Remote Locator

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We know that as technology is growing more and more equipment are being developed. In laboratories there will be many instruments and equipments kept in big rooms and out of them few will be used frequently, some are used occasionally. Naturally human tendency is that after the complete usage of instruments or equipments they will not be place them in right order and correct location. Hence it becomes difficult to locate them immediately when they are required again. Our project intends to eliminate this problem.

The objective of the project is to develop such a system, which can identify and indicates the location of the instruments and equipments in laboratories.


1. Introduction

2. Functional Block Diagram

3. Functional Description

4. Introduction to AT 89C51

5. Hardware

5.1 Power Supply

5.2 L C D

5.3 ASK Tx and Rx

5.4 MATRIX keypad

5.5 Relay Driver Circuit Using ULN 2003

6. Software

6.1 Flow Chart

6.2 Program




The main motivation behind bringing our project entitled MICROCONTROLLER BASED INSTRUMENT IDENTIFICATION AND DETECTION is the careless nature of the human beings after the work is done. We know that it is the human tendency to misplace the things after the work is done rather than placing them in predefined order so that we can get it easily whenever it is required again. If not placed in order difficulty arises while searching. In the case of a small firm or laboratory searching is not a problem but for the case of big laboratory searching kills lot of time which is not good. This project enables to find the misplaced thing without actually wasting lot of time.


Assuming that, if we have large laboratory with large number of different instruments and equipments arranged in some specific order, and if we need a particular thing, it is bit difficult to search in a big arrangement. Instead of that, if we enter the category ID of the equipment, through keyboard, then that will be encoded and transmitted through the ASK transmitter. Then at the other side this signal will be received and decoded, and decoded data will be read by the controller and it searches for particular equipment to give the indication by means of sound beep.Functional Block Diagram:



Functional Description:



Computer in its simplest from needs at least three basic blocks: the central processing unit (CPU). Input-output (I/O) and memory (RAM/ROM). The integrated from of CPU is the microprocessor. As the use of microprocessors in control applications increased, development of microcontroller unit or MCU took shape, wherein CPU, I/O and some limited memory on a single, chip was fabricated. Intention was to reduce the chip count as much as possible. There are many types of microcontrollers currently in the market, out of which the 8031. Family from Intel, and second soured by many others, have gained immense popularity.


Looking back into the history of microcomputers, one would at first come across the development of microprocessor, I.e.., the processing element, and later on the peripheral devices. The three basic element the CPU, I/O devices and memory- have developed in distinct direction. While the CPU has been the proprietary item, the memory devices fall into general-purpose category and the I/O devices may be grouped somewhere in- between. The control applications of microprocessors have different requirements, both hardware-wise as well as software-wise. Whereas microprocessor has just sufficient number of on-chip devices to act as the CPU, a number of other auxiliary devices are needed to get a working microcontroller. integration of I/O and memory with the CPU on a single chip ushered in the era of development of a new class of devices, i.e..., the single chip microcontrollers. Now only one device was needed to run an independent control application. The 8048 from Intel, Z80 from Zilog, 6805 and 6811 from Motorola represent a few of the members of this large family. The 8048 from Intel became popular due to its use in the keyboard of the IBM PC.

The family of second generation microcontrollers from Intel, the 8051 and other related devices, has brought about a new revolution in this field. While the early microcontrollers had only limited memory and existent serial I/O capability, the 8051 provides for 4k PROM/ROM, 128 byte RAM and 32 I/O lines. It also includes a universal asynchronous receive-transmit (UART) device, two 16-bit timer/counter and elaborate Interrupt logic. Lack of multiply and divide instructions, has also been taken care of in the 8051. Thus the 8051 may be called nearly equivalent of the following devices on a single chip:

8085 + 8255 + 8251 + 8253 + 2764 + 2764 + 6116

(Microprocessor) (PPI) (USART) (TIMER) (EPROM) (RAM)

In short, the 8051 has the following on-chip facilities:

4k ROM (EPROM on 8751)

128 byte RAM


32 Input-output port lines

TWO 16-bit timer/ count

Six interrupt sources and

On-chip clock oscillator and power on- reset circuitry.

The other members of this family, such as 8053, have one extra timer/counter, 8k ROM/EPROM and 256 byte RAM, while 8031and 8032 are corresponding ROM-less versions of 8052,respectivily. All these are also available in CMOS versions. The 8051 family includes a large numbers of members from many manufacturers, some of which are listed below.

8051 with 4k ROM and its

8751 with 4k EPROM

8031 ROM-less version.

8052 with 8k ROM, one additional counter/timer and 256-bit RAM; its other version (8052h) comes with built-in BASIC interpreter.

8032 & 8752 are ROM + I/O (80C31) Along with pulse width modulator.

80C592 With 8-channel A/D converter, by Philips.

AT 89C51 CMOS device with EPROM (100 times programmable), by ATMEL.


The 8051 can be configured to bypass the internal 4k RAM and run solely with external program memory. For this its external access ( ) pin 31 has to be grounded, which makes it equivalent to 8031. The program store enable (PSEN) signal acts as read pulse for program memory. The data memory is external only and a separate RD* signal is available for reading its contents.

Use of external memory requires that three of its 8-bit ports (out of four) are configured to provide data/address multiplexed bus, Hi address bus and control signals related to external memory use. The RXD and TXD ports of UART also appear on pins 10 and 11 of 8051 and 8031, respectively. One 8-bit port, which is bit addressable and extremely useful for control applications, still remains free for use.

The UART utilizes one of the internal timers for generation of baud rate. The crystal used for generation of CPU clock has therefore to be chosen carefully. The 3.579MHz crystal; available abundantly, can provide a baud rate of 1200.

The 256-byte address space is utilized by the internal RAM and special function registers (SFRs)array which is separate from external RAM space of 64k. the 00-7f space is occupied by the RAM and the 80-FF space by the SFRs. The 128-byte internal RAM has been utilized in the following fashion:

00-1F: Used for four banks of eight registers of 8-bit each. The four banks may be selected by soft ware any time during the program.

20-2F: The 16 bytes may be used as 128 bits oriented programs.

30-7F This area is used for temporary storage, pointers and stack. On reset, the stack starts at 08 and gets incremented during use.

The list of special function registers along with their hex addresses is given in table 1.


The on-chip oscillator of 8031 can be used to generator system clock. Depending upon version of the device, crystals from 3.5 to 12 MHz may be used for this purpose. The system clock is internally divided by 6 and the resultant time period becomes one processor cycle. The instructions take mostly one or two processor cycles. The ALE (address latch enable) pulse rate is 1/6th of the system clock, except during access of internal program memory, and thus can be used for timing purposes.

The two internal timers are wired to the system clock and persecuting factor is decided by the software apart from the count stored in the two bytes of the timer control registers. One of the counters, as mentioned earlier, is used for generation of baud rate clock for the UART. It would be of interest to point out that the 8052 has a third timer which is usually used for generation of baud rate.

The reset input is normally low and taking it high reset the microcontroller. In the present hardware, a separate CMOS circuit has been used for generation of reset signal so that it could be used to drive external devices as well.



Circuit ground potential.


5-volt power supply input for normal operation and program verification.


Port o is an 8-bit open drain BI directional input output port. It is also the multiplexed low ordered address and data bus when using external memory. it is used for data output during program verification Port 0 can sink (and in bus operations can source) 8 LSTTL loads.


Port 1 is an 8 bit quasi bi-directional I/o port. It is also used for low order