For the LED contest, I wanted to put lights on something that moves. Poi are something I've been tempted to try for a while, and seemed like a good application for LEDs.
Step 1: Materials
These poi are constructed from a pair of hollow rubber balls on ropes. I've inserted 5 LEDs in each ball, powered by 12V batteries. The ball is covered with a balloon.
Things you'll need:
- 2 hollow balls - mine are around 3 inches in diameter
- 10 (or more) LEDs and some spares
- electrical wire
- 2 12V batteries (it's possible you'll need more power if you use more LEDs)
- 2 balloons - I used 12 inch balloons
- electrical tape
- four large washers (to add some weight to the balls)
- velcro and conductive thread (I used these to make a switch)
You'll also need a soldering iron, wire strippers, a drill, a utility knife, a needle, and pointed scissors.
Step 2: Test your circuit
First, decide how many LEDs you are going to use. It is helpful to use a breadboard or similar to test the LEDs with your intended power source.
I ended up deciding to wire the LEDs in series and not use a resistor, but your circuit may be different if you use more or fewer LEDs than I did.
My poi use standard 5mm green LEDs. (I was originally intending to use super bright LEDs, but I broke one and didn't have a spare.)
The 12V batteries are conveniently small enough to fit inside the balls, and 1 battery provides enough power for the 5 LEDs.