This instructable shows you how to make a solar powered rainbow disco ball! A tiny solar panel powers a motor that turns a few cut glass crystals in the sun. These project moving rainbows around your room!

We use what is called a solar engine to make this work. A solar engine is like a bucket that slowly collects the photons from the sun until the bucket is full. Then we empty the bucket all at once into the motor which turns a tiny bit. Even then, the motor isn't powered enough to move the crystals much, so we also need a gearbox.

If you want to know more about how solar engines work, read up on the BEAM website.

This instructable makes use of a PCB to make the construction easier, sturdier and better looking.
You can buy a PCB from me at cost price (£1.50)

You can also use a veroboard, or you can solder it all together with no board. In which case, have a look at the attached circuit diagram.

You'll need some basic soldering skills to complete this project, so if you're unsure then check this instructable.

Step 1: Components and Tools

Components:

* solar panel (this turns the photons from the sun into electrons),

* C1: 2000uF or greater capacitor (this is the bucket that collects the electrons),
* motor and gearbox (this is what we power with our bucket of electrons),

* T2: 2n3906 PNP transistor (this is part of the switch that empties the bucket),

* T1: 2n3904 NPN transistor (this is another part of the switch),

* R1: 2k resistor (this is another part of the switch),

* D1 and D2: 1n4001 diodes (this is the bit that detects when the bucket is full enough),
* veroboard, a PCB, or just solder it all together in situ.

* cut lead glass crystal(s) at least 20mm wide for big rainbows!

* window sucker,
* thin cable tie to attach the motor,
* connector block to attach the crystals to the gearbox shaft.
* some thread, or fishing line to attach the crystal(s).

Tools:

* glue,
* soldering iron, solder,
* wire cutters,
* small flat head screwdriver,
* maybe a sharp knife,
* maybe a file.

The total cost of components comes to £9.51 if buying in quantity. If you want a complete kit, please email me.

Step 2: Build the Solar Engine Circuit

Now have a look at the board. You can see there are markings for different components to be soldered in. Sometimes you'll need to bend the legs of the components to fit in the holes, and sometimes you'll need to make sure the component goes in the right way round! Let's start with C1:

C1: We have to solder the capacitor the right way round. It will have a stripe with - signs on it. This is the negative side. The board is marked with a +, so make sure the + of the capacitor connects to the + on the board. Check the photo for help.

D1 and D2: Diodes matter which way round they go too! The stripe on the board corresponds to the stripe on the diode.

T1 and T2: Make sure you use the 2n3904 for T1 and the 2n3906 for T2. Put them in so that the outline on the board matches the shape of the component.

R1: 2k resistor, this doesn't matter which way round it goes.

We'll solder on the solar panel and the motor later.

Step 3: Attach the Sucker

You may need to file out the hole slightly to fit your sucker. Make sure it's a tight fit though, so it doesn't fall!

I've found screwing it into the hole can help it fit in more easily.

Step 4: Solder the Motor and Panel

Solder the motor to the PCB. It doesn't matter which way round the motor goes, just connect the leads to the connections marked motor+ and motor-.

Your solar panel may not come with leads, in which case solder a thin black wire to the negative side and a thin red wire to the positive side.

Solder the solar panel to the connections on the PCB. Make sure the red goes to solar+ and the black to solar-

Step 5: Test the Circuit

Now is a good time to test that everything is working properly. You'll need bright sunlight for there to be enough energy to turn the motor.

See this video for help: http://youtu.be/YR4wnIjNZGE

Step 6: Assemble the Gearbox

Check the cogs first. Sometimes they have little bits of plastic in between the teeth, which will stop the gears turning properly. If so cut them out carefully with a knife. The small cog goes on the motor and the others are used in the gearbox. One of these is a spare so don't worry about having a cog left over.

Push the smallest cog onto the motor shaft so that the teeth are on the top. Then carefully fit the motor inside the bottom black casing.

Put one of the big cogs onto the little black peg next to the motor with the big cog at the bottom and the little one on top. Check that the small motor cog meshes with the new cog.

Then put another of the cogs onto the other black peg and check that this meshes with the previous cog.

Push one of the cogs onto the metal shaft about half way down.

Fit the metal shaft in the gearbox so that the big cog is on the bottom and the small cog is on top. Check that everything still turns smoothly.

Finally, fit the top of the gearbox on and push it together round the edges. This can be quite stiff, but look to see where each of the 3 pegs locate and give some good pressure there.

Make sure that you can easily turn the long metal shaft and the gears all move smoothly inside. If you can't move it easily, the motor won't be able to turn it either.

Then push the motor into hole in the gearbox and test it again. You should see the shaft moving like in the video:

http://youtu.be/YR4wnIjNZGE

Step 7: Attach the Motor

Use a cable tie to fix the motor gearbox to the PCB. There are 2 small holes at the bottom of the PCB to thread the cable tie through.

Start off by threading the cable tie through the holes, from the front of the board to the back, then through the next hole and out to the front again.

Put the motor gearbox's flat side down on the board and fasten the cable tie around it securely.

Step 8: Attach the Solar Panel

Glue the panel to the PCB at a 45 degree angle - facing the back of the board. The angle is important as it needs a good view of the sun when it's in a window.

Step 9: Attach the Crystals

Tie a 10cm loop of thin thread or fishing line round the crystal and then thread this through the connector block. Put the crystal through this loop and pull tight.

Then put the connector block on the gearbox shaft and tighten up.

There isn't a right or wrong way to do this, as long as the crystals are firmly attached to the shaft of the gearbox.

Step 10: Finished! Stick It Up on a Sunny Window!

If things don't work, here are some things to check:

* Check this video for help with the motor and gearbox: http://youtu.be/YR4wnIjNZGE
* The solar panel or capacitor is soldered the wrong way round. The negative side of the capacitor has to attach to the gnd connection, as does the black lead on the solar panel.
* You used a zener or flashing LED instead of D1 and didn't solder a wire over D2.
* Something isn't soldered right - check all the joints again.

Step 11: Attribution

This project was inspired by a ready made solar rainbow maker that I bought as a Christmas present for my sister Rosie.

I decided to make a DIY version, and in doing so learnt about solar engines. I learnt all about solar engines from the fantastic BEAM site.

This is the first PCB I've designed, and I used the free demo of Eagle.