Accelerometers in smartphones are quite frankly the amazing device created in this modern world. Nowadays there are so many features of smartphones that we don’t even know about while buying one. The new features are getting better and better that nobody likes to stay away from their phone these days, I’d be lost without mine. And one of the most common features of a smartphone is the auto-rotating screen. You would have probably used this feature while watching videos or maybe while playing Temple run. While watching a video on a device with this feature, the screen rotates as the orientation of the device is changed from portrait to landscape and vice versa. The interesting thing is that they know how they are being moved around and which way they are pointing. But How does a smartphone sense the change in orientation? Have you ever imagined that? Well, that’s all down to a tiny electromechanical device known as an accelerometer, a small device made up of axis-based motion sensing.
An accelerometer measures the acceleration force: the rate of change of velocity. Such forces may be static or dynamic. As anything on the surface of earth experiences a gravitational force, an accelerometer at rest on the surface of the earth (i.e. in case of static force) experiences the gravitational force of 9.8 m/s2 and the same accelerometer in free fall will experience zero force.
And in the case of dynamic force, it experiences both the gravitational force and the inertial force due to motion. So, By using the effect of gravitational force and inertial force, it measures orientation, movement, and vibration.
Application of Accelerometer
The accelerometer has the capacity to sense the motion from a micro-scale to a large scale. We all know the auto-rotate feature of smartphones and tablets, which happens due to accelerometer applications. Nowadays, accelerometers sensors are used not only in smartphones and tablets but also in other devices like navigation and flight control mechanisms in aircraft, in automobile industries to detect car crashes to deploy airbags almost instantaneously.
An accelerometer is used for safety purposes in laptops for keeping the hard discs safe, If the laptop were to suddenly drop while in use, the accelerometer would detect the sudden free fall and immediately turn off the hard drive to avoid the collision between the reading heads into the hard drive platter.
The mechanism used to determine the magnitude of earthquakes in the Seismometer is quite similar to the accelerometer where a pen with heavy mass is attached to the frame with the help of a spring. And when the earth shakes the frame shakes with it, but the pen attached with the spring takes time to move (due to the inertia of the heavy mass) resulting in the zigzag motion of the pen being traced on the paper.
How do they work?
An accelerometer works on Newton’s second law of motion, which states that the acceleration of an object is directly related to the net force and inversely related to its mass (i.e a=F/m). In other words, acceleration is the amount of force we need to move each unit of mass.
Accelerometer I think we all are familiar with this law of motion while traveling in a bus, car, or any vehicle. So when we are sitting on the seat of the bus, while accelerating we will experience ourselves thumping back to the seat (due to the inertia of our body mass). The more the bus accelerates the more force will push us back. Now imagine ourselves as free mass and the bus to be a frame. When the frame moves forward then the mass will experience the backward force. So, the accelerometer works in the same way whose structure consists of a mass attached to the frame such that the mass is free to move inside the frame. When the accelerometer moves, the mass will experience a backward force. And this backward force experienced by the mass inside the frame is used differently in other accelerometers.
3 important types of accelerometers
Capacitive or MEMS(Micro Electro-Mechanical-System) Accelerometer:
The MEMS is the advanced form of the capacitive accelerometer. This type of accelerometer is the most commonly used accelerometer in smartphones, tablets, and other electronic devices because of its size and affordability. the accelerometer is responsible for “flipping” the screen when the device is rotated.
Piezo-electric Accelerometer:
In this type, the sensors are made of crystals or ceramics like lead zirconate, lead titanate, etc. This sensor absorbs the vibrations and produces the respective amount of electrical signals using the principle of the Piezoelectric effect.
Piezo-resistive Accelerometer:
It measures the vibrations with respect to the amount of resistance produced using the principle of the Piezo-resistive effect. It is responsive and efficient while measuring very little vibrations as it uses dc current.
Here is what happens if we turn our phone sideways:
In the above images, the working of the auto-rotate screen feature in a smartphone is shown using simple mechanisms of the accelerometer (placing the individual accelerometer on all axis). When in portrait mode an accelerometer in the x-axis will experience the gravitational force, accelerometer “A” in the above image, and when we turn to landscape mode another accelerometer “B” will experience the gravitational force. That force is used in different types of the accelerometer to determine the orientation of the phone when it senses that that phone is
tilted sideways then the accelerometer will send the signal to the controller chip in the phone to rotate the screen.
tilted sideways then the accelerometer will send the signal to the controller chip in the phone to rotate the screen.
Tags:
Electronics