Intelligent traffic light system using Light-Fidelity (Visible Light Communication)
Volumn 3

Intelligent traffic light system using Light-Fidelity (Visible Light Communication)

Kalpak Chandekar, Sweta Gautam, Tanmaya Deb, Sweety Kumari, Dr. V. K. Taksande

Electronics and Telecommunication Department

Priyadarshini College of Engineering Nagpur, India.

Email address-,

Contact No. +91-9595719420


In Li-Fi (light fidelity) we transmit the data in parallel bit stream with high speed. Li-Fi is a VLC, that is, visible light communication. Li-Fi is now a part of the Visible Light Communications (VLC) PAN IEEE 802.15.7 standard.

Road accidents cause loss of material and most importantly human lives and are becoming severe even with the deployment of many intelligent communication devices on board vehicle and alongside the road. Our roads are not ambulance friendly most often. It is difficult but we are managing.

Most ‘BROUGHT DEAD’ and ‘DIED ON ROUTE’ cases happen when there is a time lag in shifting the patients from one place to another because of traffic jams, mostly in urban cities. To deal with these problems we tried to come up with a solution by developing a system which uses the VLC broadcast system using LED-based traffic lights.

Keywords—Li-fi; visible light communication.

I. Introduction

Visible Light is the light visible to the human eye and is mainly responsible for the sense of sight. It is usually defined to be having wavelength in the range of 400-700 nm, between infrared and ultra-violet. Frequency range of visible light roughly 430-750 THz (terahertz). Like all types of light, visible light is emitted and absorbed in tiny packets called “photons” and exhibit properties of both waves and particles. The speed of light in vacuum is calculated to be accurately 299,792,458 m/sec. Li-Fi is basically a light based communication technology that delivers high speed data communication, and is useful in mobile communication. Li-Fi is based on visible light spectrum which provides spectrum which is calculated to be more than 10,000 times to radio waves to deliver the desired data. In this paper, we study the use of VLC in Intelligent Traffic Light System`, thus understanding the limitations and how Li-Fi will be useful in near future.


LED is connected to the transmitter and photodetector to the receiver. Photo detector in the receiver registers a binary ‘1’ for ON else it registers ‘0’ for OFF. The LED’s can be switched ON and OFF very rapidly which gives good opportunities for transmitting the desired data. LED is light emitting device and it can be switched ON and OFF very rapidly in a way such that it is totally unperceivable to the human eyes. When the system is turned on then it will give the possibility to send independent communication signal from each individual LED in the array. This will be helpful in transmitting important data to more than one vehicle at a single instant of time. The receiver in vehicles will intercept the transmitted data with the help of photodetector and display it on the LCD screen which will provide for assistance to the driver to take necessary action.

III. Transmitter Section

The transmitter is a main component in the process. It has many components. 

A. Basic Circuit Diagram

B. Light Emitting Diodes

LED’S are semiconductor electronic device. LED’s can simultaneously perform many task such as deliver data, display information and provide lightning. It is a next stage to research visible light to transmit data means that we take new generation of energy saving light bulbs which are made up of LED’s and use same illumination end for high speed data transmission. The LED is usually made from gallium nitrate, a manmade semiconductor material. It’s very good characteristics that its intensity can be controlled at a very high speed that means it can be switched ON and OFF at a very high speed which is the basic fundamental property used in LIFI.   

C. Crystal Oscillator

The crystal oscillator used in this transmitter works at a frequency of 11.05MHz. It provides the circuit with a constant and stable frequency so as to maintain a standard clock pulse in the circuit.

D. Microcontroller ATMEL 89c51

The AT89c51 is a high-performance CMOS 8-bit microcomputer, which uses low-power, with 8K bytes of Flash programmable and erasable read only memory. The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard 80C51 and 80C52 instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89c51 is a powerful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications. The AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, five vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset. These are the features of 89C51.

  • Compatible with all MCS-51™ products
  • 8K Bytes of In-System Reprogrammable Flash Memory
  • Endurance: 1,000 Write/Erase Cycles
  • Fully Static Operation: 0 Hz to 24 MHz
  • Three-level Program Memory Lock
  • 256 x 8-bit Internal RAM
  • 32 Programmable I/O Lines
  • Three 16-bit Timer/Counters

IV. Receiver section

The signal is received through photo detector of receiver circuit and processing of the signal is done in microcontroller of the receiver section. Receiver ignores the incoming constant intensity of light because receiver is interested only in certain changes or modulated intensity at very high speed in the form of 0’s and 1’s. Other important component of the receiver is the LCD screen.

A. Basic Circuit Diagram

B. Photodetector

Photo detectors are devices used for the detection of light in most cases of optical powers. They are primarily used as an optical receiver for converting light into electricity. The photoelectric effect is the principle that applies to photo detectors, which is the effect on a circuit due to light. A photo detector operates by converting light signals that hit the junction into a voltage or current. The junction uses a radiance window with an anti-reflect coating to absorb the light photons. In this project the photo detector absorbs light from the LEDs and picks up the signal and that is converted back into a data stream and sent to the microcontroller for further processing.

C. Liquid Crystal Display

LCD is the technology used for displays. It is basically an electronic visual display which uses the characteristics, specifically the light modulating properties of liquid crystal as they cannot emit light directly. It is capable of displaying fixed and flat images. The LCD used is 2×16 grids in dimension. It displays the data from the microcontroller into readable form by parallel communication. 

D. Voltage Regulator LM7805

The LM7805 series of three terminal positive regulators are available in the TO-220/D-PAK package and with several fixed output voltages, making them useful in a wide range of applications. Each type employs thermal shut down, internal current limiting, and safe operating area protection, making it essentially indestructible. If adequate heat sinking is provided to it, LM7805 can deliver over 1A output current. Although designed primarily as fixed voltage regulators, these devices can be used with external components to obtain adjustable voltages and currents. These are the features of LM805.

  • Output Current up to 1A
  • Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V
  • Thermal Overload Protection
  • Short Circuit Protection
  • Output Transistor Safe Operating Area Protection

Voltage regulator basically limits the voltage that passes through it. Each regulator has a voltage rating. For example, the 7805 IC (these regulators are often considered to be ICs) is a 5-volt voltage regulator. What that means is that no matter how many volts you put into it, it will output only 5 volts. This means that we can connect a 9-volt battery, a 12-volt power supply, or virtually anything else that’s over 5 volts, and have the 7805 provide a supply of 5 volts out. There are also 7812 (12-volt) and 7815 (15-volt) three-pin regulators which are in common use.


We wish to express our sincere and deep sense of gratitude to our Guide Dr. Mr. V. K. Taksande & Co-guide O.G.Hastak, who continuously supervised our work with utmost care. They have always guided us in our endeavor to present our project on “INTELLIGENT TRAFFIC LIGHT SYSTEM USING LI-FI (VLC)”. It’s a great pleasure to express our deep sense of gratitude and the whole hearted thanks to our principal Dr. M. P. SINGH, Priyadarshini College of Engineering, Nagpur.

We offer special thanks to our Head of the Department Dr. (Mrs.) S. W. Varade, for giving us the opportunity to undertake this project. We offer hearty gratitude to, Lab assistants of ETC Department, Priyadarshini College of Engineering, for their valuable support during the execution of the project work.

Lastly, we express our deep sense of gratitude to all teaching and non-teaching staff of the College and all our friends, family members, who directly and indirectly helped us to complete our project successfully and to bring it into reality.


  1. “Visible-light communication: Tripping the light fantastic:  A fast and cheap optical version of Wi-Fi is coming”. The Economist. 28 January 2012.  Retrieved 22 October 2013.
  2. Haas, Harald (July 2011). “Wireless data from every        light bulb”. TED Global. Edinburgh, Scotland.
  3.  Iain Thomson (18 October 2013). “Forget Wi-Fi, boffins’        get 150Mbps Li-Fi connection from a light bulb: Many hands make light work”. The Register. Retrieved 22Oct13.
  4. Wi-Fi Alliance: organizationǁ Retrieved august 23, 2011.
  5. Hassan Yagoobi, Scalable OFDMA Physical Layer in   IEEE 802.16 Wireless MAN, Intel Technology Journal, Vol  08, August 2004.
  6. W. Xiao and R. Ratasuk- Analysis of Hybrid ARQ with Link Adaptation, Proceedings of the Annual Allerton Conference on Communications.

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