a small exterior LED "porch light."

 

March 25, 2018 – Lights installed

Mike cut six blocks with a 20° angle to attach the three LED lights to the walls. He glued the twisted-pair extension cables to the walls with Goop, and declared this job complete. Here is one light and its mounting blocks.

 

March 31, 2018 – Roof opener installation

The roof opener is about 75% installed. Mike discovered it is easier to install it according to the directions – but upside-down, instead of on its side as originally planned. The spacing and alignment worked out much better than expected in this orientation.

 

April 5, 2018 – Roof opener works!

Mike finished installing the roof opener, then wired the pushbutton control and an obstruction sensor that isn't needed but must be connected for the opener to operate.

The motor (circled) is bolted to the north and east walls, and the opposite end of the track is bolted to the south wall. This view shows the track along the east wall with the trolley and its red release knob, plus the linkage to the second roof truss.

After final adjustments to position sensors, Mike tested the opener using a wireless remote. It works! It effortlessly rolled the roof open, then closed it at a slightly slower speed.

Videos

Here are two videos showing the roof in motion. They open in a new browser window, so close it to return here.

 

April 8, 2018 – Computer desk

Mike installed the computer desk he made several weeks ago. It's in the northeast corner, 44" above the floor for convenient stand-up use.

 

April 9, 2018 – Ethernet

Mike plugged the Ethernet cable running from the network closet in the house basement into a 5-port switch, and confirmed a good connection. It's been three years since he first checked out the Ethernet. Happy to see it still works.

Mike also installed an Ethernet power controller similar to this one under the desk on the north wall. It uses commands sent over Ethernet to switch AC power to eight receptacles, so we can turn on and off individual pieces of equipment from inside the house.

A second 8-port switch will be installed by the telescope pier to control power to devices located there.

 

April 12, 2018 – Equipment mounting platform

Over the past couple of days, Mike made a platform to mount certain equipment near the telescope. It clamps to the 12" lower section of the concrete pier, and has pairs of wooden beams that provide mounting points for brackets and shelves as needed.

As seen in this photo, the south side of the platform holds the second Ethernet power switch above a DC power supply for the telescope mount. The north side will hold smaller power supplies and the hand controller for the telescope.

A critter screen keeps out rodents, snakes, and other curious animals (but not bugs, which come in around the roll-off roof). The screen also catches small parts that drop while working on equipment at the pier. It is attached with construction adhesive to the pier and to the sides of the floor hole.

 

April 14, 2018 – Final steps

Mike pulled a "messenger string" through the 3" conduit from the computer desk to the pier. This string has a loop in the center to allow cables to be attached and pulled through the conduit in either direction.

At Louise's behest, Mike also modified a PVC reducer fitting to make a collar for the cable conduit. It looks nice, but required an inordinate amount of work for such a small benefit.

There's more wiring to do, including installing the computer and connecting it to the telescope and camera, but today Mike installed the telescope.


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Updated April 15, 2018