Liam’s planetarium

Before Liam was born, I decided it would be cool to make him a personal planetarium nightlight. I scoured the Internet and found something on Instructables that I modified since I don’t have a machine shop or 5 million tools. The result is a nifty device that works pretty well! ‘

Here is the finished product:

Liam’s planetarium completed!

How did I make it, you ask? No, I did not kill R2D2 with a shotgun and mount his head on a box.

The light source

The heart of the project is a simple LED circuit and switch. Knowing nothing about circuits I had to do a bunch of research to get myself back up to middle school physics level.

Science, son.

I got a 20 milliAmp, 5mm LED requiring 3.6 volts, and with a viewing angle of 100 degrees. If you just connect the LED to the batteries it will burn out, so you need to add a resistor into the mix.

Long story short, I got a four-AA battery holder which is 6 volts. Ohm’s Law says that V=IR, where V is voltage, I is current (Amperes) and R is resistance (ohms) , so with a 20mA LED requiring 3.6V, and a 6 volt power source, we need to solve for R, so R=V/I.

In this case we need to adjust V so that it is the source voltage minus the drop in voltage across the LED, ie 6-3.6=2.4 divided by .02 amps and you get 120 ohms of resistance. I used a 150 ohm resistor which is apparently within the margin of error, so it works!

I wired the LED to the resistor on a little circuit board, wired the resistor to the positive side of the batteries, and added a toggle switch which was then wired back into the LED. Soldering is probably best but I just twisted the wires together. Flip the switch and bam!

The box part

The corner braces give the box a cool rugged look.

The next step was to construct the base of the planetarium. I got four pieces of craft wood from Hobby Lobby and used glue and some corner connectors to put them together.

The sides of the box

The process was not what you would call very precise, but it worked. The L connectors were meant to go on the inside of a corner, but I liked the industrial look they gave it. Then I added a plywood bottom that fit inside the outer panels (glued and nailed) and sanded everything down.

Yuki was very helpful throughout the process

For the top of the box, I needed to cut a hole that the star dome would go on. The dome is a stainless steel mixing bowl, so I traced the bottom of the bowl on a piece of plywood, then cut the hole with a jigsaw about a half-inch smaller than the traced circle. That way there was an edge that the bowl could be screwed onto.

I decorated the box with space-themed stickers and put three coats of varnish on it (over the stickers). I also drilled a hole in one side for the switch.

My wish for Liam.

I put my Chinese chop on the bottom with a little inscription “sic itur ad astra,” – “Thus shall you go to the stars.”

The star dome

The dome is a simple mixing bowl with a lip around the top of it. To make the star holes, I used a star chart that had the arrangement of the stars and planets on June 6, 2012, which was Pumpkin’s due date. Turns out it is not his birthday, but still.

Star dome, before holes

I drew the constellations with a sharpie and then used a scratch awl to punch holes in the bowl. To make sure the bowl didn’t implode every time I made a star, I got a large dowel and clamped it vertically to a sawhorse. I lined up each star so when I hammered the awl into the bowl the tip would go through the metal and into the dowel, thus preventing the bowl from getting totally dented.

I spray painted the inside of the bowl black to avoid reflections inside the dome. I would recommend doing this after making the holes, because the hammer strikes kind of rattle the paint off. But make sure the paint doesn’t fly out of the holes and get all over the outside of the dome! Just nestle it in a drop cloth and problem solved.

Finally I awled four holes in the lip so I could screw the dome to the top of the box.

Hardware


Brass hardware is classy

Switch is in place…

Next I put the switch in the box, attached the lid with some nice brass hinges and put a little latch on the top so it can shut tight.

After the dome was screwed down, there was a small gap between the bowl and the top of the box. I took a piece of the rubber seal that attaches to the bottom of a garage door and cut it so it would fit inside the hole in the top of the box.

Latch! Not exactly child proof

Garage door bottom seal worked great to prevent light leaking out.

It stuck up too much so I trimmed it down so it wouldn’t block any stars. It actually fit perfectly inside the hole and had a little lip so it stuck in there good. I glued it down to fix it in place.

Final touches

I glued a small block of wood in the center of the box and attached the circuit board to it with velcro. I also velcroed the battery holder to the bottom of the box to keep everything in place.

Velcro keeps everything in place

Two wooden pieces glued to the side of the wood block made the compartments, and she was done!

Here is a view of the inside of the box:

The inside of the box, with compartments

Here is a list of the items I used to make this project

  • Six pieces of craft wood from Hobby Lobby/Michael’s
  • Plywood (4 foot square)
  • Metal mixing bowl with a lip
  • garage door bottom rubber strip seal
  • Corner brackets
  • Brass hinges
  • Brass latch
  • Small block of wood
  • Circuit: Battery holder, batteries, circuit board, 20mA@3.6V 5mm LED, 150 ohm resistor, wire, toggle switch (all from Radio Shack)
  • Velcro strips
  • Various screws and nails
  • Stickers
  • Varnish
  • Black spray paint
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