Construction date: November 20th 2014 to March 20th 201520150311_131524

Cost: 600 dollars, less with change in battery type. Each robot was about 170.00 dollars.

Time to build: 15 hours

Status: Completed





This Pixybot project started shortly after I joined a hacker/maker space in downtown Saint Louis. The space is called Arch Reactor, and it has been a great place for me to bounce ideas off of other people with similar interests and knowledge. They have a wide selection of tools available for use, including a TAZ 3D printer and a 80 watt laser cutter.

These robots are built around the Pixy computer vision sensor. This vision sensor is low cost for under 100 dollars. The sensor tracks color hues at a whopping 50 frames per second.  If you’re interested, you can find more information about Pixy at their wiki page. This project sprang up from the idea that Arch Reactor members often go to event to get the community involved  in making and repairing. I thought robots would be a nice way to draw individuals to the table, and get them interested in robotics, would be an interactive display.  This display would feature three robots that could track colored balls on a transportable table. To create this project I filled out an Arch Reactor Awesome Grant and I was awarded the grant by Arch Reactor to build the robots. It was easy to apply, and I encourage more members to do so. I am so grateful for the Awesome Grant as this project would be outside my budget without it.

Below is a link to the related documents for this project.
Grant proposal

Features include:

  1.  Velcro attached battery packs for quick swapping out and charging
  2.  Li-ion battery packs rated at 2800mAH at 7.2 volts. They are some good cells that peak at around ~8.4volts
  3.  Clean look with translucent white added wire management guide
  4.  Arduino controller for an overall cheap design to build
  5.  3D printed parts to show off what can be done with the relatively new technology
  6.  Soft rubber Lego tires for a much grippier robot.  (It’s a word)
  7.  Tons of left over prototyping space on the Arduino prototyping shield
  8.  Pixy is programmable on the fly and takes only a few seconds to train to a new color
  9.  Built-in, easy to grip handle to make picking up the robot easy
  10.  Internal sensor to monitor battery pack voltage level
  11.  Pause button to allow for reprogramming the Pixy on the fly
  12.  Front mounted IR sensors to allow obstacle avoidance

Below is a link to a separate page that contains a construction guide for the robot you will find .stl 3D model files and the current code for the robot

Pixybot Construction Guide

Below is a shot of my ESD table while building on the robots. The wheels are Lego wheels that have be epoxied to servo hubs. I could not find any better wheels for the price.



Below is a video of one Pixybot following another chasing a orange ball. Enjoy the video!

Things I may do differently on the next version:

  1. Buy a 3D printer to help speed up the build of the robot. I found that using a community 3D printer really slowed down the the prototyping process, as well as the final product.
  2. Further the design of a usable wheel in the future would drive down cost. Lego wheels work great, but they are expensive and can be hard to find.
  3. Adding a Arduino with a Bluetooth module would be great once the price drops a little further.
  4. I attempted to add battery protection to the Li-ions. I could not get current flow out of the modules purchased from Tenergy.
  5. Adding a full pan tilt module to the robot would increase cost a bit, but I think it would help with human interaction and greatly improve the tracking of the robot as a whole.
  6. Design a way for the robot to squint in full sun light and/or calibrate with an external light sensor. This would help in multiple lighting situations that the robot may encounter.
  7. Further reduction in overall size worked very well for the goal of these robots. I would like to try attaching a Pixy, with updated firmware, to a full sized 330mm base with reduced motor speed.

In the slideshow below are some concept pictures of the robot made with Google sketch-up pro. There are also a few pictures of the build process.

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