ANTI-THEFT ALARM FOR BIKES
INTRODUCTION
Anti-Theft Alarm for Bikes is a kit which is used to protect the bike from unauthorized person. It is based on the very basic principle of Infrared Remote Control. According to this principle when transmitter and receiver section are aligned to each other, then the horn of bike become active and thus protects the bike from being theft.
THEORY
Transmitter section consist of a power supply, an oscillator and an output stage. Receiver section comprises power supply, an IR Detector Module, time delay circuit with noise filter, bistable flip-flop and an output section.
In the Tx section, IC1(555) is wired as an astable multivibrator. When switch S1 is pressed, the circuit get energized. Output of IC1 is a square wave. The IR LED connected at its output transmits IR beam.
The Rx uses an IR sensor module for sensing the IR signals from Tx section. When switch S1 on, the Tx is pressed, the IR LED radiate IR beams, the IR signals from the Tx section is sensed by the sensor and its output at Pin 2 goes low. This in turn switches on transistor T1. Consequently, capacitor C8 starts charging through resistor R5.
When voltage across capacitor C8 reaches about 3.5V, IC2 receives a clock pulse at Pin 14 and its output at Pin 2 goes high. This results in the forward biasing of transistor T2, which on conduction energizes relay RL1 connected at its collector. The output of IC2 is also used for lighting LED1, indicating presence of signal.
When no signal is available output of the sensor module goes high and transistor T1 is switched off. Now capacitor C8 starts discharging through resistor R6 and voltage across it gradually decrease to zero.
If an unwanted signal with the same frequency as that t of transmitter happens to arrive at sensor, its output will go low and IC2 would have change its output state. But fortunately, the noise signal is of very short duration and hence they cannot interference with the circuit. Because, with in this short time period, capacitor C8 cannot charge to a voltage equal to VH value through resistor R5, and so these noise pulse do not have any effect on the circuit.
Capacitor C10 and resistor R7 connected to the reset Pin 15 of IC2, prevent it from switching of the relay when the power supply fails and then resumes. Voltage regulator IC3 provides 5V regulated voltage for the circuit.
LIST OF COMPONENTS
SEMICONDUCTORS
IC1 555 TIMER
IC2 4017 DECADE COUNTER
IC3 7805 VOLTAGE REGULATOR
TRANSISTOR BC 557, BC 148
DIODE 1N 4001 RECTIFIER DIODE,
1N 4148 SWITCHING DIODE
LED1, LED 2 IR LED, INDICATOR
ESISTORS
R1, R5 4.7KΩ
R2, R4, R8 10KΩ
R3 100Ω
R6 470KΩ
R7 220KΩ
R9 1KΩ
VR1 10KΩ
CAPACITOR
C1 10 µF, 16V
C2 0.001µF
C3 0.01µF
C4 1000µF, 25V
C5,C9 0.1µF
C6 100µF, 16V
C7 47µF, 16V
C8 1µF, 16V
C10 2.2µF, 16V
MISCELLANEOUS
S1 PUSH TO ON SWTCH
RL1 12V, 200Ω RELAY
B1 9V BATTERY
INFRA RED SENSOR MODULE
ASTABLE MODE OF OPERATION
The other basic operational mode of the 555 is as and astable multivibrator. An astable multivibrator is simply an oscillator. The astable multivibrator generates a continuous stream of rectangular off-on pulse that switch between two voltage
levels. The frequency of the pulses and their duty cycle are dependent upon the
RC network is the common power rail. For the rest everything remains the same as the single version, 8-pin 555.
RELAYS
A relay is an electrical switch that opens and closes under control of another electrical circuit. In the original form, the switch is operated by an electromagnet to open or close one or many sets of contacts. It was invented by Joseph Henry in 1835. Because a relay is able to control an output circuit of higher power than the input circuit, it can be considered, in a broad sense, to be a form of electrical amplifier.
Operation
When a current flows through the coil, the resulting magnetic field attracts an armature that is mechanically linked to a moving contact. The movement either makes or breaks a connection with a fixed contact. When the current to the coil is switched off, the armature is returned by a force that is half as strong as the magnetic force to its relaxed position. Usually this is a spring, but gravity is also used commonly in industrial motor starters. Relays are manufactured to operate quickly. In a low voltage application, this is to reduce noise. In a high voltage or high current application, this is to reduce arcing.
If the coil is energized with DC, a diode is frequently installed across the coil, to dissipate the energy from the collapsing magnetic field at deactivation, which would otherwise generate a spike of voltage and might cause damage to circuit components. If the coil is designed to be energized with AC, a small copper ring can be crimped to the end of the solenoid. This "shading ring" creates a small out-of-phase current, which increases the minimum pull on the armature during the AC cycle. [1]
The contacts can be either Normally Open (NO), Normally Closed (NC), or change-over contacts.
• Normally-open contacts connect the circuit when the relay is activated; the circuit is disconnected when the relay is inactive. It is also called Form A contact or "make" contact. Form A contact is ideal for applications that require to switch a high-current power source from a remote device.
• Normally-closed contacts disconnect the circuit when the relay is activated; the circuit is connected when the relay is inactive. It is also called Form B contact or "break" contact. Form B contact is ideal for applications that require the circuit to remain closed until the relay is activated.
• Change-over contacts control two circuits: one normally-open contact and one normally-closed contact with a common terminal. It is also called Form C contact or "transfer" contact.
By analogy with the functions of the original electromagnetic device, a solid-state relay is made with a thyristor or other solid-state switching device. To achieve electrical isolation, a light-emitting diode (LED) is used with a photo transistor.
Types of relay
A solid state relay, which has no moving parts
• latching relays are available that have two relaxed states (bistable). These are also called 'keep' relays. When the current is switched off, the relay remains in its last state.This type of relay has the advantage that it consumes power only for an instant, while it is being switched, and it retains its last setting across a power outage.
• A reed relay has a set of, usually normally open, contacts inside a vacuum or inert gas filled glass tube. This protects the contacts against atmospheric corrosion
• A mercury wetted relay is a form of reed relay in which the contacts are wetted with mercury. Mercury wetted relays are position-sensitive and must be mounted vertically to work properly. Because of the toxicity and expense of liquid mercury, these relays are rarely specified for new equipment
• A machine tool relay is a type standardized for industrial control of machine tools, transfer machines.
• A contactor is a very heavy-duty relay used for switching electric motors and lighting loads. With high current, the contacts are made with pure silver.
• A Buchholz relay is a safety device sensing the accumulation of gas in large oil-filled transformers, which will alarm on slow accumulation of gas or shut down the transformer if gas is produced rapidly in the transformer oil.
• A forced-guided contacts relay has relay contacts that are mechanically linked together, so that when the relay coil is energized or de-energized, all of the linked contacts move together. If one set of contacts in the relay becomes immobilized, no other contact of the same relay will be able to move. The function of forced-guided contacts is to enable the safety circuit to check the status of the relay.
• A solid-state relay (SSR) is a solid state electronic component that provides a similar function to an electromechanical relay but does not have any moving components, increasing long-term reliability.
4017 DECADE COUNTER

The 4017 IC is a 16-pin CMOS decade counter from the 4000 series. It takes clock pulses from the clock input, and makes one of the ten outputs come on in sequence each time a clock pulse arrives.

Pin number Name Purpose
1 6 The 6th sequential output
2 2 The 2nd sequential output
3 1 The 1st sequential output
4 3 The 3rd sequential output
5 7 The 7th sequential output
6 8 The 8th sequential output
7 4 The 4th sequential output
8 0V, VDD The connection to the 0V rail
9 9 The 9th sequential output
10 5 The 5th sequential output
11 10 The 10th sequential output
12 CO Carry Out output - outputs high on counts 0 to 4, outputs low on counts 5 to 9 (thus a transition from low to high occurs when counting from 9 back to 0)
13 LE Latch enable - latches on the current output when high (i.e. the chip counts when LE is low)
14 CLK Clock in
15 RST Reset - sets output 1 high and outputs 2 through 10 low, when taken high
16 +9V, VCC The connection to the +VCC rail (voltage between +3V and +15V)
Counters in digital circuits are used for scaling and counting the number of incoming pulses. We have already seen that a D-type or a J-K flip-flop divides the input signal by two. The simplest dividing circuit is therefore, a binary counter, consisting of a number of flip-flops connected in tandem, so that the output of one flip-flop toggles the next one such an arrangement is called a ‘ripple counter’; and can divide an incoming signal by any multiple of two, depending on the number of flip-flops used.
If the output state of each flip-flop is displayed, say by LED’s, the number of pulses applied to the counter can be read any time as a binary number. The first flip-flop will show the Least Significant Bit(LSB), while the last flip-flop will show the Most Significant Bit(MSB). The binary number can be converted and displayed as a decimal number by Decoder/Display Driver circuits.