This is my very first ever Instructables upload so please, be gentle with me.
I made this for a small gallery space at an ARI called Constance in Hobart, Tasmania, Australia, and was specifically designed to be activated when people look into a mirror and see their own reflection. The conceptual premise was to inspire the audience to think about reality and how it is made by us, hence a self activated private universe, but you could play with the variables of this hack to do so as you please.

Step 1: MATERIALS

You will need:

-Star Master Projector Lamp (Kmart)

-Outdoor Motion Sensor Light. Look for a small model with 2 seperate LED's on either side of the sensor (Hardware Store)

*Please note that these two devices need to have the same voltage reguirements or you will have to get tricky and put extra bits to keep the circuit equivalent to the power voltage so as to include the RGBs from the Projector Lamp into the existing motion sensor / LEDcircuit.

-Dremel Hand Drill or some kind of Hand Saw
-Staple Gun and Staples
-Precision Screwdrivers

-Jewellers Pliers

-Electrical Tape (white and black Nitto)
-Double Sided Tape
-Black Gaffa

-Sharpie

-4mm Black Cable

-Soldering Iron and Solder

-Ply Wood for backing the foam core

-Foam Core 2x 1x 1m taped together

-Fibre Optic reels plus plus fibre optics housing for a 2x 2m .5mm and 1x 1mx 1mm reels. (EBAY)
(You will need to consider how large you want to make your universe, mine was reasonably small so I used the smallest width I could find on ebay but if you are making a massive ceiling you will want to get a lot bigger and multiple variations of size to really look like a universe.)

Some optionals?
I also needed a picture hanging kit and black fabric and black paint for building a room to house my universe as it was displayed as a false ceiling inside the gallery space. How you implement this hack is entirely up to you! For now I will keep the Instructable focused upon the electronics.

Step 2: BASIC SCHEMATIC

Basically you are going to hack a motion sensor LED light to become a fibre optics kit that includes an RGB colour change star projector into the circuit.

It is simply a case of clearly identifying the positive and negatives on each circuit board and keeping track of them because by the end you will have resoldered every connection using much longer strands of black cable so as not to be seen in the dark, and to allow you to have each object in the circuit several metres apart from each other.

You will need a big wide open space to lay everything out on without getting tangled up.

Step 3: BREAK YOUR SENSOR LIGHT AND EXPOSE THE CIRCUITS/ PCB's

Pull apart the outdoor LED motion sensor light bought from your local hardware or cheap crap store, being careful not to damage any of the parts, especially the motion sensor. I just shoved a screwdriver where there were signs of pcb and crowbarred the sucker out, breaking most of the casing, as I only needed part of it.

Take out all of the circuit boards and have them exposed and ready to be soldered. There are two LED Lights and the motion sensor that each have their own pcb.

When you have clearly marked all of the positive and negative joins, cut out LED 2 from the circuit entirely.

Because I am easily confused I left a few centimetres of cable attached to the MOTION SENSOR PCB clearly marked in sharpie ink LED 2 + and LED 2 - so I knew where to rejoin the circuit. But it is pretty easy as all the LED's and power are soldered to the corresponding + and - in the same spot on the motion sensor pcb.

SUBSTEPS...
After doing this I cut the plastic housing down to make a smaller house for just the motion sensor and switch.

Once you have done this clearly identify and label all positive and negative cable connections on both the LED's and the MOTION SENSOR PCB and only then, cut all the cables. You can draw straight onto the circuit board, I marked my cables and cut and soldered each positive and negative as a group so as to avoid confusion and tangling and because they actually needed to be soldered all at once onto the same spot on the MOTION SENSOR PCB.

I was lucky that this is a very basic circuit so all the positives and negative cables were easily identified.

Step 4: BUILD YOUR OWN FIBRE OPTICS CASE

You will now need to build your own Fibre Optics LED case. I had an existing case from a broken driver but you could use anything reasonably lightproof really, an old shoebox, old paint tin, you just need to think about cutting a reasonably accurate circle to house the Fibre Optics reel, but so long as you have Black Gaffa on hand, everything and anything is possible.

So anyway I double sided and electrical taped the LED to a piece of plastic that I slotted into the back of the driver ( SEE IMAGE 1)

After you have locate the positive and negative wires both on the motion sensor pcband the LED pcb and clearly labelled them, cut four long strands of black cable to resolder the joins with the desired amount of slack, you can taylor to your own needs but in this case I cut 2.5 metres in order to reach up into a false ceiling.

Now I resolder the 2.5m strands of 4mm cable from the motion sensor pcb to the LED pcb, being careful to thread any cable in through the back of the driver before resoldering to the LED circuit.

Step 5: POWER UP!

Clearly label and then disconnect the positive and negative cables connected to the battery housing/ power source in the motion sensor circuit and re-solder the desired length of clearly marked + and – to a new case.

It is really up to you what you use, you could keep the original casing in tact and use that if you don't want to hide the power source add or don’t add more cable length. I wanted to tuck it behind a plinth so I added a couple of feet extension and chose a small discreet housing from the bottom of an old RGB colour changing lamp, but you could build your own or use any kind of battery holding bit of business as long as it has the desired amount of voltage, which, in this instance was 3x 1.5 Volt AAA Batteries.

Step 6: HACK THE STAR MASTER PROJECTOR

Open up the star master being VERY VERY gentle and trying not to hurt the buttons or damage the circuit board.

Locate the positive and negative power source on the RGB Star master circuit and label them.
Then re-solder in several meters of cable to the positive and the negative on the star master circuit, and back to the positive and negative where you cut out the second and unnecessary LED’s from the motion sensor circuit.

WHEN ALL JOINS ARE COMPLETE, TEST THE CIRCUIT!!!

At this point it would be great to know it is working, before you start threading all those optic cables!

Step 7: BUILD a FALSE CEILING

Take the foam core and lay out next to each other.
Gaffa tape the two pieces together as evenly as possible.
Take both lenghs of ply wood, I used some that were about 40x 10mm and long cut them to run most of the length of the foam core (about 1.5m each).
At both ends of each length of ply wood attach a picture hanging hook.
Place the wood on the ground. Take the foam core, and line it up over the top of the wood so there are no overhangs.

When you are happy staple gun the bajeezus out of it, ensuring that the foamcore attaches to the wood supports properly. I had some giant dog clips on stand by just in case but I did not need them.
If you had time you could also use glue to reinforce the join but I was in a hurry.

Step 8: SOW THE STARS!

Now, take a precision tool that is roughly the same width as your optic cables, (so .5 or 1mm) and stab random holes into the foamcore so in the rough pattern of stars in the sky. (This is where you will have to get your creative on).

Now you can start threading the fibre optics through the holes you just stabbed with the precision screwdriver.

Here are a few hot tips on technique when threading:

Lay out the optics, putting the optics house where is will live once installed. This way you can find the least resistance for the optic fibres to start fanning them out evenly across the foam core.
If you have different sized and width fibres, be careful to distribute evenly across the foam core.
If you can, grap the black nitto and tape down a floret of fibres in intervals and then fan out from that cluster.
When you are feeding the fibres through the holes be careful to pull them all the way through or you won't see them.
If you break or damage or bend the fibres, you can just cut them below the point of damage and it's good as new!

Step 9: INSTALL IT.

So this part is entirely up to you.

This is what I did:

Screw four hooks into the ceiling from which to suspend the foam core. Thread picture hanging wire through each hook and hang and tie of each corner consecutively.

I also hung a curtain to limit the space to roughly the size of my false ceiling.
The space I used was painted black but for optimum star projection colours it is best on white walls.

I hung the sensor above a mirror in the space so when people approach the mirror to look at their own reflection, they activate the night sky above and also the star projector that is positioned just below the wall mirror, or the viewers face on a plinth.

It is in a very dark room so it is pretty hard to show you what it is like in photograph. I did not have the option of taking a long exposure to show you what it looks like so I drew a diagram so you can get the idea of the set up.

So there you have it.
A DIY Motion Sensored, Self Activated Private Universe.