In this work preliminary results of the implementation of a service robot is presented. A service robot needs to recognize his environment in order to be able to navigate with freedom, and therefore a robot needs localization and mapping system in order for the robot to be able to perform different task such as searching and relocating objects. This work shows an inexpensive robot that was built with a Lego Mindstorms NXT kit. This kind of robots can be constructed in different morphological configurations due to the capacity of quickly assemble and disassemble. On the other hand the communication based on the Bluetooth protocol allows an efficient way of transmitting information between the robot and the computer; in this case the measurement of the distance from the robot to the wall, enables the creation of a map of the environment in real time. In this project the robot was programmed using Lejos, which enables efficient programming using the Java Virtual Machine. In this project the NXT set-up with the ultrasonic sensor to detect the distance to obstacles and to scroll using the wheel, use the SLAM shifting technique, using an adaptation of this to simulate the instinct of a rodent or wall follower, to move and explore in an unknown environment and simultaneously plot a sketch of the area explored.