Consumer electronics are growing faster each year. As a result, people have become more aware of how technology can assist them. One popular device that has been on the rise is an accelerometer and gyroscope. Microelectromechanical systems (MEMS) are becoming the critical element of these devices. They give the user a new way to interface with their device. They also detect the device’s motion and interact with it in new ways.
These devices are helpful for the consumer and industrial markets. They include the automotive and aerospace industries. Here, MEMS can sense motion in automobiles, ships, and aircraft. We can also use these sensors to sense speed and directions. It will increase the overall efficiency of these products. MEMS are helpful in airbag control units, side-impact airbags, and seat occupancy detectors. We also use them in smart cruise controllers in the automotive industry. An accelerometer and gyroscope are also beneficial in video game consoles. It is an example of consumer electronics. A microchip processes the information provided by this device before sending it to the console or a gaming platform.
What is an Accelerometer?
An accelerometer is a device used to detect the acceleration of a free-falling object. It consists of a mass, spring, and linkage. They suspended the mass from the linkage that one can replace from its rest position. If the object is accelerating vertically, the suspended mass will move opposite. The displacement of this mass measures how much acceleration the object is undergoing.
The accelerometer functions by detecting the acceleration of an object. We can use an accelerometer in many different applications. It is usually used by nature because some organisms use it to detect gravity or the earth’s gravity. Some scientific institutions use them to measure rotation rates and cosmic acceleration. Some forces cause these devices to work. They include Gyroscopes, Inertial Vector Indicators (IVI), MEMS, and Magnetometers.
How it works
An object is free-falling, and it is descending due to gravity. After a certain time, the object will reach a certain speed (this depends on the object’s weight). The acceleration due to gravity will be equal to g. A physical force then acts on the mass, causing it to decelerate. An accelerometer observes the deceleration. It measures the change of momentum caused by this force—this force changes when an accelerating force acts on it.
Piezoelectric effect:
An accelerometer also works with the effect of the piezoelectric effect. A crystal with bound atoms will create an electrical charge when you compress it. If you compress it, it will generate a voltage. The connection of this device will then cause it to work as an accelerometer.
Magneto-resistive effect:
An accelerometer is also composed of a magneto-resistive effect. It senses a small magnetic field. So, it detects the acceleration caused by magnetic forces.
Change in Capacitance:
In specific applications, an accelerometer works by measuring changes in capacitance. Thus experiencing a change in capacitance when it is free-falling. 2 capacitive plates are present. A coil and a capacitor connect them. The device observes the change in capacitance. We can use it to determine that an object is falling.
MEMS Accelerometers
Accelerometers depend on other operating principles. We use them in consumer electronics, automotive, and aerospace industries.
The accelerometer is one of the most popular MEMS devices. We can use it to detect vibration, shock, and small changes in the direction of an object. It is also a very efficient device since it requires little power when used. Therefore, you can leave it on for a long without draining the device’s batteries.
Microelectromechanical systems (MEMS) are the key element of accelerometers. They measure acceleration, rotation, and vibration. We measure the acceleration by the change in position of a proof mass. The proof mass is along with a resonant structure.
The most widely used type of accelerometer is the capacitive electromechanical sensor. Therefore, we also refer to it as an accelerometer.
Accelerometers are usually composed of a sensor chip and an integrated circuit. It has capacitors, inductors, and resonators (tuned circuits with resonant frequencies).
The sensor chip can be traditional CMOS, silicon-based CMOS technology, or other processes.
The device uses the effects of the piezoelectric effect to measure acceleration. The device observes the change in capacitance.
Applications of Accelerometers
We use accelerometers in a variety of applications, including:
1. Compass/Map applications:
In GPS navigation systems, Rayming PCB & Assembly use accelerometers to detect if the device is in motion. It will also detect which direction it is moving in. Through axis-based sensing, phones and tablets can determine their orientation and direction.
2. Tilt sensing:
Using a gyroscope, we can use an accelerometer to detect a device’s orientation. For example, iPhone uses an accelerometer and gyroscope. First, it detects when the user rotates the phone from portrait to landscape mode. Then, it changes applications accordingly.
3. Earthquake detection:
We use accelerometers to detect an earthquake. It also determines the magnitude of its movement.
4. Fall sensing:
We use accelerometers in advanced personal protection systems. They detect a fall and trigger life-saving technologies, for example, airbags and seat belts.
5. Medical devices:
We use accelerometers to detect a momentary speed of blood circulation. It also delivers critical information about the status of a patient. Artificial body parts, such as heart valves and hips, also have accelerometers. They help detect movement around the prosthesis.
6. Fitness trackers/wearables:
Accelerometers detect physical activity. This can detect if the user is walking, running, or biking.
7. Games and applications:
We use accelerometers to detect subtle movements during a game—for instance, the response time of a joystick controller.
8. In-car applications:
Accelerometers detect if the driver loses control of the vehicle. It then triggers an appropriate safety response.
What is a Gyroscope?
A gyroscope is a device that uses its natural inertia to measure the rate of rotation of an object. We consider it a mechanical effect. We use gyroscopes in geophysics space research and various electronics applications.
How it works
A gyroscope consists of two main parts:
A pair of weighted rings called gyroscopes
An angular rate sensor (usually called a magnetometer), which we do not use.
It works through the precession effect when a gyroscope rotates around one of its axes. It cannot detect the rotation angle when it is in an equilibrium position. But after its rotation, it will point up to the axis on which you placed it.
In this case, an inertial force acts upon the gyroscope. Since the angular momentum remains constant, extra kinetic energy will go with this motion. This force will make the gyroscope go backward. However, since nothing happens to the gyroscope, we call this the precession. Another precession effect is that a gyroscope will resist any change in its angular momentum until you apply torque.
The rotation rate of an inertial frame can measure the rate at which an object rotates in an accelerating frame. It does this through Einstein’s equivalence principle or Newton’s first law of motion.
Applications
We mainly use gyroscopes for navigation, flight control, and navigation in space exploration. However, they are also helpful for medical devices. An example is heart monitors and other medical equipment. Nuclear magnetic resonance (NMR) spectrometers also use gyroscopes to detect movement.
MEMS Gyroscope
The MEMS Gyroscope is also known as a Microelectronics-Mechanical System (MEMS) gyroscope. We use the MEMS engine in smartphones and cameras.
We use Gyroscopes in smartphones to enable image stabilization. It helps capture clear images while recording videos.
We also use it in drones that use MEMS technology. Even when the drone is not under direct human control, they enable flight control.
MEMS Gyroscopes are small miniaturized sensors. They use silicon chips, MEMS, and advanced processing technologies to achieve high precision. We use them in various applications, including gyroscopes, cameras, and navigation systems.
Applications of Gyroscope
In the past, we used MEMS gyroscopes in missions navigation systems. However, the application is expanding. Some of the notable ones include:
1. Consumer electronics through MEMS gyroscopes:
The demand for MEMS is rising in consumer electronics, particularly smartphones and tablets.
This is because most smartphones and tablets today come with a 3-axis gyroscope.
Gyroscopes can detect if a device is moving too much. For example, it would trigger an airbag system in an accident. If it detects a hard fall on the ground, it will call emergency responders using GPS.
2. Inertial guidance systems
Inertial guidance systems are essential in missiles, rockets, spacecraft, and UAVs.
The inertial guidance system can determine position and orientation in space.
3. Airplanes through MEMS gyroscopes:
A 3-axis MEMS module serves as an essential component. It enables the roll axis of a fly-by-wire (FBW) flight control system. This technology makes flying a jet at supersonic speeds possible for pilots.
4. Stability in vehicles, motorcycles, ships:
MEMS gyroscopes can determine the vehicle’s lateral and longitudinal stability characteristics. We can use it to assess the condition of the vehicle’s chassis. We also use stability in automobiles. For example, it determines if the car loses balance or is unstable while traveling on a curvy road.
5. Space stations:
MEMS gyroscopes and accelerometers help determine the space station’s orientation, speed, and direction.
How to choose an Accelerometer
Accelerometers help in motion capture systems, game controllers, and Kinect. They all can measure changes in motion. We do this by the accelerometer measuring the changes in acceleration caused by forces applied on a device.
Accelerometers can measure acceleration caused by gravity, which we can also use to detect gravity. The accelerometer can also measure static forces like downwards force or upwards force. But it cannot detect dynamic forces like movement and movement over time. So to find a good one, you need to consider the following:
1. Range:
Accelerometers can measure acceleration up to 5000 Gs. So if you want to measure accelerations with high precision, it is better to go with the accelerometer with a high range. They include an accelerometer with a range of 2 Gs or above.
2. Interface:
We can connect accelerometers through digital or analog. But to get the best performance, it is better to go with the accelerometer that uses a digital interface.
3. Sensitivity:
The sensitivity of an accelerometer is the amount of vertical force it can measure per the change in acceleration. Unfortunately, it is also associated with low sensitivity. So you will not measure it accurately if you are accelerating at a constant rate.
4. Axes:
There are two types of accelerometers, namely two or three axes.
The most common type of accelerometer that is in use today is the one that has only one axis. It looks like a mini 3-axis accelerometer. If you want to measure acceleration with high precision, you should go for the miniaturized 3-axis accelerometer. However, this type of accelerometer can be available on only a few devices. They are challenging to manufacture.
5. Power:
The mass of the device and the size of the circuit board will affect its performance sensitivity and power consumption. So before you go for any accelerometer, you must consider these factors.
6. Usage:
It is also essential to understand how to use the accelerometer in the device.
7. Cost:
Before deciding on an accelerometer to use in your project, you must also consider the cost. You should know that you can use Richter or tilt switches instead of accelerometers. This is when you want to measure acceleration on a small budget.
Types of Accelerometer
a. Grove – 3-Axis Digital Accelerometer ±16g Ultra-low Power (BMA400)
This is a product of the BMA400 sensor from Analog Devices. The Grove -3-Axis Accelerometer BMA400 is an ultra-low-powered digital accelerometer. We use it in robotics and medical devices.
b. ADXL 3-Axis Accelerometers series
There are three different series of accelerometers based on BMA200.
The ADXL3-03 is a low-power, high-performance 3-axis analog accelerometer. It is available in 1G and 4G options.
Most people believe the ADXL3 -05 is the most accurate class at ±5 µg. In addition, it provides increment and decrement detections. It has a resolution of ±2 µg per step throughout the full operating range.
How to choose a Gyroscope
Gyroscopes help in devices such as vehicles, cameras, and drones. We use them to help improve a device’s stability and measure speed.
Gyroscopes help reduce rollover accidents and provide more accurate speed readings.
You must choose your gyroscope wisely because not everyone has the same requirements. So there is no one size fits all gyroscope. This makes it even more difficult for you if you have no prior background knowledge about them.
These are the factors to consider when choosing a suitable gyroscope:
Range:
Gyroscopes can measure angular velocity up to 2000 degrees per second. So you need to choose one with a high range, such as a gyroscope with a range of 2000 degrees per second or above.
Range affects the amount of information you can get from the gyroscope. So you should choose one which has the highest range possible for your project.
Digital vs. Analog:
Digital gyroscopes are more expensive than analog ones. But they are easier to interface with and provide more accurate results. So to get good performance, you should choose an analog gyroscope over a digital one.
Conversion Ratio:
The conversion ratio of an analog gyroscope refers to the accuracy of the speed measured in degrees per second. An accurate speed measure is much preferable to an inaccurate one. So choose a gyroscope that has the highest possible conversion ratio. The parameters that govern the accuracy of a gyroscope are range, convert rate and temperature coefficient. So you will have to consider them when choosing one for your project.
Number of Axes:
Two gyroscopes are single and dual axes. A single-axis gyroscope is suitable for measuring angular velocity around a single axis. We can use it for applications such as stabilization. On the other hand, a dual-axis gyroscope is essential in navigation or flight control. So choosing a dual-axis one over the single-axis type is better.
Power:
Gyroscopes consume a lot of power. So you should choose a gyroscope with the lowest possible power consumption if you want to measure angular velocity but don’t have the money to go for a high-end gyroscope. Ten mW is much better than 0.5 mW.
Usage:
We use gyroscopes in many devices. They include drones, satellites, and flight control systems. Before choosing a gyroscope for your project, you must check the device’s requirements.
Cost:
You can save a lot of money by choosing an inexpensive gyroscope. It is not as important as other factors in selecting a good one.
Which Gyroscopes to buy
a. Grove – 6-Axis Accelerometer & Gyroscope:
The BMG160 is a 6-axis gyroscope and accelerometer in a single package. The LIS2MDL3-16000 is a low-power 6-axis accelerometer and gyroscope with 16 bit ADC resolution. It can sense angle rates with an upper limit of ±2,000°/sec
b. ADXL 3-Axis Gyroscopes
There are three different series of analog ADXL gyroscopes based on LS5016AL.
The ADXL3-12 is a low-power general-purpose high-performance 3-axis analog gyroscope. It has a full scale of ±200dps.
The ADXL3 -15 is the most accurate in its class at ±5 µg/DPS (roll) and ±2.5 µg/DPS (pitch and yaw). In addition, resolution remains consistent throughout the entire operating range.
The conversion ratio of the ADXL3-15 is much higher than the other models available in this series. This is why we have mentioned it.
c. DRV2605L 3-Axis Digital Gyroscope
The DRV2605L from Texas Instruments is a digital gyroscope. It uses MEMS sensor technology with an embedded MSP430 controller.
Applications compatible with this gyroscope include automotive, robotics, vision systems, and wearable computing.
The sensor has 3-axes, ±2g/±2g range, 0.01° resolution, and +/-0.1°/s bandwidth. It consumes a little less than one mA per axis, with 0.5V supply voltage.
Difference between Accelerometer and Gyroscope
When analyzing these two sensors, there are many similarities. You will find that they have similar capabilities and applications. So it is quite challenging to determine which one performs better.
This section will help you understand the differences between accelerometers and gyroscopes. Then, it will help you choose the right sensor for your project.
Function:
We use accelerometers to measure acceleration. On the other hand, a gyroscope can measure the angular rate and angular velocity. In short, accelerometers sense changes in speed and direction. Gyroscopes sense rotational speed.
Gyroscopes are also known as rate gyros or rotation sensors. However, this depends on their function.
It is famous for sensing Linear Acceleration, angle, and angular acceleration or rotation. Additionally, we can measure by combining an accelerometer and a gyroscope.
We refer to measuring the angle of rotation of a body using an accelerometer as angular rate sensing. The sensor measures changes in the tilt of a rotating body. This is what we call angular velocity when it senses movement. These movements are due to gravity, acceleration, and rotation. The three-axis accelerometer measures the change in tilt.
Sensing linear velocity is the measure of how fast the spinning body rotates. The gyroscope senses the angular velocity by measuring motion in the yaw axis (pitch and roll).
Gyroscopes measure the rotational speed in inertial navigation and flight control systems.
Robots also use gyroscopes as sensors to determine their orientation and maintain balance.
We can consider accelerometers as mini gyroscopes. This is because they do a similar angular rate measurement.
Signal to noise ratio:
The signal-to-noise ratio is the ratio between the signal level and the noise level observed by the detection device.
The higher the signal-to-noise ratio, the more sensitive it is to variations in the input.
The signal-to-noise ratio is essential when choosing a sensor. This is because it affects its accuracy and precision. For example, working with a sensor with a low SNR will not respond to small changes in output.
The gyroscope is a very sensitive sensor with high SNR to measure the smallest changes. As a result, accelerometer measurements are lower, defeating the purpose of an accelerometer.
We build Inertial Navigation Systems using gyroscopes. This is due to their sensitivity to angular velocity changes rather than accelerometers.
The gyroscope has an advantage over the accelerometer when dealing with drift. This is because of its constant measuring error.
Measurement of angular velocity:
Gyroscopes measure or sense the rotation of a rotating body. To get an accurate measurement, you must mount the gyroscope on a fixed point to control the direction of rotation.
The gyroscope is an electronic device. We use it to sense angular velocity and applied to 3D scanning, sensing, navigation, and position control systems.
Measuring linear velocity is insufficient for inertial guidance systems. This is because the space vehicle can move at high speeds and maintain orientation. However, we can use it in position control systems where the vehicle is stationary to get orientation information.
A gyroscope has several modes, such as horizontal, angular rate, and angular rate drift. Each type of mode is essential for different applications and conditions.
Horizontal Mode:
The basic mode measures rotational movement in an east or west direction, also called yaw. Yaw may also refer to it as pitch or roll, depending on which axis the gyroscope senses rotation in.
Conclusion
Finally, the right sensor to choose depends on the application and environmental conditions.
First, we need to determine what output is more important in the given application.
If it is possible to get raw data from the sensor, you should get an accelerometer over a gyroscope.
You should choose a gyroscope over an accelerometer if you need high accuracy and precision.
