60-65_Optica_139_Ing 12/11/07 15:18 Page 60 Innovative traffic light: a special lens distributes and emits the luminous effect from the LEDs 60-65_Optica_139_Ing 12/11/07 15:18 Page 61 > TECHNOLOGY OPTICS The LED revolution Researchers from São Carlos develop equipment with light emitting diodes YURI VASCONCELOS | PHOTOS EDUARDO CESAR Published in September 2007 A new concept in traffic lights, with an innovative design, which is lighter and more compact and which, in place of traditional incandescent bulbs, use high-brightness light- emitting diodes as their source of light, the so-called LEDs, has been created by researchers at the São Car- los Research Center in Optics and Photonics (Cepof) of the University of São Paulo (USP). The new equipment is flat, is less than 2 centimeters thick and is easily in- stalled. Other advantages lie in its low power consump- tion (15% less than traditional traffic lights) and in the fact that it keeps working even if there is a power cut in the region. This happens because it is attached to a set of compact batteries that keep it functioning for up to one and a half hours if there is a blackout. PESQUISA FAPESP ■ SPECIAL ISSUE NOV 2006/SEP 2007 ■ 61 60-65_Optica_139_Ing 12/11/07 15:18 Page 62 very much more efficient that in com- mon lamps, with up to 80% of the elec- tricity used being converted into lumi- nous energy. This represents an inver- sion in the efficiency of light produc- tion, because the rate of conversion of incandescent lamps is only 20%”,ex- plains Bagnato.“LEDs stopped being simply those small, normally red or green indicator lights on the panels of sound systems and other electronic equipment a long time ago to become an effective lighting source.” An advantageous substitution – An- other application in the road signaling sector that was developed at Cepof in Retrofit substitutes São Carlos, one of 11 Innovation and traditional traffic light Diffusion Research Centers (Cepid) fi- lamps and reduces nanced by FAPESP,is a system called maintenance costs ‘retrofit’,which uses six or seven LEDs and was created to substitute just the incandescent lamps used in traditional traffic lights. Unlike the ‘blackout’ traf- fic light, in which the LEDs are an inte- gral part of the reflective lenses, the “The technology is cheaper than ate in the traffic signal sector to nego- ‘retrofit’ has a shape that is similar to conventional technology, it is eco- tiate passing on the technology. that an ordinary lamp and a screw sock- nomical in terms of energy consump- The ‘blackout’ traffic light is just one et, which allows it to easily substitute tion and has low maintenance costs”, of the applications produced by the conventional lights. The technology was says the professor from USP’s Physics team led by Bagnato that is based on passed on to ‘Meng Engenharia’,in São Institute in São Carlos, Vanderlei Sal- LED technology. The group, compris- Paulo and has been on sale since vador Bagnato, Cepof’s coordinator. ing 70 fulltime researchers and anoth- November 2005.“We’ve already sold The traffic light uses four LEDs and has er 50 collaborators or associates, has, nearly 15,000 lamps, which have been a design that takes advantage of all the over the last few years, been research- installed in traffic lights in São Paulo light refraction.“We have already reg- ing and developing a series of other and Guarulhos”,says Alberto Monteiro, istered a patent for the full equipment pieces of equipment that employ this the owner of Meng, a company that spe- and as far as we know, no other group light source, which was discovered in cializes in the manufacture of devices in Brazil or abroad is manufacturing the 1960s (see the box on page 73).“The for the highway, urban and industrial traffic lights like ours.” process for producing light in LEDs is signaling sector. Named ‘blackout’,in reference to “The use of the LED-based lamp in the fact that it does not go out when traffic lights brings with it a series of there is a power cut, the device uses advantages, because it’s more econom- four high-brightness LEDs,(light-emit- ical, safer and more efficacious, in ad- THE PROJECT ting diodes) in each light (red, yellow dition to lighting better. All this with- and green). A plastic lens with a special out mentioning the fact that the optical design distributes the light and Technological innovation ‘retrofit’ has a long working life, there- program of the São Carlos emits the desired luminous effect. Ac- Optics and Photonics by reducing the maintenance costs of cording to Bagnato, one of the biggest Research Center (Cepof) the traffic light by up to 80% and the advantages of the new technology is the frequency with which the lamps are safety factor it will bring to road sys- MODALITY changed. In conventional lights the tems in cities.“It’s going to reduce the Innovation and Diffusion green and red lamps, which stay alight probability of accidents and traffic Research Center (Cepid) longer, are changed around four times a year and the yellow lamps, twice. Their chaos caused by small blackouts a lot, COORDINATOR particularly in large cities, like São VANDERLEI SALVADOR BAGNATO – USP cost varies from R$ 4 to R$ 8, totaling Paulo, where traffic flow is intense”,he nearly R$ 60 annually, quite apart from says. The product is in its finishing INVESTMENT the costs incurred with maintenance stage and the group from USP is al- R$ 200.000,00 per year (FAPESP) and exchanging the lamps. With the ready contacting companies that oper- ‘retrofit’ one inspection visit a year is 62 ■ SPECIAL ISSUE NOV 2006/SEP 2007 ■ PESQUISA FAPESP 60-65_Optica_139_Ing 12/11/07 15:18 Page 63 enough, because each lamp lasts from between three to five years”,Monteiro emphasizes. Each ‘retrofit’ lamp costs nearly R$ 500, which is a total of R$ 1,500.00, when divided by four years (on average), is R$ 375 per year.“With the reduction in visits to the traffic light and the maintenance costs, the instal- lation of LEDs gives a return in around one and a half years”,says Monteiro. The lighting efficiency and durabil- ity (more than 50,000 hours, 50 times longer than conventional lamps) are two important differences that LEDs have. They also have another compar- ative advantage: the low environmen- tal impact of the production process. Fluorescent lamps, always remembered as offering an alternative that is more Auxiliary LEDs economic than incandescent lamps, use for lighting mercury, which is a highly toxic sub- operating theaters stance.“These factors have led to the ex- plosive growth in research over the last five years and various companies are launching more and more high-bright- ness LEDs and products based on them, in a great variety of combinations”, the quotations of shares traded on the by former researchers from the center, points out physicist, Henrique de Car- North American technology stock ex- has developed two auxiliary emergen- valho, a member of the Cepof team. change. According to the researchers cy lighting models using LED technol- Residential and urban lighting are from USP in São Carlos, in the resi- ogy. “The first batch of 25 units was two areas that have benefited greatly dential area it is possible to substitute bought by Cepof itself, which installed from the development of LED technol- all lighting with LEDs, both internally them in their laboratories. The second ogy. Street lighting using light-emitting and externally, without losing intensi- batch of 100 lamps should go on sale in diodes and planned by Cepof is already ty, improving illumination quality and September”,says electrical engineer, being tested in São Paulo. In New York, reducing energy consumption. Alexandre Oliveira, one of the seven there is an example in the huge screen Emergency lights (those that are ac- partners of Direct Light, which was on the NASDAQ MarketSite Tower, in tivated when there is a power cut) are founded just one year ago. Times Square, in the center of the city, also a promising application for LEDs. The lamp uses just one 3 watt LED which uses 18.6 million LEDs to deco- In a partnership with Cepof, Direct and works for one hour with 70% rate the front of the building and to give Light from São Carlos, which was set up lighting intensity.“In addition to be- ing more compact, our lamps use a nickel-metal hydride rechargeable bat- tery that lasts at least twice as long as the sealed lead acid batteries used in the emergency lights found in the mar- ket”, explains Oliveira. The product costs nearly R$ 90, a similar price to that of a quality emergency light made by competitors. The price is still high but the tendency is for it to fall as pro- duction increases. The dentist’s surgery – LED technol- ogy has also been used in developing various products used in the medical Odontological odontological area, such as, for exam- reflector ple, mouth lights for dental surgeries, a developed segment that is also being focused on with Gnatus by Cepof.According to Bagnato, the de- PESQUISA FAPESP ■ SPECIAL ISSUE NOV 2006/SEP 2007 ■ 63 60-65_Optica_139_Ing 12/11/07 15:18 Page 64 and which concentrate in the tumor cells. The reaction kills the tumor.“The robustness of the apparatus is a result of the low maintenance that is need- ed, which gives our product yet anoth- er point of difference.And all this with- out mentioning that the LED, because it emits a less concentrated light, man- ages to treat a greater area of the pa- tient’s skin, while the laser is more pin- pointed”,explains Ribeiro.“This is the first and only device using LED tech- nology made in Brazil for photody- namic therapy.” The equipment’s success has meant that Bagnato and his team have devel- oped a new version of the device.