Greetings! I’m happy to make my introduction here on the Re:Farm blog. My name is Andrew O’Malley and I’m a Canadian artist/engineer. My main artistic interests are animated lighting installations and fixtures, and electronic music production and DJ’ing.
[ Eyebeam bio ]
These interests have brought me to NYC for the summer of 2010, where I’ve connected with Hernani’s Re:Farm project through his residency at Eyebeam.
My first objective is to create the PCB (circuit board) for the Re:Farm On The Wall module, a data visualization module using an LED display to present data away from the computer screen.
Here’s Hernani’s original sketch for displaying the soil moisture level from 6 sensors:
This design uses 7 LEDs to display the soil moisture level for each of 6 sensors (42 in all). The design concept has been formalized as seen below:
The module still has 7 LEDs for each sensor (or farm/garden), but with the addition of LEDs between the groups (for a total of 48) to create a complete circle which can be used with other templates, such as the one below, for visualizing other data such as temperature or humidity:
Ideally, the board will also incorporate a stepper motor to drive a needle (like a speedometer) for an additional data channel.
I’m going to first concentrate on the LED display. Since the board will make use of an ATMEGA microcontroller (Arduino) chip and an XBee radio (to receive the data), real estate on the approx. 3″ x 3″ board is already a bit tight, so I am currently researching Charlieplexing, an LED driving scheme which allows N*(N-1) LEDs to be directly driven by N pins of the microcontroller. 8 data pins from the microcontroller can thus be used to control the 48 LEDs since Charlieplexing with 8 pins allows control of up to 8*7=56 LEDs.
At The Next HOPE conference this past weekend, Jimmie P. Rogers was demo’ing and selling his LoL (Lots of LEDs) Shields for the Arduino. He has a great post about his work with Charlieplexing which I’m currently consulting. Talk about serendipity!
In a way, the overlap between the needs of Hernani’s project and my own interests in lighting and internet-enabled lighting fixtures is serendipitous as well.