At civil dawn and at civil dusk sunlight clearly defines the horizon while the brightest stars and planets can appear. Enough illumination renders artificial sources unnecessary for most outdoor activities. Under clear weather conditions, civil twilight approximates the limit at which solar illumination suffices for the human eye to clearly distinguish terrestrial objects. The collateral adjective for twilight is crepuscular, which may be used to describe the behavior of animals that are most active during this period.Ĭivil twilight in a small town in the Mojave Desert For example, very old people may be said to be "in the twilight of their lives". Owing to its distinctive quality, primarily the absence of shadows and the appearance of objects silhouetted against the lit sky, twilight has long been popular with photographers and painters, who often refer to it as the blue hour, after the French expression l'heure bleue.īy analogy with evening twilight, the word twilight is also sometimes used metaphorically, to imply that something is losing strength and approaching its end. When the Sun again reaches 18° below the horizon, nighttime becomes morning twilight. When the Sun reaches 18° below the horizon, the twilight's brightness is nearly zero, and evening twilight becomes nighttime. The lower the Sun is beneath the horizon, the dimmer the twilight (other factors such as atmospheric conditions being equal). The word twilight can also refer to the periods of time when this illumination occurs. Twilight is light produced by sunlight scattering in the upper atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. But it's not difficult for me to see how PIR lights might be the source of some frustration.Evening twilight: civil, nautical, and astronomical stages at dusk. My initial erroneous settings were rectified the next day. And "Detection Area" of anything over 10% meant that a neighbourhood cat sashaying into my driveway (30 feet from my front door) was going to turn the light on. Keeping the light on ("Hold Time") for 20 minutes was stupid for all sorts of reasons. "50 Lux" means anything after late afternoon. I got the ambient light setting way too high. And, needless to say, my first settings of the DIP switches were horribly wrong. To be honest, I was a little amused to see DIP switches in this application, because I kinda thought they'd gone the way of parallel ports and floppy disc drives.
DUSK TO DAWN LIGHT SERIES
The light I chose used a series of DIP switches to set these parameters. And the range of area where it will respond to motion. The level of ambient light when it will turn on.
This sort of PIR light generally has three variable settings: How long the light stays on when triggered. The new fixture not only looks a lot nicer than the one it replaced, but it gives much better lighting at my entranceway, and makes it a lot easier for me to open my front door when I come home late at night. I just replaced my existing fluorescent porch light with a PIR-enabled LED fixture. IMHO they are the original "smart light" solution. When they are well set up, and used in the right environment, then they are fantastic. It's impossible to make any sort of broad recommendation on these things. There's a reason you won't find LED traffic lights in a lot of places. But there are a few things they don't do quite as well as incandescents. They are great from a longevity and energy-efficiency standpoint.
DUSK TO DAWN LIGHT DRIVER
IOW: It would be cheaper to buy a new light, engineered for LEDs, rather than trying to retrofit an LED driver into the existing fixture.Ĭlick to expand.Glad everything worked out. But the cost and complexity of doing that is probably such that it becomes uneconomical. You could eliminate the flickering of your light by adding a constant-current power supply. That's what goes into the complex circuits I've got in my newly-installed LED PIR security light. LEDs are usually designed to be connected to a driver, designed to provide it with constant voltage. And this is where LEDs are particularly susceptible to "flicker." The "dim" colour of the bulb in its idle state, means the bulb is seeing lower voltage. Get it up to 100hz - and you probably wouldn't notice it. LEDs don't have "persistence." And, for whatever reason, the 50hz (call it "fifty flickers per second") cycle is just about what the human eye and brain can detect. It's just that older bulbs have what is known as "persistence." The filament/whatever stays hot enough during the phase transition that your eyes don't notice it.
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