For detailed step by step instructions: http://www.instructables.com/id/Bluetooth-Controlled-Recycled-Rainbow-Lamp/
This Bluetooth Controlled Rainbow Lamp can be switched to any color by using your smartphone. The lamp not only looks like all the seven colors of the rainbow but also glows in all the seven colors of rainbow. The shapes that it makes at night are just amazing to watch. The design of this lamp may seem complicated, but you will be surprised to know that it is made by just cardboard, nothing else! Actually the original design was taken from crafts thrift . I made little modifications in the design. You can reuse your old cardboard boxes to bring them back to life by making it instead of throwing them away. Since it uses old cardboard which is reused to make it, that makes it recycled. You can use it as a night-lamp or for decorations in certain events. It can be hung on the ceiling with the help of the string or can be simply kept on a table.
The electronics of the lamp that makes it glow in different colors comprise of an arduino that acts as the brain of the lamp, bluetooth module that receives signals from the smartphone and RGB leds that gives out light of different colors. When you touch your phone to produce a certain color, the smartphone sends a command which is received by the bluetooth module. The module then transmits that data to arduino which processes it and makes the led glow in certain brightness. The brightness of each color of the led can be controlled as they are connected to the PWM pins of arduino. If all this seems complicated, just calm down and skip all this.For detailed step by step instructions: http://www.instructables.com/id/Bluetooth-Controlled-Recycled-Rainbow-Lamp/