DIGITAL COUNTDOWN TIMER

Philip Gerald Jael

John Chamver Puno

Janelle Quianzon

3ITE

INTRODUCTION

An embedded system is a computer system designed for specific control functions within a

larger system, often with real-time computing constraints. It is embedded as part of a

complete device often including hardware and mechanical parts. By contrast, a general-

purpose computer, such as a personal computer (PC), is designed to be flexible and to meet

a wide range of end-user needs. Embedded systems control many devices in common use

today.

Embedded systems are a growing phenomenon in the technology world. Telephone and

communication devices were some the earliest innovators of embedded systems. Today,

governments and industries are putting major financing towards development of new

applications and devices for trains, planes, and automobiles. Embedded systems are also

found in smart cards and many consumer electronics.

The embedded system that the proponents will be making is a countdown timer.

OVERVIEW

A simple count-down LED timer that counts in minutes and seconds. Three buttons below

the LED provide control of the unit, allowing you set the desired countdown time in minutes

and seconds and a start/stop button. Completion of the countdown is indicated by an alarm

that starts when the countdown has finished and the display reads zero. The alarm is

stopped by pressing the start/stop button.

CIRCUIT DIGRAM

PROJECT COSTING

Resistor x 14 = 14

Led x 4 = 200

Breadboard x 2 = 120

Capacitor x 2 = 2

Switch x 3 = 75

AT89C2051 x 1 = 100

Transistor x 4 = 8

Total = 519

IMPLEMENTATION

The proponents will use the following:

The Embedded System would provide a countdown timer which has 3

switches (Reset, Stop and Start).

AT89C2051 IC to store the countdown program.

Breadboard for testing purposes and connection of wires.

Led will be used to show the generated numbers by the IC.

Wires will be used for the connections.

Resistors are used to regulate the voltage in every connection.

SOURCE CODE

HEX CODE GENERATED

TOOLS AND EQUIPMENT USED

Atmel Programmer

Atmel Trainer

Keil uVision 4

AT89C2051

Low-voltage, high-performance CMOS 8-bit microcomputer with 2KB of flash programmable

and erasable read-only memory. The device is manufactured using Atmel high-density

nonvolatile memory technology and is compatible with the industry-standard MCS-51

instruction set. This versatile 8-bit CPU with flash provides a highly flexible and cost-effective

solution for many embedded control applications.

7 – Segment Led Display

A seven-segment display (SSD), or seven-segment indicator, is a form of electronic display

device for displaying decimal numerals that is an alternative to the more complex dot-

matrix displays. Seven-segment displays are widely used in digital clocks, electronic meters,

and other electronic devices for displaying numerical information.

Resistor

A resistor is a linear, passive two-terminal electrical component that implements electrical

resistance as a circuit element. The current through a resistor is in direct proportion to the

voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a

resistor's terminals to the intensity of current through the circuit is called resistance. This

relation is represented by Ohm's law.

Rectifier

A rectifier is an electrical device that converts alternating current (AC), which periodically

reverses direction, to direct current (DC), which flows in only one direction. The process is

known as rectification. Physically, rectifiers take a number of forms, including vacuum tube

diodes, mercury-arc valves, solid-state diodes, silicon-controlled rectifiers and other silicon-

based semiconductor switches.

Transistor

A transistor is a semiconductor device used to amplify and switch electronic signals and

power. It is composed of a semiconductor material with at least three terminals for

connection to an external circuit. A voltage or current applied to one pair of the transistor's

terminals changes the current flowing through another pair of terminals. Because the

controlled (output) power can be much more than the controlling (input) power, a transistor

can amplify a signal.

Capacitor

A capacitor (formerly known as condenser) is a passive two-terminal electrical component

used to store energy in an electric field. The forms of practical capacitors vary widely, but all

contain at least two electrical conductors separated by a dielectric (insulator); for example,

one common construction consists of metal foils separated by a thin layer of insulating film.

Capacitors are widely used as parts of electrical circuits in many common electrical devices.

OPERATING PROCEDURE

1. First put the 4 LED and place its connection.

2. Next is place important parts like capacitor and resistor follow the connection for the

LED.

3. After that put the rectifier connect it to the LED.

4. Make a power supply using a small transformer using wires and a plug.

5. Lastly add the switch to the circuit

6. Test the circuit in the breadboard.

7. If there is no error place it in a circuit board/PCB.

PROBLEMS ENCOUNTERED

Program mismatched

Lack of materials

Wrong placement of wires

Power not turning on

SUMMARY

The goal of this proposed project aims to design, build, and test a countdown timer using

Atmel IC. This project is motivated by the need to expand our knowledge in embedded

systems. To achieve this goal, this project will employ innovative and indigenous materials,

which will help us in our project like the Keil uVision4, Atmel Programmer and Atmel

Trainer. The anticipated outcome of this project will be a countdown timer which has 3

buttons that would be Start, Pause and Stop.

The project will also:

Make an embedded system using AT89C2051/AT89C4051.

Develop a prototype for testing purposes.

Make a countdown timer using AT89C2051.

Make a code for the IC to produce a countdown timer

REFERENCES

http:// www.8051projects.info/proj.asp?id=61

http://technorati.com/technology/embedded/article/embedded-systems-devices-for-

everyday-life/#ixzz1pEJejytX

AT89C2051 Datasheet