Apps and sensors

Apps and mobile devices

Sensors and SOCs (system on a chip) in a smartphone.

An electronic device converts signals from the environment (sound, light, heat ...) into electrical signals (voltages, currents ...). To "perceive" information from reality, an electronic device has sensors. A smartphone is one such example of an electronic device equipped with a whole host of sensors.

Unlike a website, an app you install on a mobile device can request access to file system information (for example, your photos, messages...), as well as access to the various sensors present. The app must seek approval for this, but few people bother to read all the terms of use.

Verschillen tussen een browser en een mobiele app.

Motion sensors

Motion sensors detect movement, acceleration and rotation along the three axes of the device's coordinate system. These are the sensors that allow your smartphone to measure the number of steps you take, the direction of your path and tilt when playing a game. Some examples of motion sensors are accelerometers, gravity sensors, gyroscopes, and so on. Every smartphone has a 3-dimensional coordinate system. Based on this system, sensors in your smartphone detect and record changes in real time. The X-axis runs along the width of the device. The Y-axis runs along the length of the device. The Z axis runs along the device.

Position sensors

Position sensors record the physical location of the device. They do this by identifying the phone's coordinates - taking the world around them as a frame of reference and its orientation in three-dimensional space. Phones use them for navigation, detection of screen orientation and more. Examples of position sensors include proximity sensors, GPS and magnetometers.

Ambient sensors

Environmental sensors detect important changes in your smartphone's environment. These include changes in lighting, pressure, temperature, adjusting brightness when auto brightness is on, screen temperature, measuring air pressure, and more.

Accelerometer

An accelerometer records the motion of your device along the three axes of the coordinate system. The X axis measures the motion of your device from left to right, the Y axis measures the motion along top and bottom (including gravity), and the Z axis measures the motion forward and backward.

The data obtained by measuring the motion of your device is used to calculate acceleration. This information is then used by apps to determine direction, orientation and speed. For example, a fitness app measures the direction and pace of your morning jog.

Gyroscope

A gyroscope measures rotation along the three axes of the device's coordinate system. It detects the exact measurement of your phone's rotation in radians per second. Simply put, an accelerometer measures linear motion and a gyroscope measures angular motion. Both combined enable features such as automatic rotation, and they are used for motion-sensitive games such as Temple Run or Asphalt 9.

Magnetometer

A magnetometer measures your phone's orientation based on the earth's magnetic field. This sensor is essential for navigation and compass apps because it helps your phone determine its direction and adjust the map accordingly.

GPS

Like a magnetometer, a Global Positioning System (GPS) is a sensor with antennas that aids in navigation. It continuously receives signals from satellites that help calculate the distance traveled and the location of your phone. When a signal is received, the GPS sensor records a location. Depending on the time difference between two signals, the distance is calculated. Navigation apps use both GPS and magnetometer to determine location and direction.

Ambient light sensor

Ambient light sensors measure the intensity of light around the device. These sensors detect the changes in brightness of the environment and record its intensity. When the automatic brightness feature is enabled, the ambient light sensor data helps to adjust the brightness of the screen according to the light in the room. Automatic brightness is a useful feature, but if you want to change the brightness manually, you can turn it off.

Proximity sensor

Proximity sensors detect how close a certain object is to your phone. A quick example of this is turning off your phone's screen when you pick up and answer a call. This helps save battery power and prevents accidental taps during phone calls. In this example, proximity sensors work by measuring the distance between the screen and your ear, and when the distance equals a set value, the screen turns off before your ear touches the screen.

Hall-sensor

A Hall sensor is much like a proximity sensor, but it detects changes in the magnetic fields around the device. When it detects a change in the magnetic field, it sends this data to the processor, which turns off the phone's screen. This sensor is specifically used to detect the magnets in flip covers. When you close the flip cover, the magnet gets close to the device and disrupts the magnetic field around the device. This causes the processor to turn off the screen. When the cover is open, the magnetic field returns to normal, and the screen turns back on.

Biometric sensors

Biometric sensors use physical characteristics for identification and are typically used for security purposes. Since physical characteristics such as fingerprints, irises and faces are unique to a person, using them for identity verification provides better protection. Some of the biometric sensors in your cell phone are:

Fingerprint Scanner:This sensor uses a capacitive surface to generate electrical signals based on the ridges of your finger when you place your finger on the scanner.
Iris Sensor:This sensor uses invisible infrared light to capture and detect the pattern of your iris.

Atmospheric sensors

Atmospheric sensors detect various aspects of your device's environment, such as atmospheric pressure, ambient temperature, humidity, etc. Atmospheric sensors include:

Thermometer:This measures the temperature of the device and its surroundings.
Barometer:This measures the air pressure in the environment. As pressure increases with altitude, the barometer identifies your altitude by comparing the pressure recorded on your phone with that of the nearest weather station.
Humidity sensors:These sensors measure the humidity of your environment. This measures the temperature of the device and its surroundings.

Camera, microphone, LIDAR

The camera and microphone are also essentially sensors, but they need little further explanation. Newer in this thread is a LIDAR scanner.

LiDAR stands for Light Detection and Ranging. It is a technique that allows a device to scan the environment to calculate distances to objects. In self-driving cars, it is often used in combination with other techniques, such as radar.

LiDAR uses tiny invisible lasers. By reflecting against an object, the device measures how long it takes for the light to be reflected. This is then used to calculate the distance to an object. Hence, this is also called time-of-flight (ToF): the time it takes for light to "fly" through the air. NASA also uses LiDAR for Mars landings.