Switch circuit controls lights

摘要

Cities and towns worldwide are considering and installing LED streetlights to help save electric energy, reduce costs, protect the environment, and improve lighting for their citizens. Despite this trend, the lamps' turn-on/ turn-off time control is receiving little attention. A suitable control can achieve an important energy saving because lights can operate too late, too early, or both, wasting energy or providing insufficient light. Using a twilight switch can is not prone to contact oxidation. It uses a TRIAC (triode alternating current) that can switch hundreds of watts. The circuit requires little power. It uses a charge pump to feed the circuit from the ac line, drawing less than 37 mW for a 220V-rms ac line. It uses just a few low-cost components.