Rainbow Stick and a Crystal Ball

Okay... There are plenty of Instructables here that explain how to build LED circuits, so we will not be reviewing that except to provide a few links.

My 'ible on Light Pens covers it as well as this tutorial on my web site.

Also see LEDs-for-Beginners. And search for LED to find many others.

Here are 2 recent creations.

The first is a light stick I built for the Maker Faire. It is a great light drawing device that will make a big picture quickly. See our Best of Maker Faire Light Doodles here.

The second uses a geode we found in a rock shop which makes an unusual home display.

This device is an extension of our light drawing pens. I strapped 6 different colored LEDs to a 2 foot long stick with 3 AAA batteries and a switch postioned to easily turn off and on with your thumb.

The 3 AAA batteries are wired in series for a total of 4.5 volts.

The LEDs are wired in parallel to the power source and the switch is inline so they all light at once.

Since each LED has a different forward voltage and maximum current load, I wired a different size current limiting resistor to each. Here are the specs.

Power source is 4.5 volts

LED...................| Forward Voltage | Forward Current | Resistance

Super Blue.......| 4.0 volts................| 25ma..................| 20 ohms
Deep Red.........| 2.5 volts................| 25ma..................| 80 ohms
Yellow Green...| 2.5 volts................| 25ma..................| 80 ohms
Super Orange..| 2.5 volts................| 25ma..................| 80 ohms
Light Green......| 4.0 volts................| 30ma..................| 18 ohms

We found an interesting geode in a rock shop. Typically geodes are hollow rock spheres that are opaque on the outside and quartz crystal on the inside. This geode had lost it's outer shell and remained intact except for a small hole about the size of an LED. I stuck one of my light pens in there and the sucker lit up like the Moon Rising in A.I.

So, I put 3 batteries together, wired 1 red and 1 blue LED in parallel (hoping to get purple), stuck them in the geode and set the whole thing in a bamboo cup made to hold an artist's paint brushes. For the time being, I twist the wires together to activate/deactivate the light, but a small switch drilled through the side or bottom of the cup will complete the lamp.

I think it looks quite nice.