**ABSTRACT**

A resistor colour code calculator is an electronic
system that calculates the resistance of a resistor simply by pressing the keys
that correspond to the colour code. The system consist of five basic stages,
the key board which accepts the input command, the encoder which receives the
command from the key board and forms a corresponding binary code from the
encoder, the BCD to 7 segment decoder which reverses the binary code from the
memory and forms a comprehensive code which then displays by light emitting
diode (LED) sensor.

Input decimal signals from the input keys are connected to
a corresponding binary code by the diode matrix (encoder) this code are the
inverted and stored in the memory unit (flip-flop) the BCD to decimal 7-segment
decoder is an I.C of the SN 74 family which then rearrange the BCD Code to
7-segment arrangement which is as follows: - All the input keys are coloured to
represent the colour of the resistor code (Black-White) When a key is pressed a
code is formed which represent the code of that colour (e.g. Red = 2), To
compute the resistance of a given resistor, the color of the first band is
entered to the first channel which counts, decodes and display numeric value on
the channel display digit. The second and the third follow the same sequence.
The combine display of the three digits on the display gives the value of the
resistor.

**CHAPTER ONE**

**1.0**

**INTRODUCTION**

An electronic calculator is a small, portable electronic
device used to perform both basic and complex arithmetic operation on numbers.
The abacus was one of the first mathematical devices to be used, and it is
simply a series of beads or stones that represent numbers. It wasn’t until 1623
that the first calculating machine was designed by Wilhelm Schiekard.

This chapter
introduces the resistor colour code calculator. It covers the advantages of
using the calculator to calculate the resistance of a carbon resistor using its
colour band.

**Types of Calculator**

1.

**Basic Calculator:**a basic keypad, calculator, similar to a small handheld calculator, for addition, subtraction, division and multiplication. Just a basic calculator for basic calculations and memory functions programmable
2.

**Scientific Calculator:****Functions:**fractions (SIN/COS/TAN)

**Suitable for:**statistical calculations (www.wikipedia-calculator.com 2013).

3. Financial
Calculator

**Functions:**conversion

**Suitable for:**studying financial management (www.campbellp;com (2014)

4. Graphic
Calculator: a graphing calculator (graphic calculator) is a handheld calculator
that is capable of plotting graphs, solving simultaneous equations. Most
popular graphing calculators are also programmable, allowing the user to create
customized programs.

**1.1**

**PREAMBLE**

A resistor is a component of an electrical circuit
that offers opposition to the flow of current. They are described by stating
their resistance in ohms along with their safe power dissipating ability in
Watt.

Resistors may be classified in different categories;
by use of this could be classified as; power resistors, instrument resistor,
and resistors of electronic circuit. By construction, they could classified as
composition resistors, film resistors and wire resistors (Oison, 1909).

A carbon resistor is a resistor of electronic by use,
and a composition resistor by construction. It consist of a finely ground
carbon particles mixed with a ceramic material, encapsulated into insulated
tube. The casing has a set of coloured strips denoting the value of the
resistance. This colour represents numeric numbers from 0-9. To calculate the
value of resistance, the first colour value is placed with the second and both
multiplied by the third called the multiplier (this will be treated fully in
chapter two). (Preston and Walter, 1960).

For easier, faster and more reliable and efficient
calculation, the digital code calculator is design. This is a digital machine
that computes the value of the resistor by simply punching coloured keys on a
keypad.

It consist basically of a digital (logic) circuit that processes the
information entered in the keypad which contains keys with colours representing
the ten standard colours of the carbon resistors, and a LED display unit which
clearly shows the value in digital readable seven segment form. This system
helps to eliminate errors associated with manual formula-based calculations
which involve correct memorizing of the colour codes. (James, 1991).

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