| 摘要 |
An illuminated sign, readable during the night or day, and suitable for use as a house number display, uses a single illuminatable panel, on which a number of stencils are plac critical flicker frequency ed. Each stencil is a rectangular piece of opaque material, such as plastic or metal, in which a central cutout is made in the shape of a number. Several of these stencils are arrayed in front of the illuminatable panel, so that only the light coming through the central cutouts is visible through the stencils. The illuminatable panel is made of an array of LED's, with a diffuser to produce a uniform illumination, and is powered by one or more batteries. A light detector senses the onset of dusk, which activates the illuminatable panel, turning it on, and leaving it on for four or more hours. A constant-current electronic system powers the LEDs, which are pulsed on and off at a speed greater than 90 Hz, which makes the sign appear to the human eye as constantly illuminated. A timer leaves the illuminatable panel illuminated only for a few hours, in order to maximize the life of the batteries.
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