23-05-2012, 05:05 PM
Electronic sirens incorporate circuits
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Introduction
Electronic sirens incorporate circuits such as oscillators, modulators, and amplifiers to synthesize a selected siren tone (wail, yelp, pierce/priority/phased, hi-lo, scan, air horn, manual, and a few more) which is played through external speakers. It is not unusual, especially in the case of modern fire engines, to see an emergency vehicle equipped with both types of sirens. Often, police sirens also use the interval of a triton to help draw attention.
Project Overview
This police siren simulated electronic project uses two 555 timers IC to generate a sound similar to the police siren. A single 556 timer IC which consists of two 555 timers can also be used. In this project, both of the timers are configured as astable circuit. The first timer is configured as a square wave close to 1 Hz astable oscillator. The output of this timer is used to feed the control voltage of the second timer where it is subjected to frequency modulation. This frequency modulation will generate a tone similar to the siren used by the police. The frequency of this tone generator can be varied by changing the value of potentiometer VR1. When set to its maximum value of 220k ohm, it will have a tone frequency of approximately 320 Hz.
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Objective
The main objectives for the project:
I. To learn and familiar with the construction, designing and operation of 555 timer
II. Act to maximise the use full of 555 timer on the system.
III. To make use of electronics knowledge and apply it practically.
Project Outline
In this final report, it contains of five chapters which are introduction, literature review, methodology results & discussion, and conclusion. In the first chapter, which is introduction, it was describe about what type of project. In chapter two, literature review, it describes the information and knowledge from this project. In chapter three, methodology, it describes the procedure from starting till the end of the process of the project. The Next chapter is results and simulation that we obtain from both software and hardware and compare it. The Last chapter in this report is conclusion, it summarises and describe of future improvement of this project.
LITRTATURE REVIEW
Introduction
In completing this project, some literature reviews have been done on several resources. The theory and description plus details about the project have taken as guidance in completing this project. By this chapter, an overview of some application that similar to the project and related project design is present.
555 Timer
The LM555 is a highly stable device for generating accurate time delays or oscillation, and was also the very first and only commercial IC timer available Additional terminals are provided for triggering or resetting if desired. In the time delay mode of operation, the time is precisely controlled by one external resistor and capacitor. For Astable operation as an oscillator, the free running frequency and duty cycle are accurately controlled with two external resistors and one capacitor. The circuit may be triggered and reset on falling waveforms, and the output circuit can source or sink up to 200mA or drive TTL circuits.