The simplest plotter possible?

Some simple code to drive...

Example Input path (made in the ipython notebook)

  python3 -i plotter.py
  >>> pl.draw_circle(pl.center)
  >>> pl.choose_file()

adafruit stepper kit (~20$)
Nema17 steppers (x2) 300ma, 12V (these suckers are barely up to the task but all the kit can drive.) (~10$)
2 ordinary SG 90 servos. (~5$)
a 12V power supply. (~5$)
A RaspberryPi (any sort) (~35$)

The adafruit ppl are pretty smart to use a cheap LED PWM controller to drive the Toshiba stepper controller in the hat. But the driver software was a bit rushed, like everything adafruit. If you use their stock packages, you can't use servo pin 15 for the lifters while using the steppers because the frequency of the PWM generator needs to be changed. Also the stepper library defaults to fully energizing both coils too often to try to maximize power/torque. In my setup this caused the steppers to overheat, lose steps (due to thermal resistance presumably) and fail because about a half an Amp of power was being dumped into each stepper. I hacked up about 3 separate repos worth of adafruit code to make one plotter_kit.py driver that works for this specific application. I commented out the double stepping etc. YMMV.

Connect the stepper hat to the pi's I2C pins (SDA, SCL) and 3.3,5V and GND pins.
Power the stepper hat as well, wire up your steppers.
write the servos data lines to the empty connector 15 on the stepper hat, and power them with the 5.5V and GND lines on the stepper board.
Starting with blank raspbian, connect to wifi and clone this repo.
enable I2C (req'd, "c.f. raspi-config")
Connect it to the internet.
sudo pip3 install -e .

It's easy to check the coil voltages with a multimeter. Don't exceed the 12 they are rated for.
If the resistance of your stepper is too low, the stepper hat will blink green, and stop driving.
Counterweights should be the smallest weight possible that rests the gondola about 13cm from the inter-cog line.

Some random python line-artifiers I wrote while on planes to make stuff like:

Name		Name	Last commit message	Last commit date
Latest commit History 59 Commits
images		images
lines		lines
3dProjections.ipynb		3dProjections.ipynb
Average Quaternions.ipynb		Average Quaternions.ipynb
Generative image art.ipynb		Generative image art.ipynb
LaserArt1.ipynb		LaserArt1.ipynb
LaserArt2.ipynb		LaserArt2.ipynb
README.md		README.md
dump.svg		dump.svg
hand.pkl		hand.pkl
hand_processed.pkl		hand_processed.pkl
jobbetter_bkn.pkl		jobbetter_bkn.pkl
laser_gcode.py		laser_gcode.py
lineifiers.py		lineifiers.py
plotter.py		plotter.py
plotter_kit.py		plotter_kit.py
setup.py		setup.py
svg_tools.py		svg_tools.py