PROJECT ON HIGHWAY ALERT SIGNAL LAMP

1. INTRODUCTION

The lighting system of a motor vehicle consists of lighting and signalling devices mounted or integrated to the front, sides, rear, and in some cases the top of the vehicle. The purpose of this system is to provide illumination for the driver to operate the vehicle safely after dark, to increase the conspicuity of the vehicle, and to display information about the vehicle's presence, position, size, direction of travel, and driver's intentions regarding direction and speed of travel. Driving lamp" is a term deriving from the early days of night time driving, when it was relatively rare to encounter an opposing vehicle. Only on those occasions when opposing drivers passed each other would the dipped or "passing" beam be used. The full beam was therefore known as the driving beam. Turn signals are required to blink on and off, or "flash", at a steady rate of between 60 and 120 blinks per minute (Although some operate slower than this). International regulations require that all turn signals activated at the same time (i.e., all right signals or all left signals) flash in simultaneous phase with one another; North American regulations also require simultaneous operation, but permit side markers wired for side turn signal functionality to flash in opposite-phase. Worldwide regulations stipulate an audiovisual telltale when the turn signals are activated; this usually takes the form of one combined or separate left and right green indicator lights on the vehicle's instrument cluster, and a cyclical "tick-tock" noise generated electromechanically or electronically. It is also required that audio and/or visual warning be provided to the vehicle operator in the event of a turn signal's failure to light. This warning is usually provided by a much faster- or slower-than-normal flash rate, visible on the dashboard indicator, and audible via the faster tick-tock sound.

Turn signals are in almost every case activated by means of a horizontal lever (or "stalk") protruding from the side of the steering column, though some vehicles have the lever mounted instead to the dashboard. The outboard end of the stalk is pushed clockwise to activate the right turn signals, or anticlockwise for the left turn signals. This operation is intuitive; for any given steering manoeuvre, the stalk is pivoted in the same direction as the ateering wheel must be turned.

2. COMPONENTS USED

R1 = 8.2k

R2 = 4.7k

R3 = 10k

R4 = 100

R5 = 470

R6 = 22k                            

R7 = 33k

IC 555                                

Capacitor

Darlington Phototransistor (L14F1)

Transistor

LEDs

3. CIRCUIT DIAGRAM

 WORKING PRINCIPLE

This is the signal lamp for safe highway driving. The lamp automatically emits brilliant tricolour light when a vehicle approaches the rear side of your vehicle. It emits light for 30 seconds that turns off when the approaching vehicle overtakes. The ultra-bright blue, white and red LEDs of the signal lamp emit very bright light to alert the approaching vehicle’s driver even during the day, giving additional safety during night or when you need to stop your vehicle on side of the highway. The circuit saves considerable battery power.

The circuit is built around two timer ICs NE555(IC1& IC2). IC1 is designed as a standard monostable, while IC2 is designed as an astable. Darlington Phototransistor L14F1 (T1) is used as a photosensor to activate the monostable. The collector of Phototransistor T1 is connected to trigger pin 2 of IC1, which is normally kept high by resistor R1. When headlight from an approaching vehicle illuminates the phototransistor, it conducts to give a short pulse to IC1, and the output of IC1 goes high for a 4 period determined by resistor R2 and capacitor C1. The output of IC1 is fed to the base of transistor T2 via resistor R3. Transistor  T2 conducts to drive transistor T3 and its collector goes high to take reset pin 4 of IC2to high level. This activates astable IC2, which switches on and off  the LED chain alternately. The intermittent flashing of LEDs gives a beautiful tricolour flashing effect. 12 volt DC supply to the circuit, can be provided by your vehicle battery with proper polarity.

4. Components Used

555 IC

The 555 IC is available as an 8-pin metal can, an 8-pin mini DIP(dual in package) or a 14-pin DIP. This IC consists of 23 transistors, 2 diodes and 16 resistors.

Pin 1(Grounded Terminal):- All the voltages are measured w.r.t this terminal.

Pin 2(Trigger Terminal):- This pin is an inverting input to a comparator that is responsible for transition of flip-flop from set to reset.

Pin 3(Output Terminal):- Output of the timer is available at this pin.

Pin4(Reset Terminal):- To disable or reset the timer a negative pulse is applied to this pin due to which it is referred to reset terminal.

Pin 5(Control Voltage Terminal):- The function of this terminal is to control the threshold and trigger levels.

Pin 6(Threshold Terminal):- This is the non-inverting input terminal of comparator1, which compares the voltage applied to this terminal with a reference voltage of +2/3 Vcc.

Pin 7(Discharge Terminal):- This pin is connected internally to the collector of transistor and mostly a capacitor is connected between this terminal and ground.

Pin 8(Supply Terminal):- A supply voltage of +5V to +18V is applied to this terminal w.r.t ground.

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Fig. 2: IC555

Monostable mode

Monostable multivibrator often called a one shotmultivibrator is a pulse generating circuit in which the duration of this pulse is determined by the RC network connected externally to the 555 timer. In a stable or standby state, the output of the circuit is approximately zero or a logic-low level. When external trigger pulse is applied output is forced to go high (» V_CC). The time for which output remains high is determined by the external RC network connected to the timer. At the end of the timing interval, the output automatically reverts back to its logic-low stable state. The output stays low until trigger pulse is again applied. Then the cycle repeats. The monostable circuit has only one stable state (output low) hence the name monostable.

                            Fig.3: Circuit Diagram of Monostable Multivibrator

Waveform

Fig.4: Output Waveform of IC555 in Monostable Mode

Astable mode

The astable multivibrator generates a square wave, the period of which is determined by the circuit external to IC 555. The astable multivibrator does not require any external trigger to change the state of the  output. Hence the name free running oscillator. The time during which the output is either high or low is determined by the two resistors and a capacitor which are externally connected to the 555 timer. The figure shows the 555 timer connected as an astable multivibrator. Initially when the output is high capacitor C starts charging towards  V_cc through R_A and R_B.

Fig.5: Circuit Diagram of 555 timer in Astable Mode

Waveform

Fig.6: Output waveform of 555 timer in Astable Mode

Transistor

A transistor is a semiconductor device used to amplify and switch electronic signals. It is made of a solid piece of semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be much more than the controlling (input) power, the transistor provides amplification of a signal. Some transistors are packaged individually but many more are found embedded in integrated circuits.The transistor is the fundamental building block of modern electronic devices, and its presence is ubiquitous in modern electronic systems.

Fig.7: Transistor

 RESISTOR

A resistor is a two-terminal electronic component that produces a voltage across      its terminals that is proportional to the electric current through it in accordance with Ohm's law

     V = IR

Resistors are elements of electrical networks and electronic circuits and are ubiquitous in most electronic equipment.

Fig.8: Resistor

Capacitor

A capacitor is a passive electronic component consisting of a pair of conductors separated by a dielectric. When a voltage potential difference exists between the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force between the plates. An ideal capacitor is characterized by a single constant value, capacitance, which is measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them. In practice the dielectric between the plates passes a small amount of leakage current. The conductors and leads introduce an equivalent series resistance and the dielectric has an electric field strength limit resulting in a breakdown voltage.

They are widely used in electronic circuit to block the flow of direct current while allowing alternating current to pass, to filter out interferance, to smooth the output of power supplies, and for many other purposes. They are used in radio frequency equipment to select particular frequencies from a signal with many frequencies.

         

fig.9:Capacitor

LED

A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices, and are increasingly used for lighting. Introduced as a practical electronic component in 1962, early LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet and infrared wavelengths, with very high brightness.When a light-emitting diode is forward biased (switched on), electrons are able to recombine with holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the colour of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor. An LED is often small in area (less than 1 mm²), and integrated optical components may be used to shape its radiation pattern. LEDs present many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved robustness, smaller size, faster switching, and greater durability and reliability

Fig.10: LEDs

Battery

The battery cells create a voltage difference between the terminals of each   cell and hence to its combination in battery.

When an external circuit is connected to the battery, then the battery drives electrons through the circuit and electrical work is done. The battery has become a common power source for many household and industrial applications, and is now a multi-billion dollar industry.

Fig.11: Battery

PHOTOTRANSISTOR

Phototransistor is Like diodes, all transistorsare light-sensitive. Phototransistors are designed specifically to take advantage of this fact. The most-common variant is an NPN bipolar transistorwith an exposed baseregion. Here, light striking the basereplaces what would ordinarily be voltage applied to the base.  So, a phototransistor amplifies variations in the light striking it. Note that phototransistors may or may not have a baselead (if they do, the base lead allows you to bias the phototransistor’s light response. Here we use Darlington Phototransistor (L14F1) as a photosensor to activate the monostable IC1. The collector of phototransistor T1 is connected to trigger pin2 of IC1, which is normally kept high by resistor R1.When headlight from an approaching vehicle illuminates the phototransistor. It conduct to give a short pulse to IC1.

Fig.12: Darling-ton Phototransistor

CONCLUSION

In this project I have learned a lot about the SIGNAL LAMP scenario in the field of communication. This circuit is used for safe highway driving. This circuit inform the driver about the approaching vehicle. It also help the driver if the driver wants to stop for sometime on highway. It saves battery power. 


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