Electronic Cloth Line Management Unit Chapter one

ELECTRONIC CLOTH LINE MANAGEMENT UNIT

CHAPTER ONE

STATEMENT OF THE PROBLEM

Clothes lines are common in every home, business premises, schools and hospital among other places. This are meant to dry clothes by natural means when the weather is right. However, due to the many activities handled by the people, clothes are hanged to dry but either delayed or forgotten to remove them when need arises. Rain falls on them and wet them again. Night may fall when the person in charge of them is away or has forgotten. This calls for electronic cloth line management unit. This unit drives the clothes line plus the clothes into the house when rain is sensed and drives the clothes back again when rain ceases. If darkness comes when the rain has not been sensed, the cloth line again drives the cloth line into the house. But if rain had come, the system assumes that the clothes are not dry and retains the clothes outside.

OBJECTIVES

* Design, construct and test electronic cloth line management unit.

* To involve water and light sensors to activate the unit.

* To make use of dc motor in order to drive the line to and fro.

* To use transistor drivers to drive the motor in alternate direction.

SPECIFICATIONS

Operating voltage 12 V dc

Supply voltage 240 V dc

Current 0.5 Ampere

Opening time 20 seconds

Temperature range 00C to 650C

BLOCK DIAGRAM

POWER SUPPLY

Since the circuit is rated to operate from 12 V dc while the mains supply is 240 V ac, there is need for a power supply. This step down voltage from 240v ac to stable 12v dc to power the electronic circuit. This ensures that the voltage supplied to the circuit is stable regardless of variation in mains voltage.

LIGHT SENSOR

This senses light and converts it to electrical signal.

MOTOR CONTROL CIRCUIT

This gives output voltage signals to drive the motor on receiving a signal from light sensor and moisture sensing circuit.

SWITCHING CIRCUIT

This supply power to the motor on receiving signal from the Motor control circuit to run the Clothe line.

MOTOR

This when powered provides the mechanical power to the motor driving the cloth line.

MOISTURE SENSOR CIRCUIT

This detects rain and generates voltage signals to trigger the motor control circuit.

CHAPTER TWO

THEORY OF COMPONENTS

CAPACITORS

Capacitor, sometimes referred to as a Condenser, is a passive device, and one which stores its energy in the form of an electrostatic field producing a potential difference (Static Voltage) across its plates. In its basic form a capacitor consists of two or more parallel conductive (metal) plates that do not touch or are connected but are electrically separated either by air or by some form of insulating material such as paper, mica or ceramic called the Dielectric. The conductive plates of a capacitor can be either square, circular or rectangular, or be of a cylindrical or spherical shape with the shape and construction of a parallel plate capacitor depending on its application and voltage rating.

Capacitor Construction

The unit of capacitance is the Farad (abbreviated to F) named after the British physicist Michael Faraday and is defined as a capacitor has the capacitance of One Farad when a charge of One Coulomb is stored on the plates by a voltage of One volt. Capacitance, C is always positive and has no negative units. However, the Farad is a very large unit of measurement to use on its own so sub-multiples of the Farad are generally used such as micro-farads, nano-farads and pico-farads, for example.

Units of Capacitance

* Microfarad (μF) 1μF = 1/1,000,000 = 0.000001 = 10-6 F

* Nanofarad (nF) 1nF = 1/1,000,000,000 = 0.000000001 = 10-9 F

* Picofarad (pF) 1pF = 1/1,000,000,000,000 = 0.000000000001 = 10-12 F

DIODE

A diode is a two-terminal device, having two active electrodes, between which it allows the transfer of current in one direction only. Diodes are known for their unidirectional current property, wherein, the electric current is allowed to flow in one direction.

Basic Diode Symbol and Static I-V Characteristics.

TRANSFORMER

This is a device used to step down the mains ac mains supply to a lower value required by the circuit, and also to provide isolation between the ac supplies. There are several types of transformers.

Laminated core transformer

This is the most common type of transformer, widely used in appliances to convert mains voltage to low voltage to power electronics

* Widely available in power ratings ranging from mW to MW

* Insulated laminations minimize eddy current losses

* Small appliance and electronic transformers may