How to build an LED Planetarium

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!

Step 1: 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

Comments

[AmateurGus]

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]

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.

[didibemi]

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]

Glad to hear you like it, thanks.

[SmokyDaStona]

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

[SmokyDaStona]

Fresnel lenses bend light so that it flows straight off the lens

[mattthegamer463]

Yes you are right, definitely a possibility.

[tinker234]

you could use a very quiet motor and some spray on noise insaulator for carrs to make it spin

[mguima]

a motor that spindles the plate in a microwave oven (you can get a new one for $5) is just fine for that

[saiqhussain]

Its awsum . I'll lv to make it !!

[Coffeebot]

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]

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.

[Coffeebot]

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]

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.

[Coffeebot]

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]

Tin foil is a perfect way to experiment without wasting metal bowls or anything.

[awais mughal]

its not bad

[teran_93]

yeah it is good

[escalar]

VERY NICE!
AWESOME GADGET

[SeaBreazy]

Putting it on top of a clock motor should do the trick. Try to find one that rotates continuously rather than one that ticks.

[Whackmaster]

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.

[mattthegamer463]

[Whackmaster]

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]

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.

[Whackmaster]

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.

[deadinsect]

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]

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.

[usbfuse]

i made a telsa helmet with that

[austin]

how bright was the led you used?

[mattthegamer463]

The LED is a 3W LED, 3.6V @ 750mA The brightness is maybe similar to a Maglite. It hurts to look at directly.

[catface99]

i like.

[johnpombrio]

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]

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!

[porcupinemamma]

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]

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.

[porcupinemamma]

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]

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. :)

[porcupinemamma]

You're brill bro! thanks :0)

[A.C.E.]

you could probably unscrew the top of the flashlight, if you have one of the big ones with all the reflective stuff in the top, so just the light bulb is there to get a better effect and wider light angle

[porcupinemamma]

Thank you for your help; another great idea-spectacular :0)!