For my next trick, I will attempt to add lights and an Arduino microcontroller to the coffee table. *drum roll, please!*
So how did I do this? Let’s start with a (very) quick background on programmable microcontrollers. These little guys have been around for a long time in various forms. Reduced to its basic concept, they are an embedded microcontroller development platform on which a user can write some easy-to-understand programming code that takes some electrical input (sensors, potentiometers, etc), processes the data by the code specified, and provides some output (usually in the form of lights, relays, motors, etc). That is an over-simplification of the capabilities, but once you understand how to program the microcontroller to complete these basic steps the possibilities become endless!! I have included a few links at the bottom of this post for further reference. For this project, I am using an Arduino Yun.
First, I had to add the lights. For this project, I chose to use 2 meters of WS2812 R-G-B LED strip lights from Adafruit (Link), in part because Adafruit provides a free Arduino-compatible header file… more on this later. I cut the LED strips into 4 segments, added a few soldered-wire leads to connect the segments, and affixed them to the underside of the table with double-sided adhesive tape.
Powering the LED’s can be a challenge. There are 120 tri-color LED’s in this project. Each LED can draw up to 60 mA of power (20 mA per color component) at full brightness. At a peak current draw of 7.2 amps (36 Watts at 5 volts), that is a lot of juice! A more reasonable average current would be 20 mA per LED (one color at any moment in time), resulting in a current draw of 2.4 amps (12 Watts at 5 volts). Either way, this power draw exceeds the Arduino specifications for it’s 5-volt V-out pin. Consequently, I chose to power the LED’s with a wall wart (finding one at Radio Shack that offers a 5V DC + 5V USB port with support for up to 5 Amps, so I can power both the LED light strip and the Arduino off the same power outlet). Following the instructions on Adafruits website, it is also recommended to add a large capacitor across the power supply and a resistor in-line with data signal so as to protect the LED string from harmful spikes in voltage. **For a more detailed explanation, see Adafruit’s website (link below.)**
I will write another post detailing some of the programming options and possibilities! Stay tuned.