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Pololu 3pi Robot

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.

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	Description		Specifications (10)		Pictures (19)		Resources (21)		FAQs (8)

…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. R. Steven Rainwater, robots.net

Note: The LCD bezel on the 3pi robot is changing from silver to black. Once the stock of silver-bezeled 3pis is sold, 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 and featuring 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.

The diagrams below highlight the important features of the 3pi. Click on either picture for an expanded view.

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. We offer a combination deal that includes a 3pi robot, USB AVR programmer, and USB cable.

The 3pi is powered by 4 AAA batteries, which are not included. We recommend rechargeable NiMH cells, which may be purchased from Pololu or at a local store carrying electronics.

Optional Accessories

We currently offer 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.

3pi Robot Video Gallery

The following videos from Pololu and our customers show some of the things you can do with the 3pi robot. The first video in the playlist introduces the 3pi’s basic features and operation.

The second video shows a 3pi prototype autonomously solving a line maze, first by exploring the maze and then by running the learned shortest path from start to finish, and the third video shows six 3pi prototypes simultaneously participating in a line-following exhibition at a local robotics competition (last one remaining on the line wins!). Please note the 3pis in the last few videos are using additional hardware for things like RC control and obstacle detection.

The above videos (with descriptions) and more can be found on our 3pi videos page. These videos show many more things that you can do with the 3pi, including RC control, following a laser pointer, wall following, solving looped mazes, and driving around line courses with kinks, gaps, and obstacles. Check out what some of our customers have done with this amazing little robot and get inspired!

Note: Since June, 2009 (starting with serial number 0J5840), 3pi robots have been shipping with the newer ATmega328P microcontroller instead of the ATmega168 that was on original units. 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 instead of 16 KB flash, 1 KB RAM, and 512 bytes 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).