Instructables
Everyone loves looking at the stars. Unfortunately, city lights, clouds and pollution often prevent this from being a frequent passtime. This instructable helps capture some of the beauty and most of the romance associated with the heavens and puts it on your living room or bedroom ceiling.

The premise is simple. Make holes in a bowl and shine a light behind it to make stars on the ceiling.

The completion is quite a bit more complex, due to some pesky laws of physics that I'll explain in the next few steps. The end result is a curious looking device that will definitely get lots of remarks, especially when you turn it on.

Unfortunately I didn't think of making an instructable for this until after I had completed the project. It was a gift for a special someone and I didn't want photographic evidence being accidently discovered on my computer or her camera. I'll try my best to be comprehensive and thorough with the pictures I've taken.

This instructable makes minor assumptions that you have basic soldering skills and knowledge of how to use hammers and typical hand tools.

Please vote for me in the Get The LED Out! Competition! Voting ends on June 21st!
 
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Step 1: Materials and Tools

Picture of Materials and Tools
The parts and tools I used for my build are listed below. Naturally you can swap anything out for an equivalent item you think will work just as well. I had a machine shop at my disposal so I made mine entirely of metal. Opaque plastic or wood would do just as well.

Materials:
-Metal bowl
-3W white LED
-Wood dowel, 1 inch diameter
-Steel sheet metal
-Pop rivets
-Rubber sheet
-Self-tapping screws
-Batteries and holders
-Switch
-1.5ohm resistor
-wire
-M3 screws and corresponding nuts
-Map of constellations
-Masking tape
-Non-gloss black paint
-Thermal Grease
-Metal washers
-Fibre washers

Tools:
-Center Punch
-Hammer
-Vice
-Drill
-Pop rivet gun
-Wrench
-Pliers
-Screwdriver
-Hot glue or otherwise
-Jigsaw
-Hacksaw
-Printer
-Scissors

Optional Tools for the well-equipped:
- MIG, TIG, Arc or Oxy Ace welding tools
- Bandsaw
- Metal cutting press
- Bending press
- Nibbler
- Press break

Step 2: All-Important Science

diagram2.png
IM000022.JPG
The interesting physical property of pinholes is that they function like a lens. This principle is in cameras, projectors, and most notably, our eyes.

In our case, the lensing effect doesn't make a visible change to our lights, since the source is round and the projection is round, through a round hole. The one important thing that must be kept in mind when choosing your light source is this; a wide light source makes a wide projection, and a small light source makes a small projection. We want tiny pinpoint stars, so we want the smallest brightest source possible. The diagrams in this step visualize it for us.

Putting a normal lightbulb inside the bowl will not have the desired effect, so a high powered LED must be used. Also, only 1 LED can be used, or else more than one projection per hole will appear.

Step 3: Making the Constellation Bowl

The first step is punching the holes in the bowl. Drilling was impractical because 1mm drill bits are too fragile to be drilling hundreds of holes in the steel bowl. I bought my bowl for $1 from Dollarama, a thin stainless steel mixing bowl.

Place the dowel in the vice, gripping it very firmly. This piece is going to be the resting piece, and will be destroyed in the process, so don't use expensive wood or something you want to keep.

Print and cut out your constellation chart. You may need to try a couple times printing at different sizes until you find one where your constellations will all fit reasonably well on your bowl. Tape them down with masking tape. Place the bowl on top of the dowel so that the inside of the bowl is resting on the dowel and the outside where your constellation paper is is facing towards the ceiling. Place your center punch on the star, and hit it with the hammer. Practice until you make a hole that is roughly 1mm of open diameter. The surrounding will be slightly dented, and the hole won't be round, but don't worry.

The reason that we hammer from the outside is because the opposite side of the metal will be extremely sharp, so having the sharpness on the inside is better and safer in the end.

After you complete your constellations, feel free to make as many random stars as you'd like. I made enough stars that theres lots to see and the constellations are well hidden, but not lost completely. This part is purely up to you, and you can add more later if you want to.

Step 4: The Skirt

Since the bowl and the base will probably not be light-tight, as was my problem, we need to seal it. We can't seal it permanently, so we need a way to block light that we can remove easily. What I did was punch large holes near the lip of the bowl and rivet a sheet of rubber around the inside. This slides down into the base and blocks the light from the LED that might have escaped through the crack.

You will need to punch four holes around the rim of your bowl that will let you screw it down onto your base. Punch these holes larger than star holes, as big as you need so that your screws can pass through without threading.

Also, the inside of the bowl needs to be painted with black paint. Reflections off the inside can reflect out the opposite side and create strange shapes on your ceiling and walls.

Step 5: Constructing A Base

The base is the next piece of the puzzle. Since the LED has a 120 degree spread, we can't put it level with the lip of the bowl, or we wont have light coming out the holes that are close to the horizon. We need to lower it down about 1.5 inches. I did this by fashioning a metal ring out of sheet metal and making a steel bottom that my LED bolts onto. You could just as easily make a plastic or wooden one if thats easier for you. All that matters is that it is NOT SEE-THROUGH. No light can escape out of anywhere other than our star holes.

Filling the bottom with rubber or painting the inside black is a good way to make sure there are no reflections inside the device. Filling any gaps in the sides or bottom is also crucial, as any escaping light will be visible on your ceiling and walls.

Cut, bend and drill four small brackets that will let you mount your bowl onto your base. Attach them to your base with rivets so that they line up with the four holes you made in your bowl edge.

Your LED needs to be bolted to the bottom of the base, so drill two holes that line up with the notches on the LED that you purchased. Put a tiny bit of thermal grease under the LED so that it conducts its heat into the metal base. If your base isn't made of metal you might want to put the LED on a metal plate in the bottom of your base.

Step 6: The Light Circuit

The circuit is very simple, and consists of three batteries, a resistor, a switch and an LED, all wired in series.

Construct the circuit as shown below. The LED I used was a 3W hex base LED running at 3V and around 1A. The value of R will change depending on what LED you use, and you should be able to calculate the required value using the LED calculator at http://linear1.org/.

Your switch can be mounted anywhere. I put a nice big toggle switch on the front.

Step 7: Stargazing Time!

Screw the bowl down onto the base, and you're done! Turn off the lights and give it a try. If you see strange non-round lights on your ceiling, that means something is reflecting light inside your planetarium. While its on, check the outside for unwanted light leaking out.

I tried to photograph the effect, but without a SLR or tripod capturing the effect well is nearly impossible. The photo does it no justice.

I gave mine to my girlfriend as a birthday gift, and she absolutely loved it. Lying in bed with the Planetarium at your feet is a lot of fun, pointing out the constellations and gazing in wonder. No doubt anyone who recieves one as a gift will be extremely impressed that you made it yourself.

Things to change/improve:

-The result would look better with an even brighter light and even smaller holes
- Having several light sources would allow for more stars with fewer holes, but the ability to have identifiable constellations is lost.
- Adding a wall power adapter would make for a very nice nightlight.

EDIT

Another great add-on would be to add a low-RPM motor on the inside and have the bowl rotate on the light very slowly, just like the actual night sky. I thought of this while building mine but the noise and mechanical issues made me drop the idea pretty quickly, but someone could definitely find a way to do this.

I hope you enjoyed reading my first instructable, thank you very much for reading.
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Thank you so much for the idea! I was trying to figure out a way to make a portable planetarium for my astronomy class and found your instructions. The kids have had a blast designing and building the parts. We are using a steel mixing bowl and house current for power. We have also mounted the bowl and base on an old telescope tripod. The theater is a black tarp in the shape of a dome that we inflate with a large fan. We are still working on all the parts and will post pictures of the end results as we get them done. The comments from others have been very helpful too. Science never sucks!

latifmak10 months ago
HHHmmmmm........................Can you link this?

search4electronics2013.blogspot.com
AmateurGus1 year ago
Hey Matt, awsome project, congratz.
I did my own based on your design, only a few changes, power source from the wall socket, small things like that.
I used a 3w Blue Led, it gives u more of a star effect i think, it's less "light" but more defined dots. Also, adding a LM317T is great to get constant controlled current is a good idea. Also, instead od rivets, just bolts and nuts, so you can open it an fix it just in case.
My little niece loved it, i really appreciate your idea Matt.. keep'em coming.
mattthegamer463 (author)  AmateurGus1 year ago
Glad you liked it and that it went well for you. Mine does open of course, it eats batteries pretty quickly. There are a few screws around the rim of the dome that allow it to open up. This was a really early project of mine, before I knew much about metalwork or electronics, but it still turned out really well. I built a 2nd one a year later using a power inverter to let me wall power it, but it didn't turn out nearly as nice as this one, unfortunately. The higher power LED I used had a square emitting surface inside it so all the stars turned out square as well! And the switch mode supply I put inside it makes whiny noises when its running.
didibemi1 year ago
Matt! That's an extremely great idea! I've already done one of those with a shoe box, and a flashlight (as the paper doesn't reflect light). It worked out of the box!
Then, I bought one of those http://www.prlog.org/11168760-star-sky-projector-lamp.jpg
Anyway, it was worse then I expected.
I like the way you did yours, and I'll do one this weekend. I'll buy the LED's tomorrow. Great Instructable! I'm planning to include a blue light inside the box also, so that if I want a "calming" and "relaxing" light, I could use it! :D

mattthegamer463 (author)  didibemi1 year ago
Glad to hear you like it, thanks.
if you added a Fresnel lens then the possibility of adding more light sources and maintaining ledgeble constellations easy, there relatively cheat usually made of plastic so you could cut it to fit nicely inside
Fresnel lenses bend light so that it flows straight off the lens
mattthegamer463 (author)  SmokyDaStona1 year ago
Yes you are right, definitely a possibility.
tinker2342 years ago
you could use a very quiet motor and some spray on noise insaulator for carrs to make it spin
a motor that spindles the plate in a microwave oven (you can get a new one for $5) is just fine for that
saiqhussain2 years ago
Its awsum . I'll lv to make it !!
Coffeebot3 years ago
Awesome 'ible, Matt!

I'm working on a similar project, and I'm trying to determine the best light source. I noticed through the comments, you said that your final photo was a long exposure, and the stars were about 2" diameter -- that implies these aren't super bright on the ceiling.

Is the end result bright enough to function as a decent night light? You did mention using it as a nightlight, but how does it compare to a traditional lightbulb-based nightlight?
mattthegamer463 (author)  Coffeebot3 years ago
Hey, glad you like it. :)

If you look at the science of Step 2, you will see how I explain big and small light sources, and the effect they have. Ideally you want as bright as possible, as small as possible, and the light-producing portion of the source (ie filament, LED internals, or a frosted bulb) to be round. A normal bulb with a straight line filament will little straight lines on the ceiling instead of stars.

The stars aren't particularly bright, but this is only a 3W LED. A higher power LED, or adding more holes makes more light.

As a nightlight, it might be good for a child, but won't do much to prevent you from stubbing your toe on your bed frame. All the light is aimed at the ceiling, not the floor, making navigation difficult. If your eyes are even partially adjusted then the reflected light off the ceiling would probably work well enough to find your way to bed.

Feel free to ask any more questions. Hope I helped you out.
Thanks for the quick response, Matt!

I picked up a 1W cluster of 6 high intensity LEDs at the local Fry's; not without a great deal of skepticism, either.

Oddly enough, using a colander, it lit up the living room pretty well. My wife didn't think it was enough light to function as a nightlight for a fearful child, but it did the job I wanted. Plus, the colander is metal, and has huge holes in it, so a smaller dome, with a black interior and smaller holes will likely do a better job.

Functioning as a nightlight, I'm going to add additional lights elsewhere, but probably only with standard 5mm LEDs.

Thanks again, and once I have something worth showing off, I'll post some pics!
mattthegamer463 (author)  Coffeebot3 years ago
Sounds good. Keep in mind that smaller holes reduce the amount of light in a non-linear fashion; a hole with a 50% smaller diameter only lets out 25% as much light. Also, the number of stars you see is number of holes x number of light sources, so with 6 LEDs you should see a lot of stars. This is great for making less work, but if you want actual constellations you will lose them all. You'll have six big dippers, etc.

Hope it all works out.
Yeah, I'm not intending to make it a realistic representation. My girl is 2...astronomy lessons don't start until she's 3. ;)

Thanks for the tips on hole size, too. I'll keep an eye on that. Some experimenting will be necessary!
mattthegamer463 (author)  Coffeebot3 years ago
Tin foil is a perfect way to experiment without wasting metal bowls or anything.
its not bad
teran_934 years ago
yeah it is good
escalar4 years ago
VERY NICE!
AWESOME GADGET
SeaBreazy5 years ago
Putting it on top of a clock motor should do the trick. Try to find one that rotates continuously rather than one that ticks.
I would think this assembly is far too heavy for a clock movement.  They simply do not have the torque, as they are designed to spin relatively lightweight "hands".  There are "high torque" clock movements, but they can only move a couple of ounces at best, and I would guess this is way more than that.
Oh, I forgot to mention that a Google search for "2RPM motor" will give you a ton of options, many of which are AC (no power regulation or adaptation issues to deal with) and very strong (spin 25 POUNDS!), so no doubt one of them would work nicely. 
mattthegamer463 (author)  Whackmaster4 years ago
2RPM would be a little quick though, I would think someone would get dizzy.

A PIC and a stepper motor would probably be a more realistic solution, for both a realistic or unrealistic rotation time.
You are very likely right!  I'm actually building a "starfield projector" using a 2RPM AC motor I pulled from a dead sewing machine, and indeed I am using a single gear to lower the speed to something more like 1/4 RPM.  I may even throw in a (very heavy) pot to drop the speed a little more (and before anyone harshes me I know that is not exactly efficient and at very low settings can stall the motor, but it works)

I use PICs myself, but sometimes a good old analog or mechanical approach is much more practical than programming a microcontroller.
mattthegamer463 (author)  Whackmaster4 years ago

deadinsect4 years ago
hey matt.

great project.

I was wondering, how big are the stars and far from the ceiling can the bowl be before you can't really see them?

is each star something like a 2" dot at 3 yds from the bowl? thanks, Anthony
mattthegamer463 (author)  deadinsect4 years ago
You would be about right with that assumption.  Unfortunately, if you decrease the hole diameters much more they won't let enough light through. 

With the bowl on the floor they're still quite visible.  I don't have a ceiling high enough to test any more than that.
usbfuse5 years ago
i made a telsa helmet with that
austin5 years ago
how bright was the led you used?
mattthegamer463 (author)  austin5 years ago
The LED is a 3W LED, 3.6V @ 750mA The brightness is maybe similar to a Maglite. It hurts to look at directly.
catface995 years ago
i like.
johnpombrio5 years ago
Dang! Y'know I had just been thinking the same damn idea! Since the LED makes a good pinpoint light source and the holes are small enough, I figured it would make a great planetarium. And POOF I saw yours! LOL. I came up with essentially the same build concept, including hole punching (as I have built several punched copper lanterns). Agreed that trying to get a hole smaller than 1-1 1/2 mm would be really tough and a good tin punch is worth it. I would punch from the inside as I know from my lanterns that the edges of the holes are not that bad and that is the way tin punching has been done for hundreds of years. Would also make for a cleaner pinhole for the lightsource. The only difference would be to use my constant source current LED from Hong Kong. Lights two 3W LEDS from 120 volt. The other is to perhaps make the base a little deeper to "sharpen up" the stars. I would also use random holes as I already know my constellations pretty well! Did you try a deeper base? I wonder if it actually has to be hemispherical.. Does the bowl have to be black if the BOTTOM does not reflect? Meantime, down to my shop, set up an LED and start playing with aluminum foil for some basic research! Thanks for the great idea that you mindmelded from me!
mattthegamer463 (author)  johnpombrio5 years ago
To answer your questions: If your base is too deep, you limit the angle of stars you will have. If its too deep, you start cutting off your horizon stars. The bowl has to be black on the inside, because light reflecting off one side of the bowl goes out the other side. To be honest, punching from the inside just isn't practical. The material bent outwards by the punching process is extremely sharp, and your bowl is now a giant cheese grater ready to slice up your hands. I don't think they have any noticeable effect on the holes. Thanks for checking out my Instructable, be sure to vote for me in the LED contest!
O.K...please don't laugh. I know nothing at all about electronics, but ..I'm just wondering if a "dummies" version could be made by putting a flash light underneath a food strainer (with the light pointing towards the holes) Ummm is this a really stupid idea? (Please be kind)
mattthegamer463 (author)  porcupinemamma5 years ago
If you found a food strainer that had small holes (around 1mm diameter) then it would work decently. The strainer has to be light-proof, so if it was plastic you would probably need to paint it with black paint until no more light can get through the plastic. The problem with a strainer is that the holes are just boring patterns, but you could glue pieces of tin foil behind most of them to block them, and make star patterns. Give it a try.
Wow! Thanks for your help, very kind of you. I plan to try this with my grandaughter. Obviously yours is WAY cooler, but I appreciate that you've helped me make a simplifies version. :0)
mattthegamer463 (author)  porcupinemamma5 years ago
I thought of a better way you could try. Take one of the mesh stieve strainers, cover it with aluminum foil, and poke holes in it with a pencil. That will give you the freedom to put holes in star patterns, and still be cheap and easy. Also, you're quite welcome. :)
You're brill bro! thanks :0)
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