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**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**

**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**Scientific Calculator:**- Financial Calculator

**Functions:** conversion

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

- 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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