Dexter Industries

The dFlex is the flexible sensor available from Dexter Industries. This sensor measures the bend of the sensor and records mechanical motion. dFlex is the newest product from Dexter Industries and is reviewed on several robotics blogs.[13]

For the temperature sensors, there are two versions: an open version and a protected version. The sensors come with a two meter long cord.[14] The temperature sensors are thermistor-based; they are read as an analog sensor by the NXT.

The dPressure sensor is made specifically for the Lego NXT Mindstorms system. It is capable of measuring up to 250 kPa (30 psi) and 500 kPa (70 psi) of pressure and gauge vacuum.

For the dSolar sensor, there are two 9V versions with different wattages: a 2W and a 4W model, both of which can power the NXT system or a user's robot. Dexter Industries also produces three additional adapters that relate to the solar sensor. The first is an optional capacitor bank that serves as a mini-battery; it provides continuous power for NXT projects if the system runs under a shadow or cloud. Second, there is an adapter that allows three solar panels to be plugged in simultaneously; this can provide up to 750 mA at 10 volts. The third adapter is a battery pack that can recharge the NXT battery pack utilizing solar power.[15][16]

The dGPS sensor provides GPS coordinate information to the user's robot and calculates navigation information. The sensor provides latitude, longitude, time, speed and heading to the user's project or robot. Since the LEGO NXT has limited computing capability and can't interface directly with a GPS module, the sensor includes a micro-controller and software that translates and checks the signal from the GPS, and also performs additional calculations and functions to aid navigation. The sensor can be used to build things like autonomous vehicles and mapping vehicles.[17]

The dGPS output data is compatible with Google Maps.[18][19] A miniature version of the Google Street View Car, which roams the streets to photograph them for Google Maps, was built by Mark Crosbie. He created his Street View car using Dexter Industries’ dGPS sensor to record coordinates and a small camera to take pictures as the vehicle drives down a street. The pictures from the camera can then be uploaded into Google Earth along with the coordinates. Using a KML format file, the Lego NXT can upload saved pictures, coordinates and data into a personal computer. Crosbie's miniature Google Street Car can show the path that the car drove, and also shows pictures taken along the way in Google Earth.[17]

An educational workbook for the dGPS, entitled "Beginning GPS with NXT Robots" was written and published by James Floyd Kelly in June 2011.[20][21] This book includes instructional projects with questions and descriptions that teach students about mapping, robotics, programming and navigational terms.[22] "Beginning GPS with NXT Robots" is an introduction to the basics of GPS, including hands-on activities and tutorials on how to use the features of the dGPS sensor in NXT robotic projects.[17]

According to Geocaching.com, "geocaching is a high-tech treasure hunting game played throughout the world by adventure seekers equipped with GPS devices. The basic idea is to locate hidden containers, called geocaches, outdoors and then share your experiences online."[23] By using the NXT and the dGPS sensor, the user is able to create a hand held GPS.[24] The accompanying dGPS geocaching software takes GPS coordinates of a target in decimal-degrees, references them against the coordinates of the NXT's current position, and then calculates the distance the NXT is from its destination as well as the compass angle. By turning the NXT hand held GPS in the correct direction according to the embedded compass, the user can reach the geocache. The software also allows the user to record the latitude and longitude to plot the user's journey in Google Maps.[25]

These NXTBee is a high-speed long-distance wireless communication sensor which allows a Lego NXT to communicate with any other device with an XBee radio. The NXTBee sensor makes the Digi XBee radio compatible with the Lego Mindstorms NXT system. The XBee 802.15 communication protocol is the wireless communication standard used by many robots and for inter-device communication. There are two types of NXTBees; the basic NXTBee can send information up to 300 feet away, and the NXTBee PRO can transmit or receive information from up to 1.2 km away. The NXTBee utilizes a high speed RS-485 line for high speed communication. The NXTBee uses the XBee protocol which can utilize both point-to-point protocol (PPP) networking and mesh networking.[26] Users can design a remote controlled car using the NXTBee.[27]

Carnegie Mellon University’s Robotics Academy developed a multi-robot swarm robotics project using the NXTBee and the Lego Mindstorms system. Swarm robotics is a popular topic in robotics because it coordinates numerous small robots to accomplish larger tasks. Swarm robotics using the NXT and NXTBee might be capable of performing complex tasks such as PID auto-straightening, thermal imaging and even line tracking.[28] CMU's Robotics Academy also teaches how to use the NXTBee at its advanced program training courses.[29]

The Thermal Infrared Sensor reads the surface temperatures of objects. It is a non-contact thermometer and does not need to be in contact with an object to measure its temperature. The sensor can read object temperatures between -90 °F and 700 °F (-70 °C and +380 °C). The sensor can read temperatures more than double the amounts other NXT thermometers measure.[30] The sensor has a high accuracy of 0.5 °C and a resolution of 0.02 °C. The Thermal Infrared sensor reads both the ambient temperature and the surface temperature of the object that the sensor is pointed towards. The sensor uses I2C protocol to communicate with the Mindstorms NXT.[31] The sensor can detect a flame at a range of 2 meters.[32]

Dexter Industries released the WiFi sensor called the dWIFI in November 2011.[33] The dWifi release was accompanied by a week-long instructional blogging campaign aimed at walking novices through the process.[34] The dWifi enables the NXT to transmit and receive information wirelessly between a computer and itself.[35] The sensor operates with standard 802.11 b/g/n access and can be configured to run on the vast majority of home networks. The Dexter Industries dWIFIs sensor connects to the NXT via the high speed communications Port 4 and is powered by an external 9V battery. The sensor comes with security options and is able to connect with WPA2-PSK, WPA, and WEP security networks.[36] Users of the dWifi can "tweet" information from the Mindstorms NXT to Twitter.[37][38] In February 2012, a dWiFi user released instructions on how to expand the range of the dWifi by using a High Gain Ariel.[39]

The Inertial Motion Unit (IMU) sensor combines an accelerometer and a gyroscope in one sensor. The sensor has six degrees of freedom, measuring x,y, and z axes for both the gyroscope and the accelerometer.[40] IMU users can create a "Segway" NXT, which enables a robot to stand on its tires and move in 360 degrees around its axis.[41] In conjunction with Lego Mindstorms' NXT Ultrasonic Sensor, the robot can be trained to simultaneously sense and avoid obstacles.[42]

The dCompass is a compass sensor for Mindstorms NXT.[43] This compact sensor detects magnetic fields for navigation and works on all three axis.[44] Using a magnetic sensor, the sensor is able to measure the Earth's magnetic field and returns a magnetic heading, showing which way your robot is heading.[45] The device can be used without calibration or, if needed, can be calibrated with software to account for magnetic fields to deliver a highly accurate compass heading.[46] The sensor is supported in NXT-G, Labview, and ROBOTC. The sensor communicates with the NXT via I2C and can be placed on any port.[45]