This is my first ‘ible. It’s an Arduino-controlled Lego RC car using XBee units for the “RC” part. The idea was shamelessly stolen from sath02’s excellent ‘ible, attributed above. We began and finished the project over winter break 2012, and I’ve been sitting on these pictures for about a year, and have finally found some time to get them posted.
I won’t be providing a step-by-step instructional, but I will be highlighting what were some of our key challenges, and what our solutions were for them.
Here are the parts we used, in no particular order:
- LEGO Technic Dune Duster #8207
- LEGO Technic Power Pack #8720
- Arduino UNO R3
- Sparkfun Ardumoto Motor Driver Shield
- Sub-micro Servo ROB-09065 (Sparkfun)
- 2x XBee 1mW Trace Antenna – Series 1 (802.15.4)
- XBee Shield
- XBee Explorer USB
- Various terminals and cabling
- Miscellaneous LEGO bits (90% of the parts came from the kits, we just needed 2 or 3 pieces to fill in)
- 2x RadioShack 3 AAA battery holders
Most of the code was written by myself, and while I tried to pique my son’s interest in it, a lot of it was over his head, though I think he got the basics. He’s already been through the SparkFun Inventor’s Kit with me, so he knew the basics of circuits and motors and the like, the code work was just too tedious for him.
The one thing I took away from this, besides spending some quality time with my son and building something really cool, was not to underestimate what children can grasp at any age. Don’t let the “recommended age” guidelines put you off of introducing your kids to a learning experience like this. You’re planting seeds for a lifetime of discovery and innovation.
And with that, on to the good stuff.
Step 1: Powering the drive wheels
Step 2: Turning left and right
Step 3: Making Sufficient Autonomous Power
To power the project, we started with a 9v battery and a simple adapter, hoping to eventually go to a LiPo and save space and weight. We quickly figured out however, that with running the XBee, the Ardumoto, and the Arduino, their was simply not enough battery capacity in a 9v for more than 5 minutes or so. After realizing that LiPo did not fit the budget, stepping up to 6x AAA was the only option as I had to have 9v for the Technic drive motor, and 6x AA, while providing great capacity, would have radically altered the design. With perseverance, and a little help from my 8 yo LEGO Master, we were able to stretch the body, remount the electronics platform, and came away with what I felt looked much more substantial, even without the articulating rear suspension. The original design had been much closer to the look of the Dune Duster kit, but just did not provide enough space to carry sufficient power.
To make the battery pack, we bonded two RadioShack 3 AAA battery holders together using Gorilla Glue and wired them in series to get the needed 9 volts. The pack provides 30 minutes to an hour of run time, by which time it has smacked into the cabinets, or has run afoul of the cat, and is in need of R&R anyway.