CurlyCart
About the CurlyCart
The CurlyCart is a hack of the Power Wheels Wild Thing we accomplished over a weekend. The Wild Thing is a great little cart that has two main wheels that each can go forwards or backwards, allowing you to do 360 degree spins in place. Even with one of us in the drivers seat, the cart can get going pretty fast, and is a lot of fun to play with (even for 20-year-olds...).
We decided, upon playing with the cart, that we would hack it to record and play back our motion. For example, if the driver went forward, turned around a few times, then went backwards, the cart would record all of this and allow the driver to continuously play back this motion. Much like Logo, CurlyCart can trace out complicated iterative patterns.
This project was inspired by Phil Frei's CurlyBot, which is a small, hand driven toy that can record and playback physical motion. Phil's project was inspired in turn by Golan Levin's Curly.
If you would like more information or have questions about CurlyCart, please email curlycart@media.mit.edu.
Creating the CurlyCart
what you need:
To create the CurlyCart, we ripped out all of the power wiring in the Wild Thing, and installed a custom controller board built around a PIC microcontroller. We programmed the PIC in PICC to record the cart's control switch positions every 1/20th of a second, and stored their values in a 256Kb memory chip. The memory chip gave us approximately 60 minutes of record time.
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The PIC and motor controller
boards |
Matt writing and burning
microcode |
Schematics for controller board
We then connected four motor output pins on the PIC to four motor controllers running at +12V. The high voltage was needed to drive the high current automotive relays that we used to switch on and off the motors. The stock +6V rechargeable battery was used to provide power to the wheel motors. This battery provides enough power for about 30-45 minutes of driving.
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Beginning to wire up the motors
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Two automotive relays wired up
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Matt and Dana testing the initial wiring
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Dana and Adam connecting
the motors |
We installed some blue and green LEDs and a push-button switch to allow the driver to go from normal mode to record mode (blue) and then to playback mode (green).
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Blue LED indicates record mode
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Green LED indicates playback mode
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We attached all of the circuitry underneath and below the seat of the cart, and wired up the 12V flashlight battery to motor controllers. We also spliced in the 6V stock battery to the motor relays, and added a small battery pack (4 AA size batteries) for power to the PIC--the stock supply provides intermittent power to the PIC whenever a motor is turned on which causes the PIC to reboot without warning (this can be fixed by using a power regulator and some capacitors, but we didn't have time).
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The underside
of the cart |
The motor controller board
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The electronics fully assembled
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A closeup of the PIC controller board
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We also added a master power switch to the back of the cart, plus a red LED to know that the power is switched on. We disabled the gas pedal, which is primarily a safety feature--the stock cart won't drive if the pedal isn't pressed--and difficult to operate for anyone over 4' tall.
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Main power switch and power LED
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In the end, the CurlyCart looks almost exactly like the Wild Thing.
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The final product
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Testing the CurlyCart
We successfully tested the CurlyCart once everything was wired up. The entire project took the four of us all weekend to complete (Friday night to Monday morning, with a normal amount of sleep each night!). The CurlyCart cost about $215, including the Wild Thing cart and miscellaneous parts from Radio Shack.
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Matt recording a motion
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Wesley in the Atrium
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Matt letting the
CurlyCart drive |
Adam, Matt, Dana, and Wesley
after a triumphant weekend |
After presenting the CurlyCart at a research lunch at the Media Lab, we took it for a spin in our atrium. Here are some videos showing the cart in action:
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CurlyCart with driver
(click to load QuickTime movie) RealMedia G2 also available |
CurlyCart without driver. Watch out!
(click to load QuickTime movie) RealMedia G2 also available |
The Future of the CurlyCart
Now that we have the CurlyCart built, we'd like to make further improvements:
Acknowledgements
We'd like to thank Fisher Price for donating the Wild Thing cart and the Things That Think Consortium at the Media Lab for supporting and sponsoring this project. We'd also like to thank the Sociable Media Group and the Personal Information Architecture Group, as well Josh Strickon, Ari Benbasat, the Responsive Environments Group, and Phil Frei and Golan Levin for inspiring us.