Sunday, September 7, 2014

ArrBot Rally Day!

 We got to the end of the ArrBot class, and 6 ArrBots showed up for the rally!  Sadly, a seventh ArrBot was stuck in a meeting with its driver.

I'm really pleased with how everybody did.  We started off with a soldering class, raw plastic for the 3D printer, the literally cheapest parts we could find on the internet, and a partially finished prototype.

We printed the bodies, modified cheap 9 gram servos into continuous rotation units for power, and worked through some pretty tricky electrical problems.  Everybody make prints and modified the servos.  Most were able to run the tread test program.  There's a few that just need some radio work (much easier now that we've had a couple of successful units under our belt!), and that should be ready in the next week or two.

From the class comment forms the students seemed to like everything as well.  The hardest parts were the servo modification (honestly, a pretty challenging task with that size of servo) and the radio setup.  There was a bit of a time crunch as well.  In future classes we may schedule a class alternating with a lab so that there's no expectation of anybody having to work at home.  We'll also be better on differentiating between 3.3V and 5V requirements.  We needlessly burned some time having to work around that.
We'll continue to work on the ArrBot software.  I think it will be a useful contribution to various two-wheel and two-tread robots.  Some upcoming features:
  • gyro stabilized calibration
  • battle lights
  • onboard sound
  • Bluetooth control
  • ArrLang, the ArrBot robot control language

 We'll also continue to study the radio hardware. There's some interference problems with the Bluetooth, and we had to add a capacitor to the nRF units.

But the end resulting units worked well and were a lot of fun to drive around.  I definitely think that adding RC capabilities to educational robots is the way to go.

Notes to self for next session:

  • get all 3.3V pro mini's.
  • get switchable 3.3V/5V FTDI units instead of the FTDI cables, which were more expensive and not of particularly good quality.
  • get two FTDI units per student for ease of debugging radio communications.  This can be done with the cost savings of eliminating the FTDI cable.
  • get 20mm header pins, as they held into the breadboards much more tightly.
  • have students provide two USB "B" cables for the FTDI connector.
  • get a stock of male and female crimps and covers.
  • have students provide their own wii nunchucks.
  • investigate SMD resistors for servo modification use.

Here's some video of the rally: The first item is trailer-style, the rest are are more traditional EastBay RC style videos. If anybody's an expert at embedding playlists on blogspot please give me a call!

Here's a quick overview of both the ArrBot and ArrMote.

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