Since Microsoft launched its Kinect motion-detecting system for video games, hackers have been eagerly repurposing the $150 device. Garratt Gallagher, a robotics engineer at the MIT Computer Science and Artificial Intelligence Laboratory, used it to build a robot called the Bilibot that he is selling online for $1,200. The device, which is small enough for Gallagher to carry in his arms, can perceive its surroundings, move around, and manipulate objects. The Kinect is a key element, ­Gallagher says, because it can detect its environment just as well as a sensor that costs $5,000.

A. Kinect
The Kinect provides data on more than 250,000 points in three-dimensional space, at a rate of 30 frames per ­second, with color information included. With these “eyes,” the Bilibot can sense its ­surroundings at much higher ­resolution and accuracy than was previously ­possible without expensive equipment.

B. Custom Power Board
Fueled by a cheap lead-acid ­battery, this ­component determines where to direct power throughout the Bilibot. It sends energy to the Kinect and the computer that processes the data it ­produces, and it charges the battery that the robot uses to move.

C. Robotic arm
The Bilibot’s robotic arm uses motors that let it lift about three pounds, which is more than many hobbyist robots can handle. Its gripper is powered by motors originally used for vent blades in air-conditioning units; Gallagher was able to buy them as surplus parts.

D. Custom computer
The robot relies on a 3.1-gigahertz Intel i3 processor with integrated graphics. In addition, it has four gigabytes of RAM and a 160-gigabyte hard drive. Gallagher tested eight different computer platforms before settling on this configuration.

E. Robot Operating System
The software that controls the Bilibot runs on top of the open-source Robot Operating System. Users have contributed packages that allow a robot to recognize gestures, track motion, and perform similar tasks. ROS is maintained primarily by a research institute called Willow Garage in Menlo Park, California.

F. iRobot Create
At the base of the robot is an iRobot Create, which is essentially iRobot’s floor-cleaning robot, the Roomba, minus the vacuum. This device enables the Bilibot to move. It includes a bump sensor, four downward-facing infrared sensors, wheel-drop sensors, and a side-­facing infrared sensor to find walls and way points.