Common sensors on smartphones

Android OS 11 sensor introduction

In the Android2.3 gingerbread system, Google offers 11 types of sensor supply layer usage.

#defineSensor_type_accelerometer 1//Acceleration#defineSensor_type_magnetic_field 2//Magnetic#defineSensor_type_orientation 3//direction#defineSensor_type_gyroscope 4//Gyroscope#defineSensor_type_light 5//Light Sensing#defineSensor_type_pressure 6//pressure#defineSensor_type_temperature 7//Temperature#defineSensor_type_proximity 8//Close#defineSensor_type_gravity 9//Gravity#defineSensor_type_linear_acceleration 10//Linear Acceleration#defineSensor_type_rotation_vector 11//rotation Vector

Let's look at these 11 sensors in turn.

1 Acceleration Sensor

The accelerometer is also called G-sensor, which returns the acceleration values for the X, y, and Z axes .

This value contains the effect of gravity, in units of m/s^2.

Put your phone flat on the desktop, the X axis defaults to the 0,y axis default 0,z axis default 9.81.

Place your phone face down on the desktop with a Z axis of-9.81.

Tilt the phone to the left and the x-axis as positive.

Tilt the phone to the right and negative x-axis.

Tilt the phone upward and the y-axis is negative.

Tilt the phone downward and the y-axis is positive.

The accelerometer is probably the most sophisticated MEMS product, with a wide range of accelerometer sensors on the market.

The commonly used accelerometer in mobile phones is Bosch's BMA series, AMK 897X series, St's LIS3X series, etc.

These sensors typically provide an acceleration measurement range from ±2g to ±16g with an I²C or SPI interface connected to the MCU with a data accuracy of less than 16bit.

2 Magnetic Sensor

The magnetic sensor is referred to as m-sensor and returns the environmental magnetic field data of the X, y, and Z axes .

The unit of the value is micro-Tesla (Micro-tesla), expressed in UT.

The unit can also be Gauss (Gauss), 1tesla=10000gauss.

There is generally no independent magnetic sensor on the hardware, and the magnetic data is provided by the electronic Compass Sensor (E-COMPASS).

The Electronic Compass sensor also provides direction sensor data for the following.

3 Direction Sensor

The direction sensor is abbreviated as O-sensor, which returns the angle data of the three axes, and the unit of the direction data is the angle .

To get accurate angular data, e-compass needs to get g-sensor data,

The production o-sensor data is calculated, otherwise only the horizontal angle can be obtained.

The direction sensor provides three data, azimuth, pitch, and roll respectively.

Azimuth: Azimuth, returns the angle of the magnetic north and Y axes at horizontal time, ranging from 0° to 360°.

0°= North, 90°= East, 180°= South, 270°= West.

The angle between the pitch:x axis and the horizontal plane, ranging from -180° to 180°.

When the z axis rotates toward the y axis, the angle is positive.

The angle between the roll:y axis and the horizontal plane, for historical reasons, ranges from -90° to 90°.

When the x-axis moves toward the z-axis, the angle is positive.

The electronic compass needs to be calibrated before it can get the correct data, usually with a 8-word calibration method.

8-word calibration requires the user to do 8-word shaking in the air using a device that needs to be calibrated,

In principle, as much as possible, the device normal direction points to all 8 quadrants of space.

The electronic compass chip used in the mobile phone has the AKM company's 897X series, St company's LSM series as well as Yamaha company and so on.

Because of the need to read g-sensor data and calculate m-sensor and o-sensor data,

So vendors will generally provide a background daemon to complete the work, electronic compass algorithm is generally the company's private property rights.

4 Gyro Sensor

The gyroscope sensor is called gyro-sensor and returns the angular acceleration data for the X, y, and Z axes .

The unit of angular acceleration is radians/second.

Measured by Nexus S mobile:

Rotate horizontally counterclockwise and the z axis is positive.

The horizontal counterclockwise rotation, the z axis is negative.

Rotate to the left and negative on the Y axis.

Rotates to the right and the y-axis is positive.

Rotate up and the x axis is negative.

Rotate downward and the x axis is positive.

ST's L3G series of gyroscope sensors are popular, iphone4 and Google's Nexuss use this kind of sensor.

5 Light Sensing Sensor

The light sensor detects real-time light intensity, the unit of light is lux, and its physical meaning is luminous flux on the unit area.

The light sensor is mainly used for the LCD auto-brightness function of Android system.

The brightness of the LCD can be adjusted in real time according to the light intensity sampled.

6 Pressure sensor

The pressure sensor returns the current pressure in the unit of Hectopascal (HPa).

7 Temperature Sensor

The temperature sensor returns the current temperature.

8 Proximity Sensor

The proximity sensor detects the distance between the object and the phone, in centimeters.

Some proximity sensors can only return far and near two states,

Therefore, the proximity sensor returns the maximum distance to the far state, which is less than the maximum distance to return to the near state.

Proximity sensors can be used to automatically turn off the LCD screen when answering a phone to conserve power.

Some chips have integrated proximity sensors and light sensors for both functions.

The following three sensors are the new sensor types proposed by ANDROID2, and it is not yet clear which applications are available.

9 Gravity Sensor

The gravity sensor is referred to as gv-sensor and outputs gravity data.

On Earth, the value of gravity is 9.8, the unit is m/s^2.

The coordinate system is the same as the accelerometer sensor.

When the device is reset, the output of the gravity sensor is the same as the accelerometer sensor.

10 Linear acceleration Sensor

Linear accelerometer is referred to as la-sensor.

The linear accelerometer is the data obtained by the acceleration sensor minus the gravity effect.

The unit is m/s^2 and the coordinate system is the same as the accelerometer sensor.

The formula for acceleration sensors, gravity sensors and linear accelerometer is as follows:

Acceleration = gravity + linear acceleration

11 Rotation Vector Sensor

Rotary vector sensor for short rv-sensor.

The rotation vector represents the direction of the device, which is a mix of axes and angles to calculate the data.

Rv-sensor output of three data:

X*sin (THETA/2)

Y*sin (THETA/2)

Z*sin (THETA/2)

Sin (THETA/2) is an order of magnitude for RV.

The RV is in the same direction as the Axis rotation.

The three values of the RV, together with the Cos (THETA/2), constitute a four-tuple.

RV data has no units, and the coordinate system used is the same as acceleration.

Example:

Sensors_event_t.data[0] = X*sin (THETA/2)

SENSORS_EVENT_T.DATA[1] = Y*sin (THETA/2)

SENSORS_EVENT_T.DATA[2] = Z*sin (THETA/2)

SENSORS_EVENT_T.DATA[3] = cos (THETA/2)

The values for GV, LA, and RV are not available in the physical sensor directly,

G-sensor, O-sensor, and gyro-sensor are required to be calculated by the algorithm.

The algorithm is usually the private property of the sensor company.

The concept of sensors

For sensors, science and engineering are not unfamiliar. The national standard gb7665-87 defines the sensor as: "A device or device that can feel the specified measurement and converted to a usable signal according to a certain law, usually consisting of a sensitive element and a conversion element ". Like our corridor of voice-activated lights, digital cameras and other sensors, and even the mobile phone itself is a conversion of the sound into digital signals in the transformation of the sensor, its range is too wide,. And the small part of the summary here are some of the mobile phone in the state or environment, into the device to change the state of the mobile phone (of course, in this small series on almost every cell phone, such as cameras and other sensors).

The role and significance of sensors
Today's smartphones are more than just mobile-phone performance hardware, and the new generation of smartphones is also more interactive in the sense of experience and user interaction than in a CPU-like configuration. At present, the application software ecosystem of smart phones is expanding, and the sensors are necessary to interact with the user. Sensors make users more fascinated with application software. Apple, the benchmark for a new generation of smartphones, is also a leading player in this area. (Think of the time when Nokia had no big touch, the WM-system phone was still poking its fingers, and the iphone generation's capacitive screen, which zoomed in and out, made a lot of people drool.) Yes, the small part did not write wrong, capacitive screen is also a sensor)
In fact, the ecosystem of smartphone application software is expanding. In addition to the sensor can increase the sense of expression and user interaction these conceptual things. The application of the sensor on the game also becomes the new development direction. Just as the somatosensory device is rising in the game, the sensors will grow faster on mobile phones and tablets. Sensors are now used in games, health care, physical training, and many new applications.
Thanks to the addition of sensors to smartphones, smartphones are becoming smarter. The acceleration sensor responds to the user's interaction by making the traditional, mundane input work a novel experience similar to a game, thereby increasing the user's willingness to use smart phones. In the past, the focus of smart phone comparisons is whether to have an accelerometer, which is now becoming more mobile with a three-axis gyroscope, in the future there will be more new sensors to join.




The following list of people are more concerned about the common several sensors

Gravity sensor

Mobile phone Gravity Induction technology: The use of piezoelectric effect, in short, the measurement of a piece of heavy (weight and piezoelectric film into one) gravity orthogonal two-direction of the force of the size, to determine the horizontal direction. Through the force-sensitive sensor, feel the mobile phone in the changing posture, the change of center of gravity, so that the mobile phone cursor change position to achieve the function of choice.
Mobile phone gravity sensor refers to the mobile phone built-in gravity stick chip , support for shaking switch the required interface and functions, shake the screen, flip mute, swing switch video, etc., is a very fun to use the function.
Gravity Sensor said the simple point is that you put the phone in the hand is vertical, you will it to 90 degrees, cross over, its page will follow your center of gravity automatically response, that is, the page also turned 90 degrees, very humane. Now basically smartphones have built-in gravity sensors, and even some non-smartphones have built-in. Its common application has played the balance ball, as well as horizontal screen to browse the Web, read novels and so on.

Acceleration Sensor
An accelerometer is an electronic device capable of measuring acceleration forces. Acceleration is the force that acts on an object as it accelerates, like the gravity of the Earth. The acceleration force can be a constant, such as g, or it can be a variable. So the range is larger than the gravity sensor, but in general the accelerometer is referred to as a gravity sensor, so the two can be considered equivalent.

Directional sensor

A cell phone direction sensor is a component that is installed on a mobile phone to detect the orientation of the phone itself, rather than the function of a compass that is generally understood.

Mobile phone direction detection function can detect the phone in the upright, inverted vertical, Zoo, right horizontal, tilt, bent state. The mobile phone with direction detection function is more convenient and humanized. For example, when the phone is rotated, the screen image can automatically rotate and toggle the aspect ratio, and the text or menu can be rotated at the same time, making it easy for you to read and listen to MP3. Someone might say, "Is this the same as that gravity sensor?"
The two are not the same, the direction of the sensor or the application of angular velocity sensor is more appropriate, the general mobile phone on the direction of the sensor is sensing the horizontal plane azimuth, rotation angle and tilt angle. If you think it's a bit of a theory, give me an example. There are directional sensors that can play the city racing game very well. And only gravity sensors can play, but yes, it's very confusing.

Tri-Axis Gyroscope
Tri-Axis Gyroscope: The position of 6 directions is measured simultaneously, moving the trajectory, accelerating. A single axis can only measure the amount of One direction, that is, a system requires three gyroscopes, and a 3-axis one can replace three single-axis. The 3-axis is small in size, light in weight, simple in structure and good in reliability, and it is the development trend of laser gyro. For the laser gyro is more used in military aspects, we do not discuss. But we can see that the iphone 4 application of the tri-axis gyroscope is more advanced.
If the gravity sensor can be measured by a straight line, the sensor is measured by the plane, then the three-axis gyroscope measured direction and position is three-dimensional. Especially with some of the first-person shooter games like Rainbow Sixth, you'll find that the effect of a triaxial gyroscope is obvious.

Distance sensor

Distance sensor is a kind of sensor that uses measuring time to realize distance measurement, and to detect distance of object. Working principle: By emitting a particularly short light pulse, and measuring the light pulse from the emission to the object reflected back from the time, by measuring the time to calculate the distance between the object. The purpose of this sensor on the phone is when we call, the phone screen will automatically turn off, when your face left, the screen automatically open, and automatically unlocked. This is quite useful for smartphones with a shorter standby cell phone. Now many smartphones are equipped with this sensor.

Light Sensors (inductors)

A light sensor, or photoreceptor, is a device that adjusts the brightness of the screen according to the brightness of the surrounding light. is in the light of the place the phone will automatically turn off the keyboard lights, and slightly enhance the screen brightness, to save energy and better watch the effect of the screen, in the dark place automatically turn on the keyboard lights. Can be adjusted to switch off in the tool settings. This sensor also mainly play a role in saving the power of mobile phones, after all, the current smartphone standby time is very headache, can save on it.

Electronic compass, also called azimuth Sensor (sensor)
An electronic compass, also known as a digital compass, is a way to use the geomagnetic field to set the Arctic. Known as compass in ancient times, the modern use of the magnetic resistance sensor produced by advanced processing technology for the digital Compass to provide a powerful help. It is now generally useful to use a magnetoresistive sensor and a magnetic flux gate to process an electronic compass. This is the electronic version of the compass, with GPS and map is very easy to use, not the whole disoriented.
Of course, in addition to these more common sensors, on female mobile phones can see ultraviolet sensors, on the military phone can see the pressure and temperature sensors and so on.

In the 2011, the development of smartphones can be described with speed, with all the new technologies. Last year's E3, whether it's smartphones, Sony PSV or Nintendo's Wii U consoles, have a lot in common with hardware configurations. such as gravity sensing, triple gyroscopes, accelerometers, and so on. So what's the effect of these familiar and unfamiliar technologies? In this article, I will take you to inventory and mobile phone sensor related things, let us fully understand these interactive technology.

At this stage, smartphones have ushered in their new era. In fact, a few years ago, there was a gravity sensor. Now, looking at mainstream smartphones, gravity sensors have become standard for many mobile phones. In the application of the more ingenious, which contains the screen automatically rotate, shake a shake to find friends, a variety of song-throwing operations. In the mobile game is also endless. In the iOS and Android platforms, most games use gravity sensors. such as the need For Speed series, the modern War series and so on. This new gameplay obviously brings a fresh experience to the user after leaving the traditional single touch-only operation.

The world's thinnest accelerometer

In June 2010, the first smartphone to carry a triple gyroscope, the iphone 4, was officially released. iOS has always been one of the best platforms for mobile gaming. In the iphone, we play games in a variety of ways, virtual joystick, touch operation, gravity sensor, voice control, camera, etc. can be used for controlling the game. Since then, Meizu MX and other Android-powered smartphones have also successfully joined the triple gyroscope technology. At the same time, the software and games that support the triple gyroscope are growing. The presence of sensors such as gravity sensors and gyroscopes has fully enhanced the player's experience, shortening the distance between reality and the virtual world.

The so-called electronic sensor, in fact, refers to the ability to detect and feel the external signal, light, heat, temperature and other physical devices. Let's take a look at the five types of sensors common in mobile phones.

Gravity sensor

First, let's look at what gravity-sensing technology is. It is achieved by the use of piezoelectric effect, by measuring the internal weight of a piece of gravity orthogonal two direction of the size of the force, so as to determine the horizontal direction. In smartphones, the system defaults to the center of gravity sensing when the phone is placed horizontally. In reality, however, it is difficult for a player to maintain a horizontal posture while operating. Therefore, generally in the game settings, there will be a set function, let the player choose their own holding state of the center.

Tablet PC with gravity sensor technology

Most smartphones now use a combination of g-sensor gravity sensor + tri-axis accelerometer. If you use only the G-sensor phone, you can only tilt 90 degrees, and can not rotate 360 degrees.

Three-axis MEMS accelerometer

A three-axis accelerometer is another output sensor on the phone. The inclination of the device relative to the horizontal plane can be calculated based on the acceleration generated by the gravitational induction. As a result, the technology is often confused by people and gravitational induction. Actually there are some obvious signs to distinguish them. First, the MEMS triaxial accelerometer can perceive gravity, the static posture of the cell phone, and the direction of motion. Second, a mobile phone screen with an accelerometer rotates with different angles of intelligence. In addition, the music player software is popular for song-throwing features, chat software shake-shake function is also based on the accelerometer. Of course, the game also takes full advantage of this feature. For example, drift triggering in racing games.

3D Azimuth Sensing Device

Electronic Compass

An electronic compass is a feature of a magnetoresistive sensor applied to a mobile phone. Although the mobile phone can be located by GPs. But how do we perceive the position when the GPS signal is not good or there is no network? The electronic compass function, which has been popular in recent years, can judge the Cardinal. And all of this is distinguished by the Earth's magnetic field. It can also be used to act as a compass navigation in critical situations.

The electronic compass used in the mobile phone

FPS Game required Triple gyroscope

Since the first introduction of the gyroscope in the 2010 iphone 4, mobile gaming has changed dramatically. Prior to this, gyroscope technology was more used in helicopters, the flight can fully maintain balance. The presentation of smartphones and games is mainly due to the development of semiconductor technology for MEMS applications. It is a miniature machining technology capable of making very small mechanical structures. Overall, MEMS tri-Gyroscope and MEMS triaxial accelerometers are characterized by precision, compactness and low cost.

Use the triple gyroscope to aim and shoot

Briefly introduce the concept of gyroscope. Gyroscope is a device for measuring or maintaining direction, based on the principle of conservation of angular momentum, can judge the relative position, direction, angle and level of the object in space. Finally, according to the user's action output corresponding instructions. Let's take a look at a few practical examples. The famous game Modern Warfare 3 is the ability to rely on a gyroscope for targeted shooting. When the gyroscope is turned on, it means that we need to keep turning the body to operate.

Gyro makes the game more realistic

Light distance sensor

Let's look at the light distance sensor on the phone. Light sensing in a cell phone is achieved using a light sensor. is generally designed on the sensor screen, by identifying the strength of the outside light in the display effect to make adjustments. Using the sensor, the most obvious example is the mobile phone automatically sensing the surrounding environment, so that the screen brightness automatically adjust.

Light sensor above the phone

The distance sensor is also known as the displacement transducer. Operation can be achieved by sensing the distance between the sensor and the object. In general, the distance sensor is near the handset, when we answer or make a call, the distance sensor can be measured by the distance between the ear and the handset to enable the screen display of the automatic opening and closing, and ultimately can effectively save power.

Summarize:

The author believes that the future mobile phone terminal touch + body sense of operation will be a major trend, and the naked eye 3D technology in the future may also be combined with various types of sensors. With smartphones and tablet sensors developing in the direction, it's not difficult to combine them. The advent of sensors allows people to interact more realistically with electronic devices such as mobile phones. We are also pleased to find that there are more and more software applications that support the operation of triple gyroscopes, accelerometers, and more. In the early 2012, we also look forward to the mobile terminal operation can be more diversified, more arbitrary, and ultimately achieve a more perfect human-machine interaction.

Common sensors on smartphones