Railway tracking System

      Research on Rail Safety Security System
This paper analysis of  the integrated use of safety monitoring with the domestic and international latest research on rail safety protection system, and focus on the implementation of an organic whole system, with the monitoring and early warning, risk assessment, predictive control and emergency rescue system. The system framework, contents and system structure of Security system is proposed completely. It’s pointed out that the Security system is a negative feedback system composed of by safety monitoring and warning system, risk assessment and emergency rescue system. Safety monitoring and warning system focus on the monitoring target monitoring, early warning, tracking, integration of decision-making, for objective and subjective risks factors. Risk assessment system analysis the occurrence of a major Security risk mechanism, determines the standard of the future short, medium and long term safety conditions, and give prop for development of safety indicators, accident analysis and safety standards. Emergency rescue system is with the goal of rapid and effective rescue work for accident, to minimize casualties and property losses.
Along with the transportation develops towards high-speed, high-density, over loading, technique concentrated, complex of the technique systemic constitute, and the high linkage between business system, the safety Security work will face exceptional severe challenge. The objects related to safety Security consist of natural disasters, foundation devices and emergencies. Any local damage and un-control may evolve to a global damage and un-control during the subway is in motion and do business. However, now the question of safety Security system is that the apply and analysis on information of safety monitoring is on start-up period, the whole benefit of prediction control and emergency rescue by monitor data has not yet been fully developed, the primary cause of the problem is lack of systemic rail transportation Security and technology criterion which is adaptive to the system and possess the industry characteristic. Following the development of the system on safety monitoring and early warming, it will accumulate a mass of Security monitoring data. If the data is effectively fusion, storage, and synthetically applied, the Co-relational research on rail transportation safety Security system is becoming highly valued step by step in recent years. Research on the theory and technology of rail transportation safety Security has bear fruit according to the literatures. Literature [1] described the depart control of rail transportation operating system and presented the optimal strategy and realize of depart intelligent decision support system based on Petri net. Literature [2] formally modeled definition, design and realization of the self-check function in automatic driving control software. Literature [3] had researched the analysis and design of the train strategic decision supporting system by using the method facing objects. Literature [4] optimized the train’s initiative driving by using linear quadratic Gaussian (LQG) method and hereditary algorithm. Literature [5] presented and brought out the distributed strategy decision supporting system of the train station and train control along the line. Literature [6] researched the optimized operation of the train based on the neural networks. All of these achievements paved the path to build and improve the rail intelligent train control system and rail transportation scourges prevention facing the safety Security. It also invested abundant of labour power and financial resources to keep away and control the scourges, thereby the whole scourge early warning and monitor political system is formed. The system of scourge early warming used scientific early warming methods, gathered every kind of external data leading to scourge, advanced early warming to scourges such as flooded line and collapsed line, carried out responding scourge warming, formulated travelling regulation under scourges, which prevented the accidents of scourge and Security transportation safety. Scourge monitoring system directly monitored the scourges which are difficultly predicted, such as rolling stones, collapse, broken bridges, which ensured the running train can stop in time and transferred the information to any departments. The system frame of American rail traffic intelligent transportation system, which named IRS, contained system frame of proactive train controlling system, which can be used to control train safety, reliable, punctual, effective operating, and by avoiding train colliding, decreasing the negligence of rail road workers, reducing facilities broken and over speed accidents. The standard current situation of international standardization institution and each country safety Security system concerning is:
UTC (Union International des Chemise defers, International Union of railways), UTC is the biggest international standardization institution of the world rail transportation. This organization is a non-government international rail transportation institute, which is subject of European rail transportation, and China is one member country in it. A set of standardizations related to safety Security system quickly developed for it. (2) ISO, ISO related to the rail transportation standard is the 45 item-rail transportation projects. Although now the part of ISO rail transportation is emphasized on project material, but these standards are closely interrelated to transportation safety. (3) IEEE (Institute of Electrical and Electronics Engineers), IEEE standardization committee is responsible for the survey, impel, management of IEEE standard, pondering and proposing IEEE standard. For the past few years, IEEE standardization committee is very active in standardization research part of rail transportation information and control, closely follow after releasing many standards in this region, and some parts is related to transportation safety [7]. (4) ERRI (ERRI European Rail Research Institute)ERRI is under the lead of UIC and it is a rail technical research institute which gathers rail traffic engineers in every country. Meanwhile, along with the typical RITS system-ERTMS continually deepens, ERRI plays a decisive role in the forming of the world rail traffic standard. (5) JIS, section E in JIS standard object is directly related to rail transportation, including line general standard, locomotive signal, signal servicing installation, rail traffic vehicle general standard , high-speed train , passenger and freight vehicle, tight wire railway standard. JIS present standardization strategy of the same.
 Rail traffic safety system is composed of three parts: the safety monitoring and early warning system, risk assessment system and emergency rescue system. Emergency rescue system is centre, safety monitoring and early warning and risk assessment system is the means. In this system, safety monitoring warning system is controller and transportation safety factors is the object; the input is a closed-loop system of emergency rescue level. Among them, safety factors are generalized concepts, including not only individual subjective and objective factors which lead to the danger, but also the relationship between factors and combination Safety monitoring and early warning system Rail traffic safety monitoring and early warning system is aiming at subjective and hidden danger factors. Monitoring network is composed by monitoring stations, and observing monitoring target, tracking, early warning, recognizing, monitoring and reporting the development state. The monitoring content is composed of operation action of person in key position, the running condition of vehicle, the vehicle loading condition and infrastructure condition; transportation safety synthetically monitoring information base is formed by information fusion, providing timely information to prevention, predicting of hidden danger and emergency rescue. Safety monitoring and early warning system uses distributed network monitoring stations to monitor, track the safety station of targets. The key technology of rail traffic safety monitoring and early warning system is system interface. System interface contains not only integration technology of site safety monitoring system, but also information exchange technology of safety subsystems interconnection or integration. The contents include the classification of the interface, form of structure and realization. According to the technical content and layer of structure, system interface is divided into: system interface and monitoring level interface. System interface: system interface refers to the safety monitoring system and the interface of each safety subsystem. System interface integrates and plans subsystem information base on the aspects of system interconnection, part function, characteristic and structure, builds uniform standard information storage structure, organization structure, circulation mechanism, Monitoring level interface: monitoring level is that safety subsystem interface processes the data collection and forms standardized interface. Monitoring level interface is related to their own function features of safety device. ii. Early warning decision-making of monitoring network the same major safety monitoring system in monitoring network which deployed at the site is independence. Because of the monitoring results are influenced by many random factors, the single point estimation judgement may not be necessarily accurate in monitoring and warning, which means false alarm and leakage alarm(false alarm is that target under monitoring system is out of action, but it actual trouble-free. False alarm rate is in a period, the number of fault alarm displaying contrast to the total alarm displaying). Therefore, the result of judgement will objective, when the monitoring network stations increase a participant of fusion judgement node, judge monitoring system become integrated, the participants with the determination results objectively.
The monitoring network system containing several stations and a decision fusion monitoring network system can be divided into two kinds of structure ,a kind of monitoring and early warning decision-making model which composes by many stations and a fusion centre, called MDOF model.

CONCLUSION:

The paper based on analysing and summarizing co-relational research results of rail traffic safety Security, and it presents systematically the traffic safety Security system which should be served as a unity including safety monitoring and early warning system, risk evaluation system and emergency rescuing system. It realizes information fusion, information sharing and technical standardization. In the paper, rail traffic safety management system and Security management system is proposed and founded to adapt to the new features nowadays. After minutely stating the detailed technical frame design of safety monitoring and early warning system, risk evaluation system and emergency rescuing system, the paper integrally presents the system frame, research contents and system constitute of safety Security system. Synthetic safety Security system can develop synthetically monitoring, forecasting, early warning, disaster prevention and rescuing strategy service function, make that it can cohere with the work of some department, such as safety operating, infrastructure maintenance, quick emergency, and give full play to the function of Security safety devices and safety monitoring system.

CURRENT SENSOR

High-wattage appliances like electric irons, ovens and heaters result in unnecessary power loss if left ‘on’ for hours unnoticed. Here is a circuit that senses the flow of current through the appliances and gives audible beeps every fifteen minutes to remind you of power-’on’ status. This is a non-contact version of current monitor and can sense the flow of current in high-current appliances from a distance of up to 30 cm .It uses transistors in the input to provide very a standard step-down transformer (0- 9V, 500mA) as the current sensor. Its secondary winding is left open, while the primary winding ends are used to detect the current. The primary ends of the transformer are connected to a full-wave bridge rectifier comprising diodes D1 through D4. The rectified output is connected to the non-inverting input of IC CA3140 (IC1). IC CA3140 is a 4.5MHz BIMOS operational amplifier with MOSFET input and bipolar transistor output. It has gate-protected MOSFET (PMOS) transistors in the input to provide very high input impedance (1.5 T-ohms), very low input current (10 pA) and high-speed switching performance. The inverting input of IC1 is preset with VR1. In the standby mode, the primary of the transformer accepts e.m.f. from the instrument or surrounding atmosphere, which results in low-voltage input to IC1. This low voltage at the non-inverting input keeps the output of IC1 low. Thus transistor T1 doesn’t conduct and pin 12 of IC2 goes high to disable IC2. As a result, the remaining part of the cir gets inactivated. When a high-current appliance is switched on, there will be a current drain in the primary of the transformer to the negative rail due to an increase in the e.m.f. caused by the flow of current through the appliance. This results in voltage rise at the non-inverting input and the output of IC1 becomes high. This high output drives transistor T1 into conduction and the reset pin of IC2 becomes low, which enables IC2. IC CD4060 (IC2) is a 14-stage ripple counter. It is used as a 15-minute timer by feeding Q9 output to the piezo buzzer for aural alarm through the intermediate circuitry. Resistors R5 and R6 along with capacitor C1 maintain the oscillations in IC2 as indicated by blinking LED1. The high output from IC2 is used to activate a simple oscillator comprising transistors T2 and T3, resistors R8 and R10, and capacitor C2. When the Q9 output of IC2 becomes high, zener diode ZD1 provides 3.1 volts to the base of transitor T2. Since transistor T2 is biased by a high value resistor (R8), it will not conduct immediately. Capacitor C2 slowly charges and when the voltage at the base of T2 increases above 0.6 volt, it conducts. When T2 conducts, the base of T3 turns low and it also conducts. The piezo buzzer connected to the collector of T3 gives a short beep as capacitor C2 discharges. This sequence of IC2 output at Q9 becoming high and conduction of transistors T2 and T3 resulting in beep sound repeats at short intervals.

REMOTE OPERATED DOMESTIC APPLIANCES CONTROL BY ANDROID APPLICATION

The project is designed to operate electrical loads using an Android application device.  The system operates electrical loads depending on the data transmitted from the Android application device. Operating conventional wall switches is difficult for elderly or physically handicapped people. This proposed system solves the problem by integrating house hold appliances to a control unit that can be operated by an Android smart-phone/Tablet etc.
Remote operation is achieved by any smart-phone/Tablet etc., with Android OS, upon a GUI (Graphical User Interface) based touch screen operation, interfaced to the microcontroller of 8051 family. The program on the microcontroller serially communicates with Bluetooth device to generate respective output based on the input data (sent from Android application device) to operate a set of relays through a relay driver IC. The loads are interfaced to the control unit through the relays. The system can be used in existing domestic area for either operating the loads through conventional switches.
The power supply consists of a step down transformer 230/12V, which steps down the voltage to 12V AC. This is converted to DC using a Bridge rectifier. The ripples are removed using a capacitive filter and it is then regulated to +5V using a voltage regulator 7805 which is required for the operation of the microcontroller and other components.

RF BASED HOME AUTOMATION SYSTEM

The main objective of this project is to develop a home automation system with a RF controlled remote. As technology is advancing so houses are also getting smarter. Modern houses are gradually shifting from conventional switches to centralized control system, involving RF controlled switches. Presently, conventional wall switches located in different parts of the house makes it difficult for the user to go near them to operate. Even more it becomes more difficult for the elderly or physically handicapped people to do so. Remote controlled home automation system provides a simpler solution with RF technology.

In order to achieve this, a RF remote is interfaced to the microcontroller on transmitter side which sends ON/OFF commands to the receiver where loads are connected. By operating the specified remote switch on the transmitter, the loads can be turned ON/OFF remotely through wireless technology. The microcontroller used here is of 8051 family. The loads are interfaced to the microcontroller using opto-isolators and triacs.

RAILWAY TRACK SECURITY SYSTEM

The main problem is about railway track crack detection at the earliest to avoid accidents. Therefore it is essential that such problems must be communicated immediately to the concerned authorities by using GSM technology for appropriate action.
This project uses a microcontroller from 8051 family. The primary objective of this project is to detect the crack in the railway track and alert the nearby station through effective and highly reliable communication mode. To demonstrate this project, two rails forming the part of the track are made using a pair of wire which is wired with a detachable jumper in between each wire/track. Removing the detachable jumper creates a fault in the respective track; otherwise it is generally shorted by the jumper wire to simulate healthy track condition.
Removing the jumpers result in driving transistors delivering a different logic to the controller. The program thereafter takes over to send an SMS through GSM modem interfaced through MAX232 level shifter IC to the microcontroller. An LCD is also interfaced with the MC to display the status of GSM and track condition. Thus the proposed model is designed to recognize the cracks in the railway tracks and provides instant information to the concerned railway authorities. The power supply consists of a step down transformer 230/12V, which steps down the voltage to 12V AC. This is converted to DC using a Bridge rectifier. The ripples are removed using a capacitive filter and it is then regulated to +5V using a voltage regulator 7805 which is required 

Convert 1 to 5V signal to 4- to 20-mA output

Despite the long-predicted demise of the 4- to 20-mA current loop, this analog interface is still the most common method of connecting current-loop sources to a sensing circuit. This interface requires the conversion of a voltage signal—typically, 1 to 5V—to a 4- to 20-mA output. Stringent accuracy requirements dictate the use of either expensive precision resistors or a trimming potentiometer to calibrate out the initial error of less precise devices to meet the design goals.

Neither technique is optimal in today’s surface-mounted, automatic-test-equipment-driven production environment. It’s difficult to get precise resistors in surface-mount packages, and trim
ming potentiometers require human intervention, a requirement that is incompatible with production goals.
The Linear Technology LT5400 quad matched resistor network helps to solve these issues in a simple circuit that requires no trim adjustments but achieves a total error of less than 0.2% (Figure 1). The circuit uses two amplifier stages to exploit the unique matching characteristics of the LT5400. The first stage applies a 1 to 5V output—typically, from a DAC—to the non - inverting input of op amp IC1A. This voltage sets the current through R1 to exactly VIN/R1 through FET Q2. The same current is pulled down through R2, so the voltage at the bottom of R2 is the 24V loop supply minus the input voltage.
This portion of the circuit has three main error sources: the matching of R1 and R2, IC1A’s offset voltage, and Q2’s leakage. The exact values of R1 and R2 are not critical, but they must exactly match each other. The LT5400A grade achieves this goal with ±0.01% error. The LT1490A has less-than-700-μV offset voltage over 0 to 70°C. This voltage contributes 0.07% error at an input voltage of 1V. The NDS7002A has a leakage current of 10 NA, although it is usually much less. This leakage current represents an error of 0.001%.
The second stage holds the voltage on R3 equal to the voltage on R2 by pulling current through Q1. Because the voltage across R2 equals the input voltage, the current through Q1 is exactly the input voltage divided by R3. By using a precision 250Ω current shunt for R3, the current accurately tracks the input voltage.
The error sources for the second stage are R3’s value, IC1B’s offset voltage, and Q1’s leakage current. Resistor R3 directly sets the output current, so its value is crucial to the precision of the circuit. This circuit takes advantage of the commonly used 250Ω current-loop-completion shunt resistor. The Riedon SF-2 part in the figure has 0.1% initial accuracy and low temperature drift. As in the first stage, offset voltage contributes no more than 0.07% error. Q1 has less than 100-nA leakage, yielding a maximum error of 0.0025%.
Total output error is better than 0.2% without any trimming. Current-sensing resistor R3 is the dominant source of error. If you use a higher-quality device, such as the Vishay PLT series, you can achieve an accuracy of 0.1%. Current-loop outputs are subject to considerable stresses in use. Diodes D1 and D2 from the output to the 24V loop supply and ground help protect Q1; R6 provides some isolation. You can achieve more isolation by increasing the value of R6, with the trade-off of some compliance voltage at the output.
If the maximum output-voltage requirement is less than 10V, you can increase R6’s value to 100Ω, affording even more isolation from output stress. If your design requires increased protection, you can fit a transient-voltage suppressor to the output with some loss of accuracy due to leakage current.
This design uses only two of the four matched resistors in the LT5400 package. You can use the other two for other circuit functions, such as a precision inverter, or another 4- to 20-mA converter. Alternatively, you can place the other resistors in parallel with R1 and R2. This approach lowers the resistor’s statistical error contribution by the square root of two.

USB Booster..

As you probably know, the USB 2.0 ports can deliver up to 500 mA that means about 2.5W. But sometimes you might need more power to connect an external HDD or other peripherals and the USB ports just cannot deliver enough current. In this case you can buy USB hubs that have an external power adapter required to boost the power or you can build a simple or complex circuit that can do the same thing.  We are providing a very simple design involves the use of the 7805 voltage regulator that can deliver 5V and 1A.
The USB serial bus can be configured for connecting several peripheral devices to a single PC. It is more complex than RS232, but faster and simpler for PC expansion. Since a PC can supply only a limited power to the external devices connected through its USB port, when too many devices are connected simultaneously, there is a possibility of power shortage. Therefore an external power source has to be added to power the external devices. In USB, two different types of connectors are used: type A and type B. The circuit presented here is an addon unit, designed to add more power to a USB supply line (type-A). When power signal from the PC (+5V) is received through socket A, LED1 glows, opto- diac IC1 conducts and TRIAC1 is triggered, resulting in availability of mains supply from the primary of transformer X1. Now transformer X1 delivers 12V at its secondary, which is rectified by a bridge rectifier comprising diodes D1 through D4 and filtered by capacitor C2. Regulator 7805 is used to stabilize the rectified DC. Capacitor C3 at the output of the regulator bypasses the ripples present in the rectified DC output. LED1 indicates the status of the USB power booster circuit. Assemble the circuit on a general purpose PCB and enclose in a suitable cabinet. Bring out the +5V, ground and data points in the type-A socket. Connect the data cables as assigned in the circuit and the USB power booster is ready t o function.

Bioinformatics Applications

Machine Learning Methods in Bioinformatics Applications


The proteomics is an important domain where machine learning techniques are applied in bioinformatics. In the proteomics, two main applications of computational methods are protein structure prediction and protein function prediction. Generally, the first is an optimization problem and the second is a classification problem. Evolutionary algorithm (EA) based methods are the main optimization technologies for protein structure prediction, such as genetic algorithm (GA), estimation distribution algorithm (EDA), etc. Supervised and unsupervised classification methods are often used to predict protein function, such as Clustering, SVM, NN, etc.

SVM

 Support Vector Machines for Real-world Pattern Recognition

SVM is a nonlinear pattern recognition algorithm based on kernel methods. In contrast to linear methods, kernel methods map the original parameter vectors into a higher (possibly infinite) dimensional feature space through a nonlinear kernel function. Without need to compute the nonlinear mapping explicitly, dot-products can be computed efficiently in higher dimensional space. The dominant feature which makes SVM very attractive is that classes which are nonlinearly separable in the original space can be linearly separated in the higher dimensional feature space. Thus SVM is capable to solve complex nonlinear pattern recognition problems. Important characteristics of SVM are its ability to solve pattern recognition problems by means of convex quadratic programming (QP), and also the sparseness resulting from this QP problem.

Yin-Yang EAs Balancing Adaptivity and Diversity

Evolutionary algorithms (EAs) are search and optimization algorithms based on the principles of natural evolution, which have found successful applications in bio genetics, computer science, engineering, economics, chemistry, manufacturing, mathematics, physics and other fields.
   In applying EAs to solve large-scale real world problems, however, confronted with the conflict between accuracy and speed, EAs often result in an unsatisfactory compromise. Furthermore, one of the commonest difficulties encountered is premature convergence.

Quasi-ARX Modeling and Identification

Neural networks (NNs) and neurofuzzy networks (NFs) have been proved to have universal approximation ability. They can learn any non linear mapping. Many non linear ARMAX models have been proposed based directly on NNs and NFs. However, system identification is always followed by certain applications such as system control and fault diagnosis. From a user's point of view, NNs and NFs are not user-friendly since they do not have structures favourable to the applications of system control and fault diagnosis. To solve this problem, it is natural to consider a modelling scheme to construct models consisting of two parts: macro-part and kernel-part. The macro-part is a user-friendly interface constructed using application specific knowledge and the nature of network structure; efforts in this part are made to introduce some properties favourable to certain applications, while to embed the resulted model complexity in the coefficients. The kernel-part is a flexible multi-input multi-output (MIMO) non linear model such as NN and NF, etc. which is used to represent the complicated coefficients of macro-parts. Non linear models constructed in this way are expected to be user-friendly and to have excellent presentation ability.

A Hybrid Brain-Computer Interface for Smart Home Control

Hybrid Brain-Computer Interface :

Brain-computer interfaces (BCI) provide a new communication channel between the human brain and a computer without using any muscle activities. Applications of BCI systems comprise communication, restoration of movements or environmental control. Within this study we propose a combined P300 and steady-state visually evoked potential (SSVEP) based BCI system for controlling finally a smart home environment. Firstly a P300 based BCI system was developed and tested in a virtual smart home environment implementation to work with a high accuracy and a high degree of freedom. Secondly, in order to initiate and stop the operation of the P300 BCI a SSVEP based toggle switch was implemented. Results indicate that a P300 based system is very well suitable for applications with several controllable devices and where a discrete control command is desired. A SSVEP based system is more suitable if a continuous control signal is needed and the number of commands is rather limited. The combination of a SSVEP based BCI as a toggle switch to initiate and stop the P300 selection yielded in all subjects’ very high reliability and accuracy
SM4all – smart home control with BCI

Android projects for engineering students


 Top most android based project idea used with new technology 


1. DENSITY BASED AUTO TRAFFIC SIGNAL CONTROL WITH    ANDROID BASED REMOTE OVERRIDE
                                       
                                                ABSTRACT
The project is designed to develop a density based dynamic traffic signal system having remote override facilities. During normal time the signal timing changes automatically on sensing the traffic density at the junction but in the event of any emergency vehicle like ambulance, fire brigade etc. requiring priority are built in with Android application device remote control to override the set timing by providing instantaneous green signal in the desired direction while blocking the other lanes by red signal for some time.
Traffic congestion is a severe problem in many major cities across the world thus it is felt imperative to provide such facilities to important vehicles. Conventional traffic light system is based on fixed time concept allotted to each side of the junction which cannot be varied as per varying traffic density. Junction timings allotted are fixed. Sometimes higher traffic density at one side of the junction demands longer green time as compared to standard allotted time. The proposed system using a microcontroller of 8051 family duly interfaced with sensors, changes the junction timing automatically to accommodate movement of vehicles smoothly avoiding unnecessary waiting time at the junction. The sensors used in this project are IR and photodiodes are in line of sight configuration across the loads to detect the density at the traffic signal. The density of the vehicles is measured in three zones i.e., low, medium, high based on which timings are allotted accordingly. The override feature is activated by an on board Bluetooth device from the Android application device operated from the emergency vehicle. Remote operation is achieved by any smart-phone/Tablet etc., with Android OS, upon a GUI (Graphical User Interface) based touch screen operation. Further the project can be enhanced by synchronizing all the traffic junctions in the city by establishing a network among them. The network can be wired or wireless. This synchronization will greatly help in reducing traffic congestion.

  HARDWARE REQUIREMENTS:
      8051 series Microcontroller, LEDs, Voltage Regulator, Resistors,     Capacitors, Crystal, Diodes, Transformer, IR-LED & Photodiodes, Transistor,     Bluetooth device.

SOFTWARE REQUIREMENTS:
           Keil compiler


Convert 1 to 5V signal to 4- to 20-mA output

Despite the long-predicted demise of the 4- to 20-mA current loop, this analog interface is still the most common method of connecting current-loop sources to a sensing circuit. This interface requires the conversion of a voltage signal—typically, 1 to 5V—to a 4- to 20-mA output. Stringent accuracy requirements dictate the use of either expensive precision resistors or a trimming potentiometer to calibrate out the initial error of less precise devices to meet the design goals.
Neither technique is optimal in today’s surface-mounted, automatic-test-equipment-driven production environment. It’s difficult to get precise resistors in surface-mount packages, and trim
ming potentiometers require human intervention, a requirement that is incompatible with production goals.
The Linear Technology LT5400 quad matched resistor network helps to solve these issues in a simple circuit that requires no trim adjustments but achieves a total error of less than 0.2% (Figure 1). The circuit uses two amplifier stages to exploit the unique matching characteristics of the LT5400. The first stage applies a 1 to 5V output—typically, from a DAC—to the non - inverting input of op amp IC1A. This voltage sets the current through R1 to exactly VIN/R1 through FET Q2. The same current is pulled down through R2, so the voltage at the bottom of R2 is the 24V loop supply minus the input voltage.

Internal configuration of microcontroller

What is inside micro controller?



Obviously, everything that occurs in the micro controller occurs at high speed and quite simple, but it would not be so useful if there are no special interfaces which make it complete.
Program Memory (ROM)
The Program Memory is a type of memory which permanently stores a program being executed. Obviously, the maximal length of the program that can be written to depends on the size of the memory. Program memory can be built in the micro controller or added from outside as a separate chip, which depends on type of the micro controller. Both variants have advantages and disadvantages: if added from outside, the micro controller is cheaper and program can be considerably longer. At the same time, a number of available pins is decremented as the micro controller uses its own input/output ports to be connected to the memory. The capacity of Internal Program Memory is usually smaller and more expensive but such a chip has more possibilities of connecting to peripheral environment. Program memory size ranges from 512 B to 64 KB.
Data Memory (RAM)
Data Memory is a type of memory used for temporary storing and keeping different data and constants created and used during operating process. The content of this memory is erased once the power is off. For example: when the program performs addition, it is necessary to have a register presenting what in everyday life is called “a sum”. For that purpose one of the registers in RAM is named as such and serves for storing results of addition. Data memory size goes up to a few KB's.
EEPROM Memory


The EEPROM Memory is a special type of memory which not all the types of the micro controllers have. Its content can be changed during program execution (similar to RAM), but it is permanently saved even after the power goes off (similar to ROM). It is used for storing different values created and used during operating process and which must be saved upon turning off the device (calibration values, codes, values to count up to etc.). A disadvantage of this memory is that programming is relatively slow- measured in milliseconds.
SFRs (Special Function Registers)
SFRs are a particular part of memory whose purpose is defined in advance by the producer. Each of these registers have its name and control some of interfaces within the micro controller. For example: by writing zero or one to the SFR controlling some input/output port, each of the port pins can be configured as input or output (each bit in this register controls the purpose of one single pin).

Program Counter
Program Counter is an engine which starts the program and indicates the address in memory where next instruction to execute is found. Immediately after its execution, the value of the counter is incremented by 1. For this automatic increment, the program executes one instruction at a time as it is written. However…the program counter value could be changed at any moment, which will cause “jump” to a new location in the program memory. This is how subroutines or branch instructions are executed. When finding its new place in the program, the counter resumes even automatic counting +1, +1, +1…
CPU (Central Processor Unit)
As its name tells, this is "Big Brother" who monitors and controls all operations being performed within the micro controller and the user cannot affect its work. It consists of several smaller units. The most important are:
Instruction decoder - a part of electronics which recognizes program instructions and on the basis of which runs other circuits.
Arithmetical Logical Unit (ALU) - performs all mathematical and logical operations with data. The features of this circuit are described in the "instruction set" which differs for each type of the micro controller.
Accumulator - is a special type of the SFR closely related to operating mode of the ALU. It is a kind of desk on which all data needed to perform some operation on are set (addition, shift etc.). It also contains a result, ready to be used further in operation. One of the SFRs, called the Status Register, is closely related to the accumulator, showing at any time the "status" of a number being in the accumulator (the number is greater than or less than zero etc.).

Bit - a word invented to confuse people who start handling electronics. In practice (only in practice) this word indicates whether the voltage is applied to an electrical conductor or not. In the first case, a logical one is present on the pin, i.e. the bit’s value is 1. Otherwise, if the voltage level is 0 V, i.e. a logical zero is present on the pin, the bit’s value is 0. It is more complicated in theory where the bit is actually a digit in a binary system, whereas, a bit is just a bit whose value amounts 0 or 1 (in decade system we are used to the digits’ value amounting 0, 1 , 2 , 3 , …..8 or 9).
Input/output ports (I/O Ports):
The micro controller cannot be of any use without being connected to peripheral devices. For that reason each micro controller has one or more registers connected to its pins (called ports in this case).
The oscillator can be compared with rhythm section of a mini orchestra. Equalized pulses coming from this circuit enable harmonious and synchronise operating of all other parts of the micro controller. It is commonly configured so as to use quartz-crystal or ceramics resonator for frequency stabilization. Besides, it can often operate without elements for frequency stabilization (like RC oscillator). It is important to know that instructions are not executed at the rate ordered by oscillator but several times slower. The reason for this is that each instruction is executed in several steps (In some micro controllers execution time of all instructions is equal, while in others micro controllers execution time differs for different instructions). Consequently, if your system uses quartz-crystal of 20 MHz, execution time of a program instruction is not 50 nS but 200, 400 or even 800 nS!
Timers/Counters
Most programs use in some way these miniature electronic "stopwatches". They are mostly 8- or 16-bit SFRs whose value is automatically incremented with each coming pulse. Once the register is completely "filled up"- an interrupt is generated !
If the registers use internal oscillator for its operating then it is possible to measure the time between two events ( if the register value is T1 at the moment measuring has started, and T2 at the moment measuring has finished, then the time that has passed is equal to the value gained by their subtraction T2-T1 ). If the registers for its operating use pulses coming from external source then such a timer is converted to counter.
This is a very simple explanation used to describe the essence of the operating. It’s a bit more complicated in practice.

Introduction to Embedded System


An Embedded system can be defined as a computer system designed to perform the specific functions.
A specialized computer system that is part of a larger system or machine. Typically, an embedded system is housed on a single microprocessor board with the programs stored in ROM. Virtually all appliances that have a digital interface -watches, microwaves, VCR's, cars -- utilize embedded systems. Some embedded systems include an operating system, but many are so specialized that the entire logic can be implemented as a single program.This generally goes with real-time computing constraints.
Architecture and Programming of 8051 Micro controllers :
Learn in a very quick and easy way to program 8051 micro controller using many practical examples we have provided for you. Despite its relative old age, 8051 is still the most commonly used micro controller at present. The blog contains details of its architecture and many practical examples, both simple and complex, useful program routines, instructions on handling the programmer for Atmel 51 series, and the guide on using the development systems for Atmel micro controllers. 
Introduction :
It was electricity in the beginning....The people were happy because they did not know that it was existing all around them and that it could be utilized. It was fine. And then Faraday came and the stone has started rolling slowly...
During the time, the first machines using a new sort of energy appeared accompanied with people who knew something about electricity. A long time has passed since then and just when civilization got used to this innovation and stopped paying attention to what a new generation of specialists were doing, someone came up with an idea that electrons could be a very convenient toy being closed in a glass pipe. At first sight, it was only a good idea, but there was no return, electronics was born and the stone continued rolling down the hill faster and faster...
A new science - new specialists. The blue coats were replaced with white ones and people who knew something about electronics appeared on stage. While the rest of the humanity were passively watching in disbelief what was going on, within plotters two fractions appeared- “software-oriented” and “hardware-oriented”. A bit younger than their teachers, very enthusiastic and full of ideas, both of them kept on working but separate ways. While the first group had a stable development, hardware-oriented people, driven by success, soon threw caution to the wind and invented transistor.
Up till that moment, the things could be more or less kept under control, but broad publicity was not aware of seriousness of the situation and it soon led to a fatal mistake! Being naive in belief that using cheap tricks could slow down technology development as well as developing of the world, mass market opened its door to the products of Electronics Industry, closing a magic circle therefore. Components’ prices fell rapidly becoming available for use to younger population. The stone was falling freely...
The first integrated circuits and processors have soon appeared, which enabled for computers to drop down in price. The computers have started to develop their own production. The prices dropped down again and Electronics got new adherents. It appeared everywhere. Another circle has been closed! Ordinary people got hold of computers and computer era has begun...