CFL & LED lamps Compact Fluorescent Lamp (CFL) • compact fluorescent light, energy-saving light, and compact fluorescent tube. • The CFL was initially designed to replace the incandescent lamp in terms of its compactness as well as energy efficiency. • The basic construction of a CFL consists a tube which is curved/spiraled to fit into the space of an incandescent bulb, and a compact electronic ballast in the base of the lamp. How Compact Fluorescent Lamp (CFL) works – Working Principle • A CFL uses vacuum pipe which is principle wise same to the strip lamps (commonly known as Tube light) . • Tube has two electrodes on both ends which is treated with Barium. • Cathode is having a temperature of about 900º C and generates a beam of electrons which is further accelerated by potential difference between electrodes. • These accelerated electrons strike Mercury and Argon atoms which in turn results in the arise of a low temperature plasma • This process initiates the radiation of Mercury in Ultra violet form. • Tube’s inside face contains ‘Luminophore’ whose function is to convert Ultra violet light into visible light. • This tube is fed with AC power supply which facilitate the changing functionality of Anode and Cathode. • The CFL also consists a switched mode converter. It functions on a very high frequency and acts as a replacement of ballast (choke) and starter assembly. Circuit Explanation of CFL • The CFL PCB is quite compact and fits in the holder base. • Though being compact, it efficiently performs the requirements as a choke. • Key components of PCB of CFL The PCB of a CFL contains the following key components : • • • • • Bridge rectifier made up of diode 1N-4007 Suppressor for suppressing interference Filter capacitor Fuse point Supply point Phase wise Circuit Explanation of CFL • The working of a CFL can be divided into two broad phases: – • Starting Phase • Normal Phase • Starting Phase • The starter segment comprise of a Diac, C2, D1 and R6. The components D3, R3, D2 and R1 work as a protection circuit and the rest as normal operation circuit. • D refers for diode • R refers for Resistor • C refers for Capacitor, and • Q stands for Transistor • The Diac, C2 and R2 send a voltage pulse to Q2 Transistor’s base which causes it to get its threshold value and it starts operating. • As soon as the operation starts, the D1 diode blocks the whole section. • Capacitor C2 is also discharged (after charged to its full value) each time the transistor Q2 operates. • Therefore after its first start, There is not enough energy left for reopening of Diac. • Further, the transistors are excited with the help of TR1 transformer. • As the voltage is raised from resonant circuit (L1, TR1, C3 and C6), the tube lights up as soon as resonant voltage is specified by capacitor C3 (which feeds Filaments). • At this moment the voltage C3 is over 600V. • Normal Phase • Just after the ionisation of gas present in the vacuum-pipe, the practical shorting of capacitor C3 is carried out. • This results in stepping down of the voltage. After that C6 starts driving the changer. A very small voltage is generated by this change, yet it is sufficient to run the lamp in ‘ON’ condition. • Under regular running condition, if the transistor comes in OPEN state, The current being fed to TR1 keeps increasing till the core of transformer saturates, and thus the feed to base drops down resulting it to close the transistor. • Immediately after this process, the second transistor is excited by reverse winding of TR1 and so the process goes on. • • • • • • • • • • • Advantages of Compact Fluorescent Lamp (CFL) The advantages of CFL are as follows: – It is energy efficiency It has a higher life span ( nearly five to fifteen times) compared to the old filament bulbs. It has lesser power rating (almost 80 percent) compared to the old filament bulbs. It is low life cycle cost. Though, it has a higher purchase price than an incandescent lamp, it can save over five times its purchase price in electricity costs over the lamp’s lifetime. Disadvantages of Compact Fluorescent Lamp (CFL) It takes more time to start The initial Purchase cost is high. It does not comes in dark shades too. Like all other fluorescent lamps, CFLs contain mercury, which complicates their disposal. How is performance affected by ambient temperature? • Performance characteristics of compact fluorescent lamps will be affected by lamp base position and by operation in cold or hot environments. • Temperature impacts both short-term and long-term performance. In the short-term, temperature impacts CFL light output, electric power, and luminous efficacy, with most lamps operating at their peak in an ambient temperature of about 77°F (25°C). • Over long periods of time, elevated temperatures may shorten ballast life and consequently reduce lamp life in self-ballasted CFLs. Short-term thermal effects Operating fluorescent lamps in cold or hot environments will lead to reduced light output, reduced power, and reduced efficacy, as shown in Figure Figure 9. Impact of ambient temperature on power, light output, and efficacy of many fluorescent lamps • Some manufacturers of CFLs report information about light output at a range of temperatures • If this information is not available, users can generalize from other curves showing fluorescent output for minimum bulb wall temperature or ambient temperature, such as Figure As shown in Figure reduction in light output can be minimized with the use of a mercury amalgam Use of mercury amalgam with CFLs is often not reported in lamp catalog information. However, users can request this information from the lamp manufacturer. Figure 10. Impact of ambient temperature on light output of amalgam and nonamalgam fluorescent lamps LED lamp • An LED lamp or LED light bulb is an electric light for use in light fixtures that produces light using one or more light-emitting diodes (LEDs). • LED lamps have a lifespan many times longer than equivalent incandescent lamps, and are significantly more efficient than most fluorescent lamps, with some LED chips able to emit up to 303 lumens per watt (as claimed by Cree and some other LED manufacturers). • However, LED lamps require an electronic LED driver circuit when operated from mains power lines, and losses from this circuit means that the efficiency of the lamp is lower than the efficiency of the LED chips it uses. • The most efficient commercially available LED lamps have efficiencies of 200 lumens per watt (Lm/W). • The LED lamp market is projected to grow by more than twelve-fold over the next decade, from $2 billion in the beginning of 2014 to $25 billion in 2023, a compound annual growth rate (CAGR) of 25%. • As of 2016, many LEDs use only about 10% of the energy an incandescent lamp requires. • Similar to incandescent lamps (and unlike most fluorescent lamps), LEDs come to full brightness immediately with no warm-up delay. • Frequent switching on and off does not reduce life expectancy as with fluorescent lighting • Light output decreases gradually over the lifetime of the LED (see Efficiency droop section). • Some LED lamps are made to be a directly compatible drop-in replacement for incandescent or fluorescent lamps. • LED lamp packaging may show the light output in lumens, the power consumption in watts, the color temperature in Kelvin or a colour description such as "warm white", "cool white" or "daylight", the operating temperature range, and sometimes the equivalent wattage of an incandescent lamp delivering the same output in lumens. • The directional emission characteristics of LEDs affect the design of lamps. • While a single power LED may produce as much light output as an incandescent lamp using several times as much power, in most general lighting applications multiple LEDs are used. • This can form a lamp with improved cost, light distribution, heat dissipation and possibly also color-rendering characteristics. • LEDs run on direct current (DC), whereas mains current is alternating current (AC) and usually at much higher voltage than the LED can accept. • LED lamps can contain a circuit for converting the mains AC into DC at the correct voltage. • These circuits contain rectifiers, capacitors, and may have other active electronic components, which may also permit the lamp to be dimmed. • In an LED filament lamp, the driving circuit is simplified because many LED junctions in series have approximately the same operating voltage as the AC supply. • LEDs require a power supply system (driver) to interface them with the electric network. Generally the current waveform contains some amount of distortion, depending on the luminaries’ technology.[11] • LED lamps are often made with arrays of surface mount LED modules (SMD modules) that replace incandescent or compact fluorescent lamps, mostly replacing incandescent lamps rated from 5 to 200 watts. • A significant difference from other light sources is that the light is more directional, i.e., emitted as a narrower beam What is Li-Fi Technology – How it Works, Applications & Advantages • Li-Fi is a new way of wirelesscommunication which uses LED lights to transmit data wirelessly. • The data flow speed of this wireless data communication technology is quite high and has low cost installation. It is well accepted that transmission of data is one of the most important day to day activities in today’s fast changing world. Some problems that is normally faced are: • Slow connection to the Internet when multiple devices are connected • Unavailability of fixed bandwidth due to overcrowding does not allow high data transfer rates. • This technology can be a solution to all these problems. Researches are going on to develop this technology on a broad scope. Fig. 1 – Introduction to Li-Fi Technology What is Li-Fi Technology • The term Li-Fi (Light and Fidelity) refers to Visible Light Communication (VLC) technology. This technology uses a part of the electromagnetic spectrum that is still not utilized generally i.e. the Visible Spectrum. • In simple terms, LiFi is a light-based Wi-Fi. This technology has a much broader spectrum for transmission compared to conventional methods of wireless communication which uses radio waves. • The basic ideology of this technology is transference of data using LED light of varying intensities. • It uses transceivers fitted with LED lamps that can transmit and receive information. • This results in adding new and unutilized bandwidth of visible light and may offer additional frequency band than those bands which are available for RF communication. Fig. 2 – Uses of Electromagnetic Spectrum • Since LiFi uses the visible spectrum, concerns of adverse effects of electromagnetic waves (associated with Wi-Fi technology) gets alleviated. • Security concerns are also reduced as data or information on the Internet cannot be accessed in the absence of light. • How Does a Li-Fi Work • Li-Fi is a Visible Light Communications (VLC) system and such a system has two qualifying components: • One device with a Photo-diode able to receive light signals. • A light source coupled with a Signal Processing Unit. • The VLC system signals work by switching bulbs on and off within nanoseconds such that human eyes are unable to notice it. • High brightness white LED acts as a light source i.e. as transmission source. • A silicon photo-diode with good response to visible light is the receiving element. Fig. 3 – How Does the Li-Fi Technology Work • LEDs are switched on and off to generate digital strings of combination of 1s and 0s. • To generate a new data stream, data is encoded in the light by changing the flickering rate of the LED, which is used as the source. • The LED output appears constant to the human eye by the fast flickering rate of the LED. • VLC data rate is increased by parallel data transmission using an array of LEDs where each LED transmits a different data stream. • Applications of Li-Fi Technology • This technology has a wide range of applications such as: • Public Internet access using existing LED lighting. • Auto-piloted cars that communicate through their LED based headlights. • Connecting with specialists across the globe from the operation theater. • Since it uses just the light, it can be used safely in locations or areas where the presence of radio waves raises concerns of security. • Advantages of Li-Fi technology are: • Efficiency: Efficient use of energy consumption due to the use of LED illumination which are already in use for lighting purpose. Hence the transmission of data will require negligible additional power/ energy. • High speed: The technology uses bandwidth that is not is use currently. Hence, low interference, wider bandwidths and highintensity output are its key data features. • Availability: As the light source is available everywhere, availability is not an issue. Hence, wherever there is a light source, there will be Internet. • Cost Efficient: This technology requires few components for its working. The technology also uses negligible additional power for data transmission. Overall, utilization of this technology becomes cost efficient. • Security: within a confined area. This internet cannot be intercepted and misused outsideAs light cannot pass through opaque structures, LiFi internet is available only to those the area under operation. • Futuristic: This technology has a great scope in future due to the extensive growth in the use of LEDs. Overall, it is considered a sustainable model for Internet access as it incurs lower cost and offers higher efficiency. • Limitations of Li-Fi • Some of the major limitations of Li-Fi are: • Access of internet is limited by the presence of a light source. • Data transmission speed can get lowered because of interference of natural light (sunlight) and normal electric light. • Since light cannot pass through opaque objects, obstacles on pathways can affect data transmission. • It has a much shorter range than Wi-Fi. • Not yet developed for mass scale adoption. Fig. 5 – Strength and Weakness of LiFi Technology What is the difference between Wi-Fi and Li-Fi Technology Wi-Fi offers highest speed access to internet among the current technology. However, if we compare Li-Fi with Wi-Fi, we find the following key differences: Li-Fi • Spectrum Used Wi-Fi Visual Light Radio Frequency Range Depends on light intensity, can be lower than Wi-Fi Less than 200 meters Cost High installation cost, low regular usage cost Low cost Security High Less (compared to Li-Fi) Data transfer speed Higher (compared to Wi-Fi, can be up to 100 times faster) High Availability Yet to be available for commercial use Widely available Due to the speed and security offered by Li-Fi technology compared to Wi-Fi, Li-Fi is here to stay and likely to be used widely.
