There are thousands of sensors on the market today. The mobile market for sensors alone exploded from 10 million units in 2007 to several billion in 2016. With the emergence of IoT, wearables, drones, health monitoring, autonomous cars and robots, some reports estimate around a trillion sensors will be on the market in 2020.
Despite explosive growth, there are five types of sensors that every maker should own: accelerometers, gyroscopes, magnetometers, barometers and proximity sensors.
How Does an Accelerometer Work?
An accelerometer senses acceleration along x, y and z axis, including gravity. An accelerometer can measure things like inclination, vibrations, free fall and shock detection, step detection, wake-up detection, even concussion force. These days, many applications want to track movement. When the first Wii was released, the accelerometer was a revolution. Ten years later, it’s almost a commodity.
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Accelerometer vs Gyroscope Sensor
An accelerometer is useful for variables dealing with pure acceleration, but if you want to measure speed or rotation—if you’d like to spin your robot, for instance—a gyroscope is necessary. The combination of a 3-axis accelerometer and a 3-axis gyroscope is called a 6-DoF (Degree of Freedom) motion sensor. These two sensors are enough for basics robots that are driven via a remote control. But if you’d like to know where your robot is going, you need a magnetometer, also called an e-compass.
What is a Magnetometer Sensor?
AMR (Anisotropic Magnetoresistance) technology is replacing more and more Hall-effect sensors in order to decrease current, but that alone is not enough for a drone to find itself in the 3D space. To sense a change in altitude, a barometer is the only tool for the job. The mix of 3-axis accelerometer, 3-axis gyroscope, 3-axis magnetometer and a barometer forms a 10 DoF inertial sensor. A magnetometer is sensitive to external magnetic fields that can be created by the build design itself. It must often be placed in a specific area on a PCB that is suboptimal for the other sensors.
Barometer Sensor Working
A barometer requires a special package with a hole that can dictate its placement as well. Hence, a 10 DoF inertial sensor is often split into three packages: an accelerometer and gyroscope in one package, a magnetometer as the second package and finally the barometer. It’s possible to buy boards with these devices already mounted, like the 1604 from Adafruit. The ADIS16480 from Analog Devices is a complete 10- DoF inertial system that integrates automatic computations like an extended Kalman filter, for high end applications.
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Proximity Sensors
A system that integrates these four sensors will allow your robot to move as needed, but what if it needs to understand its environment? For environmental awareness, you need proximity sensors. The proximity sensor field boasts several new technologies. A magnetic sensor is well suited to detect the presence of metals within a short range and is widely used to prevent unwanted access to any sensitive or dangerous section of your robot. For longer range sensitivity, an IR proximity sensor is better, but IR reflection depends on materials and is not reliable to calculate distance. If your robot must be aware of the distance separating it from an object, time-of-flight technology or radar is best.
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These five categories of sensors are what will move your design today. Right now, image and audio sensor usage is more limited to specialists, but as open source libraries become more common, look to see widespread distribution of these technologies as well. One thing is for sure, as the sensor revolution marches on, there will be more and more ways to specialize your design.