Voltmeter Construction

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ABSTRACT

The objective of this project is to design LCD digital oscilloscope for practical use. The basic concept for the project involves reading the voltage signal at the input and displaying it on the screen of an alphanumeric LCD. The input analog signals are supplied to the ADC(Analog to Digital Converter), which are then sampled by it and the amplitude of the signal(voltage) is displayed on the LCD.

Device Components:

Microcontroller or processor:

We used Atmega16- an Atmel AVR series microcontroller. The processor clock was set to 11MHz internal oscillator.

Analog to Digital Converter:

In this device we use Atmega16’s inbuilt analog to digital converter. It is a 10-bit ADC which uses the in-built reference voltage level of 2.5V.

Software Implementation:

The programming required, reading the input signal from the ADC pin and then to display the voltage on the alphanumeric LCD, is done using Bascom-AVR.

Though the features of an actual oscilloscope have been compromised upon but the essence of its hardware has been conserved by implementing a voltage reading device.

CHAPTER-1

INTRODUCTION

The oscilloscope is one of the most important tools to be used by any electronics hobbyist but not everyone can afford to have one. As commercial scopes are often too expensive, almost every electronics hobbyist thought at a certain time to build one from scratch. The classical oscilloscope (cathode ray tube) is difficult to build at home because of its size, mechanical fragility, high voltage presence, etc. An alternative solution is the modern “PC oscilloscope”, having the advantage of post processing and recording capabilities, and kind of reduced complexity. However, this solution is often non-portable, expensive (requires a PC) and dangerous for the PC if not isolated from its chassis. The third solution is commonly used these days by all commercial oscilloscope manufacturers, is the digital oscilloscope with LCD screen. Therefore we decided to use this solution and tried to develop it using common parts from today’s component retailers.

The objective of this project is to design LCD digital oscilloscope for practical use. The basic concept for the project involves reading the voltage signal at the input and displaying it on the screen of an alphanumeric LCD. The input analog signals are supplied to the ADC(Analog to Digital Converter), which are then sampled by it and the amplitude of the signal(voltage) is displayed on the LCD.

Hardware used:

• Atmega16 microcontroller

• JHD162A LCD module

• Resistors

• Crystal

• Capacitors

Software used: Program written in BASIC

CHAPTER-2

OSCILLOSCOPE

An oscilloscope is a test instrument which allows you to look at the 'shape' of electrical signals by displaying a graph of voltage against time on its screen. It is like a voltmeter with the valuable extra function of showing how the voltage varies with time. A graticule with a 1cm grid enables you to take measurements of voltage and time from the screen.

The graph, usually called the trace, is drawn by a beam of electrons striking the phosphor coating of the screen making it emit light, usually green or blue. This is similar to the way a television picture is produced.

Oscilloscopes contain a vacuum tube with a cathode (negative electrode) at one end to emit electrons and an anode (positive electrode) to accelerate them so they move rapidly down the tube to the screen. This arrangement is called an electron gun. The tube also contains electrodes to deflect the electron beam up/down and left/right.

The electrons are called cathode rays because they are emitted by the cathode and this gives the oscilloscope its full name of cathode ray oscilloscope or CRO.

A dual trace oscilloscope can display two traces on the screen, allowing you to easily compare the input and output of an amplifier for example. It is well worth...
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