Introduction:
Table of Contents
Li-Fi is a wireless technology that uses visible light to transmit data, offering speeds of up to 10Gbit/s, over 250 times faster than superfast broadband. It is more efficient and cost-effective than traditional Wi-Fi, and holds promise for the f
Block Diagram:
Block diagram explanation:
Power supply unit
This section needs two voltages viz., +12 V & +5 V, as working voltages. Hence specially designed power supply is constructed to get regulated power supplies.
Microcontroller:
The Atmel AT89 series is an Intel 8051-compatible family of 8 bit microcontrollers (µCs) manufactured by the Atmel Corporation. Based on the Intel 8051 core, the AT89 series remains very popular as general purpose microcontrollers, due to their industry standard instruction set, and low unit cost. This allows a great amount of legacy code to be reused without modification in new applications. While considerably less powerful than the newer AT90 series of AVR RISC microcontrollers, new product development has continued with the AT89 series for the aforementioned advantages.
Preamplifier:
A preamplifier (preamp) is an electronic amplifier that prepares a small electrical signal for further amplification or processing. A preamplifier is often placed close to the sensor to reduce the effects of noise and interference. It is used to boost the signal strength to drive the cable to the main instrument without significantly degrading the signal-to-noise ratio(SNR)
Power amplifier:
An audio power amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 – 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers. It is the final electronic stage in a typical audio playback chain.
Li-Fi transmitter and receiver:
Li-Fi is implemented using white LED light bulbs at downlink transmitter. These devices are used for illumination only by applying a constant current. By fast and subtle variations of the current, optical output can be made to vary at extremely high speeds. This variation is used to carry high speed data.
Buffers
Buffers do not affect the logical state of a digital signal (i.e. a logic 1 input results in a logic 1 output whereas logic 0 input results in a logic 0 output). Buffers are normally used to provide extra current drive at the output but can also be used to regularize the logic present at an interface
Drivers
This section is used to drive the relay where the output is complement of input which is applied to the drive but current will be amplified
Relays
It is a electromagnetic device which is used to drive the load connected across the relay and the o/p of relay can be connected to controller or load for further processing.
Methodology:
In the process of data communication through the visible light on the transmitter side Keypad is used as the input signal. The microcontroller receives the signal from the keypad and generates two outputs and gives that signal to the DTMF Encoder. The encoder will generate one tone and one frequency for every pressed key. That frequency is amplified by the amplifier circuits and fed into the power LED. At the receiver side light dependant resister will receive the light signal and correspondingly generate an electrical signal proportional to it. This electrical signal is processed by a demodulator circuit (DTMF Decoder), and the output of decoder is then fed to a microcontroller and the microcontroller activates the corresponding load for the pressed key.
Advantages:
- Harmless for the human body
- Data transmission by sockets of existing light fixtures
- Alleviation of problems associated with the radio frequency (RF) communication system
- Less energy consumption.
- Increased security.
- Compact integration of sensors through small dimensions
- Huge number of channels available without interfering with other sources.
- Simple electronics as drive for the LED’s.
- No influence to other sensitive equipment through radio waves.
Disadvantages
1. To transmit the data it should be in the line of sight.
Applications
- Smart lighting
- Mobile connectivity
- Hazardous environments
- Defense & security
- Hospitals & healthcare
- Wi-Fi spectrum relief
- Underwater communications
- Location based services
