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For the rest of this comment I am going to assume an LED is a single P-N junction. Regarding reverse voltage: Most if not all LED manufacturers will list an absolute maximum reverse voltage as 5V. Yet, many people are driving LEDs directly from an AC power line (120V or 240V) with a resistor for current limiting.
One-color light is well suited for traffic lights and signals, exit signs, emergency vehicle lighting, ships' navigation lights, and LED-based Christmas lights Because of their long life, fast switching times, and visibility in broad daylight due to their high output and focus, LEDs have been used in automotive brake lights and turn signals.
Twilight occurs according to the solar elevation angle θ s, which is the position of the geometric center of the Sun relative to the horizon. There are three established and widely accepted subcategories of twilight: civil twilight (nearest the horizon), nautical twilight, and astronomical twilight (farthest from the horizon).
A photoelectric sensor is a device used to determine the distance, absence, or presence of an object by using a light transmitter, often infrared, and a photoelectric receiver. They are largely used in industrial manufacturing. There are three different useful types: opposed (through-beam), retro-reflective, and proximity-sensing (diffused).
New street lighting technologies, such as LED or induction lights, emit a white light that provides high levels of scotopic lumens. It is a commonly accepted practice to justify and implement a lower luminance level for roadway lighting based on increased scotopic lumens provided by white light.
The time of dusk is the moment at the very end of astronomical twilight, just before the minimum brightness of the night sky sets in, or may be thought of as the darkest part of evening twilight. [4] However, technically, the three stages of dusk are as follows: At civil dusk, the center of the Sun's disc goes 6° below the horizon in the ...
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