RGB's are beautiful and fun to play with. However, to drive them requires some type of modulation circuit or micro-controller such as Arduino. I have been racking my brain for months to find a simpler solution because I have an Innovation Education Center for kids and I wanted something that the Mini Makers (under 7) could build and experiment with....finally...one of my daughters experiments provided the inspiration for a solution.

She made the first two prototypes. They worked, but we kept refining the design. And after 5 prototypes, we have created the world's simplest RGB LED driver. It's range is not as good as PWM...but what it lacks in range, it makes up for in simplicity! It can produce a decent range of beautiful colors. And its fun to experiment with on different fruit and moisture levels. Give it a try.

Materials:

A Citrus Fruit Peel (the thicker and larger the peel the better)
RGB LED (common cathode)
9 volt Battery
1k Resistor
6 Alligator Jumpers
1 Metal Chopstick (or a conductive rod of some kind)

Step 1: The Fruit Peel Preperaration

This is the most important part of the experiment, the fruit peel preparation.

1 Carefully take the peel off the fruit. Keep as much as you can in one piece and shaped with 3 legs.

2. Let it dry out for a few hours.

3. Soak it in water for a half a day.

Start this process first and then go work on the circuit.

Step 2: RGB Circuit

It's beautifully simple!

Put a 1k ohm resister on the common cathode of the RGB and jump it to the negative 9V battery terminal.
Attach the R,G,B LED anodes to jumpers and then to different corners of the fruit peel. Experiment with different locations and distances.
Then attach a jumper to the metal chopstick (or any conductive rod) and the other end of the jumper to the positive side of the 9V battery. Note: you can use more than one positive electrode. For example is you wanted a strong purple (one on red and one blue)

It should look something like this...