Category Archives: Robot

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:

Android Controlled Tank

At work someone mentioned using a robot to distribute the Friday afternoon sweeties and I accepted the challenge. Already having a tank remotely controlled with a PS3 Controller I decided it would need a camera to see where it’s going. Having recently upgraded my phone I was able to use the old one with IP Webcam to share the camera feed over wifi.


When I stumbled upon a brief article on Let’s Make Robots about a LEGO robot with a wifi camera which is controlled by a custom Android App. I followed the instructions on the website linked in the article and had the proof of concept up and running with the free version of the app. Upon buying the Pro version of the app I was able to drive the tank around via bluetooth and simultaneously see the camera footage from the old phone over WiFi.


My configuration takes a Heng Long 1:32 scale Bulldog Tank base (chassis, motors, gearbox and treads) driven by a Dagu 4-channel motor controller (over the top in this instance but a common item now found in three of my robots) and controlled by an Arduino MEGA ADK (also over the top but I was using this for the USB Host aspect when the tank was operated by PS3 controller via bluetooth dongle). The bluetooth dongle has been replaced with a Bluetooth module for a simple serial link.

The Bluetooth module I have is only identified by the following address written on the back and the label BT_Board v1.1. Thankfully I didn’t need to do much to make it work, just wired up the power (VCC, GND) and plugged the Tx and Rx of the bluetooth module into the Rx and Tx of the Arduino (crossed over so Tx talks to Rx and vice versa).

Servo added and the Arduino code updated I can now tilt the camera using some buttons on the BTBotControl interface.

A video has been uploaded to YouTube.

Where should I go from here?

  • Overhaul Arduino sketch to allow for joystick control of camera angle (like a pan and tilt mode where horizontal joystick moves will rotate the robot but vertical moves only raise or lower the camera).
  • Perhaps mount an Airsoft BB gun (I have the original one from the tank turret).
  • Write my own custom Android app? Try piping control of the robot through the on-board Android phone, doing away with the mix of Bluetooth and WiFi. While I’m at it make more use of the Android, it has GPS, an accelerometer etc.
  • Reversing view using phone’s second camera? Phone orientation means the rear-view camera is hidden in the holder.