The Pololu 3pi robot is a complete, high-performance mobile platform featuring two micro metal gearmotors, five reflectance sensors, an 8×2 character LCD, a buzzer, and three user pushbuttons, all connected to a C-programmable 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 Pololu 3pi robot is a small (9.5 cm/3.7" diameter, 83 g/2.9 oz without batteries), high-performance, autonomous robot, designed to excel in line following and maze-solving competitions. Powered by four AAA batteries (not included) and a unique power system that runs the motors at a constant 9.25 V, 3pi is capable of speeds up to 100 cm/second while making precise turns and spins that don’t vary with the battery voltage.

The 3pi is based on an Atmel ATmega328 microcontroller running at 20 MHz with 16KB of flash program memory and 1KB data memory. The use of the ATmega328 microcontroller makes the 3pi compatible with the popular Arduino development platform. Free C and C++ development tools are also available, and an extensive set of libraries make it a breeze to interface with all of the integrated hardware. Sample programs will be available 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. All this makes the 3pi a great platform for learning robotics!

Note: Starting with serial number 0J5840, 3pi robots are shipping with the newer ATmega328P microcontroller instead of the ATmega168. The ATmega328 is essentially a drop-in replacement for the ATmega168 with twice the memory (32 KB flash, 2 KB RAM, and 1 KB of EEPROM), so the 3pi code written for the ATmega168 should work with minimal modification on the ATmega328 (the Pololu AVR Library now supports the ATmega328P).

Note that an external AVR ISP programmer such as the Orangutan USB programmer is required to program the 3pi. 

General features of the Pololu 3pi robot, top view.

Labeled bottom view of the Pololu 3pi robot.

Specific features of the Pololu 3pi robot, top view.

The following video shows a 3pi prototype autonomously solving a line maze. It first runs through the maze executing a search algorithm, keeping track of which way it is turning at intersections and discarding paths that lead to dead ends. Once it finds the end, which is marked by a solid black circle, it determines from memory the best path from start to finish and on subsequent runs aggressively drives that shortest path. This is just one example of what the 3pi is capable of.

This unedited video shows six 3pi prototypes simultaneously participating in a line-following exhibition at a local robotics competition. The robots were all programmed independently. Last one remaining on the line wins!