Hall Effect Sensors and its Functional Area.

Hall Effect Sensors.

This effect was discovered by E.R. Hall in 1879 and is called the Hall effect. Hall effect sensors are the device which is activated by an external magnitude field. When the magnetic flux density around the sensor exceeds a certain pre- threshold, the sensor detects it and generate an output voltage called the Hall Voltage.

We know that a magnetic field has two important characteristics flux density and polarity. The output signal from a Hall effect sensors is the function of the magnetic field density around the device. When a beam of charged particle passes through a magnetic field, forces act on the particle and the beam deflected from its straight line path. A current flowing through a conductor is like a beam of moving charges and thus can be deflected by a magnetic field.

Working Principle

Hall Effect Sensors consists of a thin piece of rectangular p-type semiconductor material such as GaAs, indium arsenide passing a continuous current through itself. When the device is placed within a magnetic field, the magnetic flux line exerts a force on the semiconductor material which deflects the charges carries, electrons and holes, to either side of the semiconductor slab. As these electron and holes move sideward a potential difference is produced between the two sides of the semiconductor material by the build-up of these charges carries. Then the movement of the electron through the semiconductor materials affected by the presence of an external magnetic field which is at the right angle to it and this effect is greater in a flat rectangular shaped material. The Hall effect provides information regarding the types of magnetic poles and the magnitude of the magnetic field. Hall effect sensors are available with either linear or digital outputs. The output signal for linear sensors is taken directly from the output of the operational amplifiers with the output voltage being directly proportional to the magnetic field passing through the Hall sensors.

Applications

Hall Effects sensor is activated by a magnetic field and in many application, the device can be operated by a single permanent magnet attached to a moving device. There are many different types of magnet movement such as Head on, sideways, push-pull etc sensing movements.

1. The Hall effect sensors are immune to environmental contaminants and can be used under severe service conditions. Such a sensor can be used as position, displacement and proximity sensor if the object being sensed is fitted with a small permanent magnet. Can be used to determine the level of fuel in an automobile fuel tank. A magnet is attached to a float and as the level of fuel changes so that float distance from the Hall sensor changes. The results are a Hall Voltage output which is a measure of the distance of the float from the sensor and hence the level of the fuel in tank determined.
2. Another application of hall effect sensors is in the brushless D.C. Motors. With such motors, it is necessary to determine when the permanent magnet rotor is correctly aligned with the winding on the stators so that the current through the winding can be switched on at the right instant to maintain the rotor rotation.

Ideal Behavior of a Sensor/Transducer.

Ideal Behavior of a Sensor/Transducer.

Mechatronics design engineer must be knowing the capabilities and shortcomings of a transducer or measurements system to properly assess it's performance. There are a number of performance-related parameters of a transducer or measurement system. Sensor specifications inform the engineer and the user about the deviation from the ideal behaviour of the sensor.

The following terms are used to define the performance of the transducer and often measurement System as a whole. The design process begins with a need form, perhaps a customer or clients. This may be identified by market research Being used to establish the need for potential customers.

Range

The range of a transducer define the limits between which the input can vary. The span is the maximum value of the input minus the minimum value.

Error

The error is the difference between the results of the measurements and the true value of the quantity being measured. For example, if the measurements system gives a temperature reading of 45^0 C when the actual temperature is 42^0 C then the error is +3^0C.

Accuracy

Accuracy is the extent to which the value indicated by a measurements system might be wrong. It is thus the summation of all the possible error that is likely to occur as well as the accuracy to which the transducer has been calibrated.

Sensitivity

The sensitivity is the relationship indicating how much output here is per unit input. There can be the sensitivity of the transducer to temperature changes in the environment or perhaps fluctuations in the main voltage supply.

Hysteresis

The transducer can give different output from the same value of the quantity being measured according to whether that value has been reached by the continuous increasing change or a continuously decreasing change.

Stability

The stability of the transducer is its ability to give the same output when when used to measure a constant input over a period of time. The term drift is often used to describe the change in output that occurs over time. Zero drift is used for the change that occurs in output when there is zero input.

Dead band/Time

The dead band or dead space of a transducer is the range of input values for which there is no output. The dead time is the length of time from the application of an input until the output begins to respond and change.

Resolution

When the input varies continuously over the range, the output signal for some sensor may change in small steps. Example potentiometer. The resolution is the smallest change in the input values that will produce a considerable change in the output.

Non-linearity error

For many transducers, the linearity relationship between the input and output is assumed over the working range. in some transducer, however, have a truly linear relationship and thus the error occurs as a result of the assumption of linearity. This error is defined as the maximum difference from the straight line. various methods are used for the numerical expression of the non-linearity error. The difference occurs in determining the straight line relationship against which the error is specified.

Repeatability

The term repeatability of the transducer is used to describe it's ability to give the same output for repeated application of the describe the same input values. The error resulting from the same output not being given with repeated applications is usually expressed as a % of the full range output.

Types of Light Sensor and its Application.

Light Sensor

light sensors are semiconductors device and this is operation is based on the change in the resistance and current flow in the circuit when the light falls on them. 

there are three type of light sensor:-

1. Photodiode
2. Phototransistor
3. Photoresistor

 photodiode is semiconductor junction diodes which are connected into a circuit in reverse bias, so giving a very high resistance. With no incident light, the reverse current is almost negligible and is termed the dark current.when the light fall on the junction, extra hole electrons pair are produced and there is an increase in the reverse current and the diode resistance drops.

The photodiode is two terminal electronic devices which when exposed to light the current start flowing in the diode. It is operated in reverse bias. Basically, it converts light energy into electrical energy.

Working

The junction of the diode is. Illuminated by the light source, the photons strike the junction surface. The photons impart their energy in the form of light to the junction. Due to which electrons from valence band get the energy to jump into the conduction band and contribute to the current. The reverse current is very nearly proportional to the intensity of the light. For example, the current in the absence of light with a reverse bias of 3 volts might be 25uA and when illuminated by 25000 lumens /m^2 the current rises to 375 uA . The resistance of the device with no light is  120k ohm and with light is 8k ohm. A photodiode can thus be used as a variable resistance device controlled by the light incident on it. Photodiode has the very high response to the light.

Application

• photodiodes are condensed as one of the significant optoelectronics devices which is extensively used in the optical fibre communication system.
• it is used in the character recognition technique and IR remote control circuits.

Phototransistor

The phototransistors have light-sensitive collector base p-n junction. When there is no incident light there is a very small collector to emitter current. When light is incident, a base current is produced that is directly proportional to the light intensity. this leads to the production of a collector current which is then a measure of the light intensity.

Working

The two arrow point towards phototransistor indicate that the phototransistors are triggered by the light rays incident on it .the output of the phototransistors is taken from the emitter terminal and the light rays are allowed to enter the base region. the magnitude of the photocurrent generated by the phototransistors depends on the light intensity of the light falling on the transistor.

Application

• Counting system
• Encoder sensing
• Object detection
• Printer and optical control remote
• Light detectors.

Photoresistor

A photoresistor has a resistance which depends on the intensity of the light which is falling on it.decreases linearly as the intensity increases. The cadmium sulphide photoresistor is the most responsive to light having the wavelength shorter than about 515 nm and the cadmium selenide photoresistor for wavelength less than about 700nm.

Working

When the light falls on the photoresistor, some of the valence electron, which absorbs energy from the light and breaks the bonding with the atoms. the valence electron which breaks the binding with the atom is called the free electron. Because when the light energy falls on it, material get heated up and the electrons movement gradually increases, again if the energy increase then the electrons comes out from its threshold boundaries.

Application

• Streetlight
• Alarm device
• Street solar lamp
• Clock radios.

Evolution of Mechatronics in the Modern Technology.

Evolution of Mechatronics

The term Mechatronics was invented by a Japanese engineer in 1969, as a combination of 'mecha' from the mechanism and 'Tronics' from electronics. now the word has a wider meaning, being used to describe a philosophy in engineering technology in which there is coordinated and concurrently developed, integration of mechanical engineering with electronics and intelligent computer control in the design and manufacture of product and processes. as a result mechatronics products have many mechanical functions replaced with electronic ones. This result in much greater flexibility, easy redesign and reprogramming and the ability to carry out automated data collection.

Definitions

A formal definition of mechatronics is "The synergistic integration of mechanics and mechanical engineering, electronics, computer technology and IT to produce or enhance the products and system".

Mechatronics is the synergistic integration of sensors, actuators, signal conditioning, power electronics, decision and control algorithm, and computer hardware and software to manage the complexity, uncertainty and communication in the engineering system. According to the Mechatronics forum, a precise and common definition is as follows."Mechatronics is the synergistic integration of mechanical engineering with electronics and intelligent control algorithm in the design and manufacture of products processes".products and processes requiring inputs from more than one discipline can be realized through the integration. multidisciplinary is an additive process of bringing multiple disciplines together to bear on a problem.

In recent years, the application of digital microelectronics and computer in design and manufacturing sector has considerably improved productivity and quality of many mechanical products. automation and control method, adopting integrated embedded technology has become relevant to industries, machinery and consumer products. Mechatronics, an enabling discipline has already emerged to cater to the need for sophistication and flexibility and in fact has become a preferred choice for the current generation of the real-time automation and control solution for the traditional mechanical system.

A mechatronics system is no just a marriage of electrical and mechanical system and is more than just a control system; it is a complete integration of all of them in which there is the concurrent approach to the design. In the design of a car, robot, machine tool, washing machine cameras and many other machines. The technological design has become a high-risk endeavour due to the lack of knowledge and experience on interdisciplinary subject and methods. the advanced technological design is highly complex and interdisciplinary nature involving the synergistic integration of mechatronics, photonics, computronics and communication. Technological development and innovation would thus require simultaneous knowledge of discrete fundamentals.

Mechatronics, although still a relatively new term compared with many of the traditional branches of engineering, now appears firmly established. individuals industries and universities around the world are now using the term freely. At the research and development level. 

Technical areas are classified under the mechatronics discipline are;

1. Manufacturing
2. robotics
3. Automobiles
4. Actuation and sensor
5. Modelling and design
6. intelligent control
7. motion control
8. Vibration and noise control
9. System integration
10. Optical electronics

Examples of mechatronic systems

Consider the modern autofocus, auto exposure camera. to use the camera all you need to do is point it the subject and press the button to take the picture. The camera can automatically adjust the focus so that the subject is in focus and automatically adjust the aperture and shutter speed so that the correct exposure is given. you do not need to have to manually adjust focusing and aperture or shutter speed controls.

Job opportunities

Automobiles companies

Aerospace companies 

Madox Technology Pvt.Ltd.

Mechatronics Elevator

Systemantics India Pvt.Ltd.

Mechatronics Fze.

Petra mechatronics Middle East Trading LLC

Emirates Mechatronics Engineering Solution.

Salaries

In India: 35k to 45k pm initially

In Abroad: $70,000 to $85,000 annually.

Also Read Mechanical Actuating System Used in Mechatronics.

                          Functions of Microprocessor and applications.

Functions of Microprocessor and applications.

Introduction

It is an integrated circuit designed for use as a central processing unit of a computer. The CPU is the primary and central player in communication with the devices such as memory, input and output. The terms Microprocessor came into existence in the year 1971, when the Intel Corporation of America developed the first microprocessor Intel-4004 it was able to process just 4 bits. 

It is the digital device of the processor system which processes the data, fetching the instruction from memory, decoding and executing them. The microprocessor system that we are concerned are used as a control system and it called as embedded microprocessors. It performs certain arithmetic and logical operations to accept data from the input device and send results to the output. it is incorporated the functions of a CPU on a single integrated circuit or few integrated circuits.
The microprocessor system is consist of 

1. Central processing unit.
2. input-output interfaces.
3. Memory unit

Buses: Basically it is a communication link between the processing unit and the peripheral devices.

 1.Data Bus: it is used to transport a word to or from the CPU  and the memory or the output /input interfaces Each wire in the bus carries a binary signal 0 or 1. 

 2.Address Bus: It carries signals which indicate where data is to be found and so the selection of the certain memory location or input or output ports. Each storage location within a memory device has a unique identification.

3.Control Bus: The signals relating to control activities are carried by the control bus. it is necessary for the microprocessor to inform memory devices whether they are to read data from an input device or write data to an output device.

The constituent part of a microprocessor.

1. Arithmetic and logic unit(ALU): This unit is responsible for performing the data manipulation and other logical operation on the data.
2. Register: Internal data that the CPU is currently using is temporarily held in a group of registers while instructions are being executed. these are memory location within the microprocessor and are used to store the information.
3. Control unit: The control unit performs the most important function in the computer. it controls all other units and also controls the flow of data from one unit to another for performing computations.it generates the timing signals used to fetch a program instruction from memory and execute it. operations involving the microprocessor are reckoned in terms of the number of cycles they take.
4. Memory Unit: The memory unit in a microprocessor system stores binary data and takes the form of one or more integrated circuits. the data can be program instruction codes or number being operated on. this usually consists of chips of both ROMs and RAMs 
5. Output unit: After processing of the data in the arithmetic and logical unit, the results are displayed to the output world through this unit. the term peripheral devices are used for pieces of equipment that exchange data with a microprocessor system. for the microprocessor to input valid data from an input device, it needs to be certain that the interface chip has correctly latched the input data. it can do this by polling or an interrupt. 

Advantages of a microprocessor

1. Low cost
2. less heat generation 
3. low power consumption
4. high speed 
5. Small size
6. Reliable
7. Versatile
8. Portable

Also read  Requirement of An Ideal Control System.