Just got a bluetooth enabled drawing robot working. It's based on Sandy Noble's [http://code.google.com/p/polargraph/wiki/Introduction Polargraph] and code+circuits from [http://www.mattvenn.net Matt Venn]. It uses a pair of stepper motors to wind a pen carrying gondola across a sheet of paper.
At the moment, I can control it from anywhere in my flat, it makes beautifully wiggly lines:
Matt is using his as an [http://www.mattvenn.net/2011/09/19/polargraph-energy-monitoring/ energy monitor]; I'm not sure what mine is going to do yet.
The basic code is on Matt's GitHub [https://github.com/mattvenn/arduinosketchbook/tree/master/energyplotterPolar here] and the circuit layouts are
(I'll post my modifications once I've tidied it up a bit)
The circuit is an AVR board, with a chip to drive the steppers and some cunning power supply work. For the bluetooth, I"m using a Roving Networks RN41 module, which gives a serial over bluetooth link. Please excuse the slightly dodgy soldering!
* 29 -> GND
* 11 -> +3.3V (using a regulator down from the 5V supply to the AVR
* 14 (UART TX) -> IO 3, via a 10k resistor (as suggested [http://jarkman.co.uk/catalog/robots/sketchy.htm here]
* 13 (UART RX) -> IO 2, via a 2:3 volatage divider to turn 5V into 3.3v
* 21 -> GND via an LED to show status
* 4 -> +3.3V to force 9600 baud rate (it talks to the AVR using a software serial link, which doesn't like working at 115200)