3pi Robot

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 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.

Note: The LCD bezel on the 3pi robot is changed from silver to black. All new units will ship with black-bezeled LCDs as shown in the main product picture.

Overview

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 ATmega328P microcontroller running at 20 MHz. The ATmega328-based 3pi robot features 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. Pololu provides 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.

The diagrams below highlight the important features of the 3pi.

For instructions on setting up and programming the 3pi, including sample code, contest ideas, and more, see the 3pi User’s Guide.

Required Accessories

An external AVR ISP programmer, such as our USB AVR programmer is required to program the 3pi.

The 3pi is powered by 4 AAA batteries, which are not included. We recommend rechargeable NiMH cells, which may be purchased from us (one of provided options) or at a local store carrying electronics.

Optional Accessories

Pololu currently offers two expansion kits for the 3pi that give you room to augment your 3pi with your own custom electronics. One expansion kit features cutouts that let you view the LCD below and allow you to reach the power button, reset button, and ISP programming header on the base. The other expansion kit has no cutouts and instead replaces the LCD, giving you access to more I/O lines and more prototyping space. These kits can be purchased with PCBs that have either black or red solder masks; the pictures below show the black versions.

A Video Introduction to the 3pi

To see for yourself what the 3pi is like, please take a look at the video below, which introduces its basic features and operation.

More Pictures and Videos of the 3pi Robot:

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!

Click here for even more 3pi videos!

Documentation and other information

Pololu 3pi Robot User’s Guide (Printable PDF: 3pi.pdf)

User's guide for the Pololu 3pi Robot.

Pololu AVR C/C++ Library User’s Guide (Printable PDF: pololu_avr_library.pdf)

Information about installing and using the C/C++ libraries provided for use with Pololu products.

Pololu AVR Library Command Reference (Printable PDF: avr_library_commands.pdf)

A reference to commands provided in the Pololu C/C++ and Arduino libraries for the AVR.

Building Line Following and Line Maze Courses (Printable PDF: building_line_courses.pdf)

Step-by-step instructions for building your own line-following courses.

Programming Orangutans and the 3pi Robot from the Arduino Environment (Printable PDF: orangutan_arduino.pdf)

Guide to making the Arduino IDE compatible with the 3pi robot and the Orangutan SV-168, Orangutan LV-168, and Baby Orangutan B robot controllers, including Arduino libraries for interfacing with the all of their on-board hardware.

Sample Project: 3pi Wall Follower (Printable PDF: 3pi_wall_follower.pdf)

Sample robot project for enhancing a 3pi robot to drive around objects on its left.

Sample Project: RC 3pi (Printable PDF: rc_3pi.pdf)

Sample robot project for making the 3pi radio controlled.

Application Note: Using the Motor Driver on the 3pi Robot and Orangutan Robot Controllers (Printable PDF: motor_driver_application_note.pdf)

Detailed information about the 3pi Robot, Orangutan SV-328/168 and LV-168, and Baby Orangutan B motor drivers, including truth tables and sample code.

3pi Robot Videos

Various videos of the Pololu 3pi robot in action.