Just got a bluetooth enabled drawing robot working. It's based on Sandy Noble's Polargraph and code+circuits from 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:

Polar drawing bot wiggly lines

Matt is using his as an energy monitor; I'm not sure what mine is going to do yet.

The basic code is on Matt's GitHub here and the circuit layouts are here

(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!

Quick pinout:

• 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 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)