World University Of Bangladesh A Project on Design And Construction of Anti-Bag Snatching Alarm Submitted by Al-Imran Masum Reg. No: WUB 09/11/47(A)/1491 & Saddam Hossain Reg. No: WUB 09/11/47(A)/1485 Department of Electrical & Electronic Engineering World University of Bangladesh Supervised by Tabassum E Nur Lecturer Department of Electrical & Electronic Engineering World University of Bangladesh Background Nowadays people always remains terrified of snatchers. Day by day it is increasing in a society. Specially, the women are not safe with their purse outside. For this reason, to remove snatching the American inventors Richard W. Dixon invented purse theft alarm on 1971. it was the first use of theft alarm. It was based on the theory that a sudden pull or jerking force exerted by the purse handle will cause the alarm to be actuated. A few years ago, in 2010 Tsang-Chu SHH was invented Burglar proof purse. A burglar proof purse installs a control switch and an alarm for issuing a warning sound at hidden positions of the purse, and a closed and opened loop is distributed all over each surface of the purse and connected to the control switch and the alarm. Executive Summary Here is a very simple as well as very useful project anti bag snatching alarm, used in bag or suitcase in order to prevent from snatching. The heart of this entire circuit anti bag snatching alarm is operational amplifier IC CA3140 (IC1), configured as a comparator. The two inputs (inverting and non – inverting) is given to pin no 3 and 2 of operational amplifier respectively and output is obtained from pin no 6. Here IC2 (timer IC NE555) is used as monostable multivibrator. The timing component of anti bag snatching alarm is R5, VR1, and capacitor C2 with the given value in this circuit diagram lets the time of timer is about 1 minute. For audio section, IC3 is used as alarm tone generator with an inbuilt oscillator. Finally the output is obtained from pin no 3 of IC3 and amplified by transistor T1 in order to get desire level and lastly fed to loudspeaker for output. Objectives To design and construct Anti-Bag snatching alarm for getting rid of snatching and captured the snatchers. To provide a thief alarm device that practically eliminates accidental triggering thereof. Methodology Collection of books, magazines data from different websites. Collection of equipment from local market. Block Diagram of Anti-Bag snatching alarm With 9V power supply Loudspeaker Mono jack & mono Socket Transistor (BD139) Operation Amplifier (CA3140) Complex ROM with an inbuilt oscillator (UM3561) Timer IC (NE555) Circuit Diagram of Anti-bag snatching alarm Internal circuit of Anti-bag snatching alarm Working principle of Anti-bag snatching alarm Here is a simple alarm circuit to thwart snatching of your valuables while travelling. The circuit kept in the bag or suitcase sounds a loud alarm, simulating a police horn, if someone attempts to snatch the bag or suit-case. This will draw the attention of other passengers and the burglar can be caught red handed. In the standby mode, the circuit is locked by a plug and socket arrangement (a mono plug with shorted leads plugged into the mono-jack socket of the unit). When the burglar tries to snatch the bag, the plug detaches from the unit’s socket to activate the alarm. The circuit is designed around op-amp IC CA3140 (IC1), which is configured as a comparator. The non-inverting input (pin 3) of IC1 is kept at half the supply voltage (around 4.5V) by the potential divider comprising resistors R2 and R3 of 100 kilo-ohms each. The inverting input (pin 2) of IC1 is kept low through the shorted plug at the socket. As a result, the voltage at the non-inverting input is higher than at the inverting input and the output of IC1 is high. Working principle of Anti-bag snatching alarm The output from pin 6 of IC1 is fed to trigger pin 2 of IC NE555 (IC2) via coupling capacitor C1 (0.0047 μF). IC2 is configured as a monostable. Its trigger pin 2 is held high by resistor R4 (10 kilo-ohms). Normally, the output of IC2 remains low and the alarm is off. Resistor R6, along with capacitor C3 connected to reset pin 4 of IC2, prevents any false triggering. Resistor R5 (10 mega-ohms), preset VR (10 mega- ohms) and capacitor C2 (4.7 μF, 16V) are timing components. With these values, the output at pin 3 of IC2 is about one minute, which can be increased by increasing either the value of capacitor C2 or preset VR. When there is an attempt at snatching, the plug connected to the circuit detaches. At that moment, the voltage at the inverting input of IC1 exceeds the voltage at the non-inverting input and sub-sequently its output goes low. This sends a low pulse to trigger pin 2 of IC2 to make its output pin 3 high. Consequently, the alarm circuit built around IC UM3561 (IC3) gets the supply voltage at its pin 5. IC UM3561 is a complex ROM with an inbuilt oscillator. Resistor R8 forms the oscillator component. Working principle of Anti-bag snatching alarm Its output is fed to the base of single-stage transistor amplifier BD139 (T1) through resistor R9 (1 kilo-ohm). The alarm tone generated from IC3 is amplified by transistor T1. A loudspeaker is connected to the collector of T1 to produce the alarm. The alarm can be put off if the plug is inserted into the socket again. Transistor T1 requires a heat-sink. Resistor R7 (330 ohms) limits the current to IC3 and zener diode ZD1 limits the supply voltage to IC3 to a safe level of 3.3 volts. Resistor R9 limits the cur- rent to the base of T1. The circuit can be easily constructed on a vero board or generalpurpose PCB. Using a small case for housing the circuit and 9V battery. The speaker should be small so as to make the gadget handy. Connecting a thin plastic wire to the plug and securing it in hand or tie up somewhere else so that when the bag is pulled, the plug detaches from the socket easily. Circuit Instrument Description Operational Amplifier: The IC requires very low input current as low as 10pA to change the output status, high or low. The IC has very fast response and high speed of performance. The output stage of the IC uses bipolar transistors and includes built in protection against damage from load terminal short circuiting to either supply rails or to ground. Circuit Instrument Description Timer IC (NE555): 555 is a very commonly used IC for generating accurate timing pulses. It is an 8pin timer IC and has mainly two modes of operation: monostable and astable. In monostable mode time delay of the pulses can be precisely controlled by an external resistor and a capacitor whereas in astable mode the frequency & duty cycle are controlled by two external resistors and a capacitor. 555 is very commonly used for generating time delay and pulses. Circuit Instrument Description Complex ROM with an inbuilt oscillator (UM3561): UM 3561 is an excellent Siren generator IC widely used in Toy applications and Surveillance systems to generate different tones. It a ROM (Read Only Memory) IC which can be operated in 2 pen cells and it functions normally down to 2.4 volts. Using only a few components, it is very easy to construct a siren generator. The IC is designed to generate sirens like Police siren, Ambulance siren, Fire brigade siren and Machine gun sound. The IC has an inbuilt oscillator and tone selection pins. Only one external resistor and a soeaker driver transistor are sufficient to make a simple siren generator circuit. Circuit Instrument Description Transistor(BD139): BD139, BD140 are epitaxial planar transistors which are mounted in the SOT-32 plastic package. They are designed for audio amplifiers and drivers utilizing complementary or quasicomplementary circuits. Circuit Instrument Description Variable resistor: A potentiometer informally a pot, is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat. Circuit Instrument Description Zener Diode: A Zener diode is a diode which allows current to flow in the forward direction in the same manner as an ideal diode, but also permits it to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage. We use 3.3v Zener diode in this circuit. Circuit Instrument Description Speaker: A loudspeaker (or loud-speaker or speaker) is an electroacoustic transducer, a device which converts an electrical audio signal into a corresponding sound. List of components with price Name of component Quantity Price TK. Resistors(100K,10K, 10M,220K,1K,330)Ω 9 18 Capacitors(0.0047, 0.01,4.7)µF 4 20 Variable Resistor(1MΩ) 1 10 Op-amp IC(CA3140) 1 30 Timer IC(NE555) 1 15 Complex ROM with an inbuilt oscillator (UM3561) 1 30 Loud speaker(8Ω 0.5W) 1 45 Transistor(BD139) 1 15 Zener Diode (3.3v) 1 5 Battery (4.5V) 2 90 Mono jack with mono socket and switch and connecting wire 1 40 Total price = 318 TK. Advantages: Simple circuit design. Low cost. Bias voltage is low. Its easy to carry anywhere. Effectively applied in daily activities. Disadvantages: Its create noise because of police siren in the public place. Applications used in motor cycle to prevented theft. used in door of your Private room. used in laptop, if anyone open it, the alarm activated. used in suitcase, bag, purse etc. to prevented theft. Discussion of Anti-bag snatching alarm The design and construction of Anti-Bag snatching alarm was outlined in a block diagram and then circuits were designed and tested. Finally the circuits were arranged and connected properly and tested. In this project we use three IC(CA3140,NE555,UM3561). The circuit of the Ant-Bag Snatching Alarm is designed around the operational amplifier CA3140 (IC1)which is configured as a comparator. Normally, the non-inverting input is higher than inverting input and the output is high from the pin 6 and the output pin is fed to the trigger pin 2 of IC NE555. The cause of high output of IC1 the trigger pin 2 is high and as a result the IC 2 output pin 3 is low and the alarm is off. A resistor along with a capacitor is connected to reset pin 4 of IC2 in order to prevent false triggering. When there is a bag-snatching attempt, the plug connected to the circuit detaches. At that moment, the voltage at the inverting input of IC1 exceeds the voltage at the non-inverting input and subsequently its output goes low. Discussion of Anti-bag snatching alarm This sends a low pulse to trigger pin 2 of IC2 to make its output pin 3 high. Consequently, the alarm circuit built around IC UM3561 (IC3) gets the supply voltage at its pin 5. Its output is fed to the base of single-stage transistor amplifier BD139 (T1) that amplifies the generated alarm signal. A loudspeaker is connected to the collector of T1 to produce the alarm. The alarm can be put off if the plug is inserted into the socket again. It is a simple circuit and low costly. Its easy to carry anywhere with bag, suitcase and purse. Conclusion It can be used in a bag which prevents snatching and saves our life. When the bag is snatched then plug is detached and the alarm is activated immediately. Everyone can use this device by exchanging a small amount of price of just 320tk. Recommendation This anti-bag snatching alarm system is developed by using more high variable resistor, and loudspeaker for proper sound. It makes rechargeable by using circuit.