The Roomba Red is approximately 13 inches (33 cm) in diameter and 3.5 inches (9 cm) tall. An external examination reveals the following parts:

Roombas run on a rechargeable NiMH battery. The Roomba Red battery pack is rated at 3 amp-hours and takes about seven hours to fully charge to about 18 volts. Some of the more recent Roomba models have cut that charge time down to about three hours. A full charge equals approximately two hours of cleaning time, which in the Roomba world means vacuuming three medium-size rooms before it needs to rejuice. The mobility system consists primarily of two motor-driven, tracked wheels. Roomba steers by alternating the power supplied to each wheel.

Roomba has a total of five motors:

• One driving each wheel (2 total)
• One driving the vacuum
• One driving the spinning side brush
• One driving the agitator assembly

In the following sections, we'll address each of the systems that make Roomba work, beginning with the most robotically interesting one: the navigation system.