Mad not-quite-HATting

With space at a premium in this year’s bot (it amounts to a squared-off Pi):

Pi overlaid with a square, showing the size of the enclosure

and because I fancied having a go at it, and, Lance had his hands full with the CAD work, we decided to design a custom PCB. It’s now on its way to us from Shenzen 🙂

Picture of our boards in bubble wrap
The board house sent us a photo when they finished production, which was a nice touch

The custom PCB needed to combine several functions that were separate boards and breakouts last year:

  • I2C mulitiplexer
  • propeller microcontroller for interfacing with the motor drivers/encoders
  • connectors for all the peripherals (IMU, motors and distance sensors)

along with some new functions that we wanted to squeeze in (screen and voltage sensors to monitor the batteries, for example).  I also thought it’d be a good idea to add some isolation and level shifting chips to the design so that we could better isolate the motors and support having noisy and clean power supplies.  Previously, we’d had gremlins that we thought might be down to noise and brownouts caused by the motors.

Since it’s pretty much the only game in town for open source PCB design (and Lance and I had used it before), we used Kicad to draw the schematic and then design the board itself.

We’ll cover a  bit more detail on the design in the next few posts but, if you are interested in making your own board, my number one tip is to punch “Kicad” into Youtube’s search box.  There are great how-to videos on there that guide you through the whole process.  My second tip is to search for “Kicad push and shove”; which will show you how to use the automatic layout tools.

Note about the title: while it fits on the Pi, our board isn’t a HAT because there are rules about what makes a HAT 😛  also, we’re mad to try soldering some of the chips we plan to put on there; they’re tiny :-O





PiWars 2019!

It was awesome to hear the launch of PiWars 2019 and we loved the space theme.  That led to a week of lunchtime brainstorming – what famous space exploration robots are there?  We ended up discounting most those as being a bit too spindly to 3D print.  So what else could we do with the theme?  What robots are there in space films?  And Wall-E was the obvious winner:

  • tracked – so uneven ground would not be a problem
  • boxy – so shape should be printable

But: The PiWars rules limit the width of robots and Wall-E has a fairly square footprint.  And a big chunk of the width is taken up by the tracks.  So were we going to be able to fit all the electronics into the body?

That has turned into an interesting challenge.  We were fairly sure we were going to use similar electronics to last year, but we were also sure that we would have to reduce the size of them.  Which means designing a custom PCB…

So the challenges we’re going to face:

  • making it look like Wall-E – arguably the most important thing!
  • mechanical design – 3D printing tracks to look like Wall-E’s is going to be hard
  • making the electronics fit into the tiny body – ideally with extra servos to animate Wall-E  🙂
  • Finding places to mount sensors at the right height for the challenges
  • Figuring out how to mount the attachment hardware
  • Plus all the unexpected stuff we haven’t spotted yet!