Since the main intension of this project is to design a HAND HELD VEHICLE LOCK CONTROL SYSTEM USING WIRELESS COMMUNICATION. In order to fulfill this application there are few steps that has been performed i.e.
1) Designing the power supply for the entire circuitry.
2) Selection of microcontroller that suits our application.
3) Selection of TV remote and receiver
Complete studies of all the above points are useful to develop this project.
POWER SUPPLY SECTION
In-order to work with any components basic requirement is power supply. In this section required voltage level is 5V DC power supply
Now the aim is to design the power supply section which converts 230V AC in to 5V DC. Since 230V AC is too high to reduce it to directly 5V DC, therefore we need a step-down transformer that reduces the line voltage to certain voltage that will help us to convert it in to a 5V DC.
Considering the efficiency factor of the bridge rectifier, we came to a conclusion to choose a transformer, whose secondary voltage is 3 to 4 V higher than the required voltage i.e. 5V. For this application 0-9V transformers is used, since it is easily available in the market.
The output of the transformer is 9V AC; it feed to rectifier that converts AC to pulsating DC.
As we all know that there are 3 kind of rectifiers that is
1) half wave
2) Full wave and
3) Bridge rectifier
Here we short listed to use Bridge rectifier, because half wave rectifier has we less in efficiency. Even though the efficiency of full wave and bridge rectifier are the same, since there is no requirement for any negative voltage for our application, we gone with bridge rectifier.
Since the output voltage of the rectifier is pulsating DC, in order to convert it into pure DC we use a high value (1000UF/1500UF) of capacitor in parallel that acts as a filter. The most easy way to regulate this voltage is by using a 7805 voltage regulator, whose output voltage is constant 5V DC irrespective of any fluctuation in line voltage.
SELECTION OF MICROCONTROLLER
As we know that there so many types of micro controller families that are available in the market.
- 8051 Family
- AVR microcontroller Family
- PIC microcontroller Family
- ARM Family
Basic 8051 family is enough for our application; hence we are not concentrating on higher end controller families. In order to fulfill our application basic that is AT89C51 controller is enough. But still we selected AT89S52 controller because of inbuilt ISP (in system programmer) option.
There are minimum six requirements for proper operation of microcontroller.
- power supply section
- pull-ups for ports (it is must for PORT0)
- Reset circuit
- Crystal circuit
- ISP circuit (for program dumping)
- EA/VPP pin is connected to Vcc.
PORT0 is open collector that’s why we are using pull-up resistor which makes PORT0 as an I/O port. Reset circuit is used to reset the microcontroller. Crystal circuit is used for the microcontroller for timing pluses. In this project we are not using external memory that’s why EA/VPP pin in the microcontroller is connected to Vcc that indicates internal memory is used for this application.
SELECTION OF TV REMOTE AND IR RECEIVER
In this project I selected PHILIPS TV remote this remote will produce 14 pulses when we press any button. In this two bits are start bits and third is the toggle bit and after 5 bits are the address bits and remaining bits are the data bits
Here in this project we have to read the last 6 bits and according to this data we have to control the robot. In the receiver section I selected TSOP 1738 IR receiver because it is easy way to read the data it has only 3 pins one is ground second is Vcc and the third pin is data through this pin only we have to calculate the data which is transmitted by PHILIPS TV remote.
To implement this application required components are one microcontroller, TV remote, IR receiver (TSOP1738), LCD, BUZZER, l293D and DC motor. Whenever user want to open the door, he has to press one remote switch which is related to ON. For that user has to develop one application program in EMBEDDED-C. At the same time for close the door separate key is assigned. Here whenever door is opened motor will rotate in clockwise direction and BUZZER will ON. At the same time whenever door is closed motor will rotate in anti clock direction and BUZZER will ON.
Embedded systems are electronic devices that incorporate microprocessors with in their implementations. The main purposes of the microprocessors are to simplify the system design and provide flexibility. Having a microprocessor in the device helps in removing the bugs, making modifications, or adding new features are only matter of rewriting the software that controls the device. Or in other words embedded computer systems are electronic systems that include a microcomputer to perform a specific dedicated application. The computer is hidden inside these products. Embedded systems are ubiquitous. Every week millions of tiny computer chips come pouring out of factories finding their way into our everyday products.
Embedded systems are self-contained programs that are embedded within a piece of hardware. Whereas a regular computer has many different applications and software that can be applied to various tasks, embedded systems are usually set to a specific task that cannot be altered without physically manipulating the circuitry. Another way to think of an embedded system is as a computer system that is created with optimal efficiency, thereby allowing it to complete specific functions as quickly as possible.
Embedded systems designers usually have a significant grasp of hardware technologies. They use specific programming languages and software to develop embedded systems and manipulate the equipment. When searching online, companies offer embedded systems development kits and other embedded systems tools for use by engineers and businesses.
Embedded systems technologies are usually fairly expensive due to the necessary development time and built in efficiencies, but they are also highly valued in specific industries. Smaller businesses may wish to hire a consultant to determine what sort of embedded systems will add value to their organization.
Two major areas of differences are cost and power consumption. Since many embedded systems are produced in tens of thousands to millions of units range, reducing cost is a major concern. Embedded systems often use a (relatively) slow processor and small memory size to minimize costs.
The slowness is not just clock speed. The whole architecture of the computer is often intentionally simplified to lower costs. For example, embedded systems often use peripherals controlled by synchronous serial interfaces, which are ten to hundreds of times slower than comparable peripherals used in PCs. Programs on an embedded system often run with real-time constraints with limited hardware resources: often there is no disk drive, operating system, keyboard or screen. A flash drive may replace rotating media, and a small keypad and LCD screen may be used instead of a PC’s keyboard and screen.
Firmware is the name for software that is embedded in hardware devices, e.g. in one or more ROM/Flash memory IC chips. Embedded systems are routinely expected to maintain 100% reliability while running continuously for long periods, sometimes measured in years. Firmware is usually developed and tested too much harsher requirements than is general-purpose software, which can usually be easily restarted if a problem occurs.
There are many different CPU architectures used in embedded designs. This in contrast to the desktop computer market which is limited to just a few competing architectures mainly the Intel/AMD x86 and the Apple/Motorola/IBM Power PC’s which are used in the Apple Macintosh. One common configuration for embedded systems is the system on a chip, an application-specific integrated circuit, for which the CPU was purchased as intellectual property to add to the IC’s design.
Like a typical computer programmer, embedded system designers use compilers, assemblers and debuggers to develop an embedded system. Those software tools can come from several sources:
Software companies that specialize in the embedded market Ported from the GNU software development tools. Sometimes, development tools for a personal computer can be used if the embedded processor is a close relative to a common PC processor. Embedded system designers also use a few software tools rarely used by typical computer programmers. Some designers keep a utility program to turn data files into code, so that they can include any kind of data in a program. Most designers also have utility programs to add a checksum or CRC to a program, so it can check its program data before executing it.
They often have no operating system, or a specialized embedded operating system (often a real-time operating system), or the programmer is assigned to port one of these to the new system.
Debugging is usually performed with an in-circuit emulator, or some type of debugger that can interrupt the micro controller’s internal microcode. The microcode interrupt lets the debugger operate in hardware in which only the CPU works. The CPU-based debugger can be used to test and debug the electronics of the computer from the viewpoint of the CPU.
Developers should insist on debugging which shows the high-level language, with breakpoints and single stepping, because these features are widely available. Also, developers should write and use simple logging facilities to debug sequences of real-time events. PC or mainframe programmers first encountering this sort of programming often become confused about design priorities and acceptable methods. Mentoring, code-reviews and ego less programming are recommended.
DESIGN OF EMBEDDED SYSTEMS:
The electronics usually uses either a microprocessor or a microcontroller. Some large or old systems use general-purpose mainframes computers or minicomputers.
All embedded systems have start-up code. Usually it disables interrupts, sets up the electronics, tests the computer (RAM, CPU and software), and then starts the application code. Many embedded systems recover from short-term power failures by restarting (without recent self-tests). Restart times under a tenth of a second are common.
Many designers have found one of more hardware plus software-controlled LED’s useful to indicate errors during development (and in some instances, after product release, to produce troubleshooting diagnostics). A common scheme is to have the electronics turn off the LED(s) at reset, whereupon the software turns it on at the first opportunity, to prove that the hardware and start-up software have performed their job so far. After that, the software blinks the LED(s) or sets up light patterns during normal operation, to indicate program execution progress and/or errors. This serves to reassure most technicians/engineers and some users.
THE CONTROL LOOP:
In this design, the software has a loop. The loop calls subroutines. Each subroutine manages a part of the hardware or software. Interrupts generally set flags, or update counters that are read by the rest of the software. A simple API disables and enables interrupts. Done right, it handles nested calls in nested subroutines, and restores the preceding interrupt state in the outermost enable. This is one of the simplest methods of creating an exocrine.
Typically, there’s some sort of subroutine in the loop to manage a list of software timers, using a periodic real time interrupt. When a timer expires, an associated subroutine is run, or flag is set. Any expected hardware event should be backed-up with a software timer. Hardware events fail about once in a trillion times.
State machines may be implemented with a function-pointer per state-machine (in C++, C or assembly, anyway). A change of state stores a different function into the pointer. The function pointer is executed every time the loop runs.
Many designers recommend reading each IO device once per loop, and storing the result so the logic acts on consistent values. Many designers prefer to design their state machines to check only one or two things per state. Usually this is a hardware event, and a software timer. Designers recommend that hierarchical state machines should run the lower-level state machines before the higher, so the higher run with accurate information.
Complex functions like internal combustion controls are often handled with multi-dimensional tables. Instead of complex calculations, the code looks up the values. The software can interpolate between entries, to keep the tables small and cheap.
One major disadvantage of this system is that it does not guarantee a time to respond to any particular hardware event. Careful coding can easily assure that nothing disables interrupts for long. Thus interrupt code can run at very precise timings. Another major weakness of this system is that it can become complex to add new features. Algorithms that take a long time to run must be carefully broken down so only a little piece gets done each time through the main loop.
This system’s strength is its simplicity, and on small pieces of software the loop is usually so fast that nobody cares that it is not predictable. Another advantage is that this system guarantees that the software will run. There is no mysterious operating system to blame for bad behavior.
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