Looking at a blinking yellow warning light, I got to thinking about how to mark any heavy cabling to secure the Temple during the event. In day, there is less concern as simply adding some ribbon would work. At night I thought to have a LED projection along the length of the cable. Then I figured side-emitting fiber-optic cords would be nice, lit green for optimal visibility. This led me to spiral the fiber-optics, and it would kind of look like a vine climbing, perhaps like an electronic morning glory.
On the technical side, I figured 1 watt of LED light would be plenty, but I'd like to have a redundant pair on each cable. This would mean about 10 watt-hours each per night which could be recharged by a 2W solar cell. But for the sake of using 10 watt-hours for, say, 8 nights, that's just 80 watt-hours. Quality alkaline D-cell batteries are typically 10 amp-hours at 1.5V or about 15 watt-hours each, so it would take a minimum of 6 batteries to hit that mark. A simple resistor circuit could drop a series-parallel pack wired for 4.5 volts to the necessary 3.5 volts at 280mA[1. Estimated from Luxeon Star-III specification sheet, rated for 700mA @ 3.5V = 2.5W]. The current would draw symmetrically (theoretically) from each chain of 4.5V, so the runtime on the battery would be a total of 10AH / 0.14A = 71 hours. (The discrepancy from 90 hours is because it's 280mA at 4.5V which is more like 1.3W. What will happen, though, is the light will get slightly dimmer and the battery last longer. The resistor is fixed at 1V / 280mA = 3.6Ω, so when the battery has dropped to 4V, the resistor drop is only 0.5V, and so the current is 0.5V / 3.6Ω = 140mA.)
I guess that got way too technical too fast. Oh well.
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