The Pololu 3pi robot is a complete, high-performance mobile platform featuring two micro metal gearmotors, five reflectance sensors, an 8x2 character LCD, a buzzer, and three user pushbuttons, all connected to a C-programmable ATmega168 or ATmega328 microcontroller. Capable of speeds exceeding 3 feet per second, 3pi is a great first robot for ambitious beginners and a perfect second robot for those looking to move up from non-programmable or slower beginner robots.

...the 3pi has been more thoroughly field tested than any other robot we’ve worked with. We’ve had way too much fun with this little robot and by the time you finish reading the review, you’ll probably want to buy one or two for yourself...

The 3pi robot is designed to excel in line-following and maze-solving competitions. It has a small size (9.5 cm/3.7" diameter, 83 g/2.9 oz without batteries) and takes just four AAA cells (not included), while a unique power system runs the motors at a constant 9.25 V independent of the battery charge level. The regulated voltage allows the 3pi to reach speeds up to 100 cm/second while making precise turns and spins that don’t vary with the battery voltage.

The 3pi robot makes a great platform for people with C programming experience to learn robotics, and it is a fun environment for ambitious beginners to learn C programming. At its heart is an Atmel ATmega168 or ATmega328P microcontroller running at 20 MHz. ATmega168-based 3pi robots feature 16 KB of flash program memory and 1 KB RAM, and 512 bytes of persistent EEPROM memory; ATmega328-based 3pi robots feature 32 KB of flash program memory, 2 KB RAM, and 1 KB of persistent EEPROM memory. The popular, free GNU C/C++ compiler works perfectly with the 3pi, Atmel’s AVR Studio provides a comfortable development environment, and an extensive set of libraries provided by Pololu makes it a breeze to interface with all of the integrated hardware. The 3pi is also compatible with the popular Arduino development platform. We provide a number of sample programs to show how to use the various 3pi components, as well as how to perform more complex behaviors such as line following and  maze solving.

1. Digital I/O lines and PD0 are available; two more analogue inputs and one analogue/digital pin can be made available by removing jumpers and disabling special features of the board.
2. Designed for use with 4 x AAA NiMH or Alkaline cells. A step-up regulator boosts the motor voltage to 9.25 V.