ABSTRACT
This project, 555 Timer IC Based Detonator, is intended to use the switching mechanism of the 555 timer IC to established time variants for the triggering and blasting of a suitably used material, gunpowder. It makes use of the monostable mode of connection or wiring of the 555 timer to establish this. Different stages of triggring of the material is provided, and each goes through a relay switch that closes its terminal to send high current to a short-circuited piece of nichrome material – a wire. At the establishment of a short the nichrome glows at red hot immediately. This heat is strong enough to ignite the gunpoweder and start of the spontaneous chemical reaction that gives off visible light and loud explosion. To incorporate some protective measure against illicit or third party hacking, these triggering have been employed: 555 timer primary detonation, which is the normal operation of the IC, Light-exposure detonation, which is possible through the use of a light sensor that quickly allows huge current to pass through it when light is incident on it, Wrong defusing detonation, which is a technique that when a wrong wire is cut in attempt to disarm the setup the detonator triggers an explosion, Emergency detonation, which is used directly, bypassing the other triggering techniques.
TABLE OF CONTENTS
Title Page i
Declaration ii
Dedication iii
Certification iv
Acknowledgement v
Table of Contents vi
CHAPTER 1: INTRODUCTION
1.1 background of the Study 1
1.2 Aims and Objectives 3
1.3 Problem Statement 3
1.4 Significance of the Study 5
1.5 Scope and Limitation 5
1.6 Project Organisation 5
CHAPTER 2: LITERATURE REVIEW
2.1 Traditional Mechanism 6
2.2 Detonation Techniques Approaches 8
2.3 Electronic Detonators 10
2.4 Triggering 10
2.5 Triggering Techniques 19
CHAPTER 3: MATERIALS AND METHODS
3.1 Theory of Components 23
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Continuity and Resistance of Board 41
4.2 Continuity of Connecting Wires 41
4.3 Consumables Test 41
4.4 Relay Testing 43
4.5 Testing Instruments 44
4.6 Gunpowder (Black Powder) 45
4.7 Installation 45
CHAPTER 5: CONCLUSION AND RECOMMENDATION
5.1 Conclusion 47
5.3 Recommendation 48
References
LIST OF TABLES
3.1 Components specifications and ratings 37
3.2 Components costs 38
LIST OF FIGURES
2.1: Effect of surface area exposed 7
2.2: LM9805 IC voltage regulator 12
2.3: 555 Timer pins 13
2.4: Internal structure of 555 timer IC 15
2.5: Monostable Operation 16
2.6: Project circuit diagram 17
2.7: SPDT relay working 18
2.8: Light-exposure detonation 21
2.9: Wrong defusing detonation 22
3.1: Resistors 24
3.2: Configuration of SPST, SPDT, DPST and DPDT 27
3.3: Veroboard (Copper-stripped board) 29
3.4: 555 Timer pins 30
4.1: Circuit block diagram 39
4.2: Project circuit diagram 40
CHAPTER 1
INTRODUCTION
1.1 BACK GROUND OF THE STUDY
A detonator is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the latter two being the most common. Since the invention of Gunpowder in 1860 by Alfred Nobel mining industry (as well as several other industries, organisation, military and security defenses etc.) was in need of initiating devices which helps in increasing blast size, improve safety during charging & blasting operation, as well as explosive performance. From Plain detonators & Safety fuse system to Shock-tube initiation system, commercial basting has helped the above cause. However each system has some limitation in terms of accuracy of delay, safety requirement as well as complexity required in terms of blast requirement of modern mining industry. Electronic Delay Detonators have come a long way since their invention in late 90s. They have helped Blasting Engineers in solving modern detonation and blasting requirement of Large blast with minimum Vibration, Better control on fragmentation, Blasting multi-layer rock together, controlling throw & back break, and for other operation. Manoj and Suresh (2006)
The commercial use of explosives uses electrical detonators or the capped fuse which is a length of safety fuse to which an ordinary detonator has been crimped. Many detonators' primary explosive is a material called ASA compound. This compound is formed from lead azide, lead styphnate and aluminium and is pressed into place above the base charge, usually Trinitrotoluene TNT or tetryl (an explosive compound) in military detonators and PETN (an explosive material in commercial detonators).
Other materials such as DDNP (diazo dinitro phenol) are also used as the primary charge to reduce the amount of lead emitted into the atmosphere by mining and quarrying operations. Old detonators used mercury fulminate as the primary, often mixed with potassium chlorate to yield better performance.
A blasting cap is a small sensitive primary explosive device generally used to detonate a larger, more powerful and less sensitive secondary explosive such as TNT, dynamite, or plastic explosive.
Blasting caps come in a variety of types, including non-electric caps, electric caps, and fuse caps. They are used in commercial mining, excavation, and demolition. Electric types are set off by a short burst of current conducted from a blasting machine by a long wire to the cap to ensure safety. Traditional fuse caps have a fuse which is ignited by a flame source, such as a match or a lighter.
Detonators have been produced to curb the dangers associated with directly exploding materials or chemical compounds that explode when exposed to pressure, heat, electricity etc. In all forms of detonation, a technique is devised to time the detonation of the substance in question. This timing is also applicable to the traditional use of lengths of gunpowder poured or sprayed continuously along the floor to a containing chamber or housing. The knowledge of the timing is also used in other forms of modern detonators to achieve similar results.
This project focuses on electrical detonation approach of devices or substances, using series of components: the 555 timer in monostable operation, where the circuit consists of 2 switches one for starting the delay time and the other for resetting, a potentiometer can be used to set delays, from where you can increase or decrease the time delay by just rotating suitably a potentiometer or some array of fixed resistors, capacitors, diodes, transistors etc. This employs the use of a voltage source of 9 V and 5V relay for switching or engaging mechanically the substance to be detonated. A 5V voltage regulator Integrated Circuit IC is used for giving 5V regular supply to the circuit. Monitoring devices like LEDs (light-emitting diodes, buzzers etc.) are used. They also function as warning signals for flight. The 5V relay closes as the 555 timer establishes the timed current signal. This current through the relay is sufficient enough to close it and allow current from a different source to the nichrome element buried inside the detonating substance. The element produces excessive heat which triggers the substance into explosion.
The power sources are two independent and physically isolated direct current DC sources: one for working the detonator and the other for sending the required current through a relay to the nichrome element in the explosive substance.
This finds application wherever such will be needed, be it in felling structures, mining exploration, military use etc.
1.2 AIMS AND OBJECTIVES OF THIS PROJECT
The aim of this project is to design and construct a 555 Timer IC Based Detonator whose objective it to use the timing ability of the 555 Timer Integrated Circuit to establish an output voltage through the pin 3 of the IC and close an electromechanical relay connected to the IC. Once this is achieved, the output terminals of the relay are closed to short out or bridge a high power power source and generate red heat or flame.
1.3 PROBLEM STATEMENT
The need for detonators came from the development of safer explosives. Different explosives require different amounts of energy (their activation energy) to detonate. Most commercial explosives are formulated with a high activation energy, to make them stable and safe to handle so they will not explode if accidentally dropped, mishandled, or exposed to fire. These are called secondary explosives. However they are correspondingly difficult to detonate intentionally, and require a small initiating explosion. This is provided by a detonator.
A detonator may contain an easy-to-ignite primary explosive that provides the initial activation energy to start the detonation in the main charge. Explosives commonly used in detonators include mercury fulminate, lead azide, lead styphnate etc. Blasting caps (a small sensitive primary explosive device generally used to detonate a larger, more powerful and less sensitive secondary explosive such as TNT, dynamite, or plastic explosive etc. ) and some detonators are stored separately and not inserted into the main explosive charge until just before use, keeping the main charge safe.
Detonators are hazardous for untrained personnel to handle since they contain primary explosive. They are sometimes not recognized as explosives due to their appearance, leading to injuries.
To combat this challenge and to ensure more safety, electrical detonators can be easily and more simply employed – but not to say that primary explosives are absolutely eliminated. Watson, William (1745) There are three categories of electrical detonators: instantaneous electrical detonators (IED), short period delay detonators (SPD) and long period delay detonators (LPD). SPDs are measured in milliseconds and LPDs are measured in seconds. In situations where nanosecond accuracy is required, specifically in the implosion charges in nuclear weapons, exploding-bridgewire detonators are employed. The initial shock wave is created by vaporizing a length of a thin wire by an electric discharge. A new development is a slapper detonator, which uses thin plates accelerated by an electrically exploded wire or foil to deliver the initial shock. It is in use in some modern weapon systems. A variant of this concept is used in mining operations, when the foil is exploded by a laser pulse delivered to the foil by optical fiber.
Similarly, this project uses similar approach, employing a nichrome element, which when sufficient electrical current passes through it glows at red heat and may cut or melt. The heat generated in the element is all that is needed to trigger off the explosion of the substance. In this case, the substance used is gunpowder. The nichrome material eliminates the need for a primary explosive. So the detonator, separated from the substance to be exploded, is totally safe to handle or carry about.
All electric detonators are specially designed to provide the precise control necessary to produce accurate and consistent blasting results.
1.4 SIGNIFICANCE OF THE STUDY
This is to construct a 555 Timer IC Based Detonator which is inexpensive, safe and efficient, that can preferably be used for blasting purposes or security measures in the military, to detonate gunpowder or similar explosives, and affordable to the public and private sectors.
1.5 SCOPE AND LIMITATION
In this project, I employ the use of electrical detonation approach to detonate a substance in the order of gunpowder, a knowledge gained from theoretical as well as practical experiences from the Institution and beyond.
A 555 timer in its monostable connection is used to produce the signals needed which are varied and timed by a combination of resistors and capacitors. The output of the timer is incorporated into a relay which closes to allow the passage of huge currents through its other terminals to a nichrome element buried in the gunpowder.
The major limitations are the inherent delay associated with the material of the gunpowder as it reacts with heat, in that there are some milliseconds to about 2 seconds delay before detonation is successfully achieved; the milliseconds delay of the relay before the terminals close or open.
1.6 PROJECT ORGANISATION
The layout of the project is in five chapters:
Chapter One focuses on the introduction, which contains the background of the study, problem statement, aim and objectives of the project, significance as well as the scope.
Chapter Two addresses the literature review. Chapter three discusses the theory of components, giving relevant information about the design and calculations necessary to achieve desired result. Chapter four gives information on the physical construction and testing. Chapter Five is the summary and conclusion and also states some recommendations.
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