Design And Construction Of A Mains Box Heat Monitor

ABSTRACT

This work is on “mains box heat monitor circuit” which monitors the mains distribution box constantly and sounds an alarm when it senses a high temperature due to overheating, helping to prevent disasters caused by any sparking in the mains box due to short circuits. It also automatically switches on a bright white LED when the power fails. The LED gives ample light to check the mains box wiring or fuses in darkness. The circuit beeps once when power fails and again when power resumes.

TABLE OF CONTENTS

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

1.0      INTRODUCTION

1.1      BACKGROUND OF THE PROJECT

1.2      AIM OF THE PROJECT

1.3      OBJECTIVE OF THE PROJECT
1.4      SIGNIFICANCE OF THE PROJECT

1.5      PURPOSE OF THE PROJECT

1.6     APPLICATION OF THE PROJECT

1.7    ADVANTAGES OF THE PROJECT

1.8      PROBLEM/LIMITATION OF THE PROJECT

1.9      PROJECT ORGANISATION

CHAPTER TWO

2.0     LITERATURE REVIEW

2.1      REVIEW OF RELATED TERMS

CHAPTER THREE

3.0     CONSTRUCTION METHODOLOGY

3.1      SYSTEM CIRCUIT DIAGRAM

3.2     SYSTEM OPERATION

3.3      CIRCUIT DESCRIPTION

3.4      SYSTEM CIRCUIT DIAGRAM

3.5      CIRCUIT OPERATION

3.6      IMPORTANCE AND FUNCTION OF THE MAJOR COMPONENTS USED

3.7      POWER SUPPLY UNIT

CHAPTER FOUR

RESULT ANALYSIS

4.0      CONSTRUCTION PROCEDURE AND TESTING

4.1      CASING AND PACKAGING

4.2      ASSEMBLING OF SECTIONS

4.3      TESTING

4.4.1 PRE-IMPLEMENTATION TESTING

4.4.2  POST-IMPLEMENTATION TESTING

4.5      RESULT

4.6      COST ANALYSIS

CHAPTER FIVE

5.0      CONCLUSION

5.1      RECOMMENDATION

5.2      REFERENCES

                                                             BLOCK DIAGRAM

Before carrying out any project, the block diagram must be drawn and fully understood. Block diagram gives a pictorial understanding of any work. The block diagram of the system is as below:

Mains Box Heat Monitor Circuit

The AC mains is stepped down by transformer X1 to deliver a secondary output of 9V AC at 500 mA. The transformer output is rectified by diodes D1 through D4. Capacitor C1 bypasses the ripple. LED1 indicates the power-on condition. Resistor R1 acts as the current limiter for LED1.

Germanium diode D5 (1N34) is the temperature sensing element, which is connected in the reverse bias mode. At normal temperature, the resistance of the diode is high and, as a result, transistor T1 conducts to hold reset pin 4 of IC1 in low state.

Mains Box Heat Monitor Circuit

NE555 (IC1) is wired as an astable multivibrator. When the temperature around diode D5 rises due to overheating of the fuse, the resistance of the diode decreases and transistor T1 stops conducting. This enables IC1 and the oscillator starts to sound an alarm. By adjusting preset VR1, you can set the temperature level at which the alarm circuit is activated.

The emergency light circuit uses pnp transistor BC558 (T2) and a few passive components. It is powered by a 9V rechargeable battery, which is constantly charged via forward-biased diode D6 when mains power is present. Resistor R7 reduces the charging current to a safer level. The forward biasing of diode D6 results in reverse biasing of transistor T2 and thus the white LED (LED3) is off. When the power fails, transistor T2 is forward biased and lights up the LED. When the power resumes, transistor T2 stops conducting and the LED doesn’t glow.

Construction & testing

The circuit can be easily constructed on any general-purpose PCB. Diode D5 should be placed close to the fuse to sense the heat. It can be connected to the PCB using a short piece of shielded wire. The white LED should be directed towards the fuse such that the maximum light falls on the fuse.

To test the circuit, take the hot tip of the soldering iron near diode D5. The buzzer will sound to indicate the high temperature.

Mains box heat monitor using 555 Timer IC

Here is a simple circuit mains box heat monitor for sensing high temperature due to overheating. This circuit helps to prevent disasters caused by only sparking in the mains box due to any fault like short circuit over loaded. This circuit is so designed that it also automatically switches on a bright while LED (LED₃) in case of power fails. This light is sufficient to check the mains box wring or fuses in darkness.

Circuit Description Mains Box Heat Monitor

The circuit is build around timer IC, a sensor and two transistors. The input AC mains is stepped down by using a 0-9v 500mA transformer and rectified by using bridge rectifier build using four diodes D₁ through D_4. The rectified voltage is further filtered by using 1000 µF of capacitor (C₁) to smoothen the voltage and bypass the ripple. The output is given to LED₁ through resistor R₁ to indicate the power-on condition. Resistor R₁ is used here as correct limiter.

Diode D₅ is a germanium diode which is here act as temperature sensor and is used in reverse bias mode. The resistance of diode D₅ is high at normal temperature areal as a result transistor T₁ conducts to hold pin 4 of IC₁ in low state. Potentiometer VR₁ is used hear for adjust sensing capability of circuit.

Timer IC (IC₁) is configured here as an astable multivibrator and generate frequency when the temperature around diode D₅ rise due to overheating of the fuse. The resistance of diode D₅ is decrease when temperature rise and transistor T₅ stop conducting and this enable IC₁. The output of IC₃ is given to LED₂ through resistor R₆ for visual indication. A piezo buzzer (PZ) is connected parallel to LED₁ as shown in circuit diagram for audio indication.

The emergency light circuit is build around PNP transistor (T₂). It is powered by a 9V rechargeable battery. The battery B₁ is also charged constantly via forward bias diode D₆ in mains on condition. The forward bias of diode D₆ results in reverse biasing of transistor T₂ and thus white LED (LED₃) is off. Similarly in absence of mains transistor T₂ is forward bias and light up the LED (LED₃)

The circuit beeps once when power fails and again when power resumes.

BEP NOTE: Diode D₅ should be placed close to the fuse and the LED₃ should be directed towards the fuse such the maximum lights falls on the fuse. In BEP LAB we test the circuit by putting the hot tip of soldering iron near diode D₃. The piezo buzzer PZ₁ will sound to indicate the high temperature.

PARTS LIST OF MAINS BOX HEAT MONITOR