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Pololu 3pi Robot

Pololu item #: 975

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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.

Compare all products in Robot Kits or Robot Kits without Soldering or 3pi Robot and Accessories.

	Description		Specifications (10)		Pictures (16)		Resources (21)		FAQs (7)

...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

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.

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!

Our 3pi videos page shows many more things 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).