Monthly Archives: May 2014

A Good Days Polargraphing

I first learned of polargraphing from either OllyR on or from seeing Sandy at the Edinburgh Mini Maker Faire in 2013. When I recently realised that I had the necessary parts (minus a few of the cheaper components) to follow in the footsteps of Sandy’s build I downloaded the files and 3d printed some sprockets (on MAKLab’s Ultimaker2) and laser cut motor mounts (my own design). Today I finished that all off by making a crude pen gondola (clear CD, cardboard tube and screws/nuts/washers).

Gondola and Super Goat

The first print was of a vector produced by one of the MAKLab volunteers (I didn’t have anything prepared and was busy setting up the polargraph so it fell on the volunteers to produce a vector drawing).

MAKLab M on Polargraph

Proven to be working the next logical step was to draw the MAKLab logo. In this picture you can see the two stepper motors mounted to the drawing board (acrylic mounts clamp to the board) and the Arduino and Motor Driver Shield are zip tied to the top. My laptop is on the right running the processing sketch, turning the vector drawings into gcode and sending them to the Arduino.

Spirograph on Polargraph

I downloaded SVG Spirograph (it was the first link for my google search) and promptly produced a spirograph (ideal for this setup since I don’t have a servo installed to lift the pen off the page). It was mesmerising to watch and drew some attention. I think it would be cool to add a “Spirograph of the Day” which automatically generates a new spirograph and draws them each day (same spirograph drawn all day whenever the paper is replaced and a button on a laptop pressed).

Time lapse of the plotter in action. Unfortunately I forgot to take a photo of the finished spirograph.

EDIT: Added a servo to lift the pen off the page and got a photo including the finished spirograph from the previous Saturday.

Spirograph and Pen Lift Servo

Produced another Spirograph, This one looked better part-way through but looks messy now. Timelapse at the end of this post shows it turn from good to great to messy.

Saturday Spirograph

We wanted to try drawing a picture so I selected a photo from my flickr vectorised in Inkscape and loaded into the Polargraph software. The result was great.

Polargraph Penguin

Time lapse of this Saturdays drawings:

Minishift from Arachnid Labs

While at this year’s Maker Faire UK I picked up a Minishift kit from Arachnid Labs. I had previously bought their circuit pattern cards which I make use of when teaching the Intro to Arduino workshop. I soldered up the kit in the evening I got back from Newcastle using the instructional videos (a few non-intuitive elements such as orientation of the LED array and remembering to put the screws in before the LED array). I struck an obstacle when I tried to install and use Arachnid Labs’ Python example and not having much experience with Python I’m clutching at straws trying to get it working.


Falling at the first hurdle. On Windows 7 I tried using pip found in the Scripts folder within my Python 2.7.3 installation to install minishift-python but it spat back ImportError: No module named resource.

In hunting for a solution I found that I hadn’t added C:\Python27\ to the Windows Environment Variable %PATH% and while I was correcting that I added %PYTHONPATH%. states that the resource library is for UNIX platforms. I got this far and having seen this on a few google results decided that perhaps this isn’t Windows compatible.



Moving to Ubuntu on my old laptop I followed the Arachnid Labs instructions but couldn’t get the daemon running nor could I use the python example program to directly write text to the display.

ImportError: No module named hidUbuntu Screenshot

I had a go at installing cython in order to install hidapi (can’t find the link that inspired me to try that route) but my abilities with linux are rather limited and I hit some roadblocks I couldn’t get past.

Trying python -m minishift.minishiftd -d 32 appeared to pass (no feedback to the contrary) but when I use curl -G http://localhost:8000/set –data-urlencode “text=Test” it responded with curl: (7) couldn’t connect to host.


I was able to test that the minishift itself works by connecting it to an Arduino (without the USB to SPI adapter) and running the test code provided by Gregory Fenton on his blog With this success I went on to reuse portions of Arduino code I’d used with a MAX7219 LED array to scroll some text (only to find that Gregory had gone on to do something similar and post it on his blog).