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