Wesley Chan, Matt Lee, Adam Smith, and Dana Spiegel

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

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.

PICC code [html source zip]

The PIC and motor controller
Matt writing and burning

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.

Beginning to wire up the motors
Two automotive relays wired up
Matt and Dana testing the initial wiring
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).

Blue LED indicates record mode
Green LED indicates playback mode

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).

The underside
of the cart
The motor controller board
The electronics fully assembled
A closeup of the PIC controller board

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.

Main power switch and power LED

In the end, the CurlyCart looks almost exactly like the Wild Thing.

The final product

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.

Matt recording a motion
Wesley in the Atrium
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:

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:


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.

Last edited on 3/9/2001 by Dana Spiegel