Light emitting diodes 185 Electric lighting 28 Microcontrollers 26 Materials 21 Design and construction 15 Electroluminescent devices 13 Lighting 13 Semiconductors 13 Electric lamps 12 Equipment and supplies 12 Gallium nitride 12 Design 11 Diodes, Semiconductor 10 Electric properties 8 LED lighting 8 Semiconductor lasers 8 Polymers 7 Automatic control 6 Clocks and watches, Electric 6 Electronic traffic controls 6 Instruments 6 Process control 6 Electronic apparatus and appliances 5 Photovoltaic power generation 5 Programmable controllers 5 Hydroponics 4 Information display systems 4 Liquid crystal devices 4 Solar energy 4 Traffic engineering 4