| 摘要 |
PURPOSE:To prevent erronous detection of environmental temperature, and to prevent repetive low brightness lighting and illumination by adjusting the brightness of the lighting of low brightness so that the environmental temperature at the time of lighting of low brightness does not exceed a predetermined value, when detecting the environmetal illuminance by an illuminance sensor at the time of changing from illumination of a foodlight to the lighting of low brightness. CONSTITUTION:When a detection analog signal of emvironmental illuminance is bright enough, the output of an illuminance detection sensor 7 is not more than a floodlight level, and no signals of low or high brightness are generated by a CPU 9, while a floodlight 1 is illuminated. When the environmental temperature reaches no more than a predetermined low brightness lighting illuminance level at dusk, the output of the sensor 7 becomes higher than the low brightness lighting level, and a low brightness lighting signal is sent to a light adjustment circuit 10 by the CPU 9. The floodlight 1 is thus lighted at low brightness. The output of the sensor 7 is surveyed in the middle of this lighting at low brightness, and the brightness at the time of low brightness lighting is changed so that the output of the sensor 7 becomes no less than a threshold of illuminance at the time of low brightness lighting, when the value of the output is no more than the threshold of the low brightness lighting. |
