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8430Re: [rootsradicals] Re: Bicygnals

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  • David Chase
    Mar 5, 2009
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      On 2009-03-05, at 10:52 PM, adventureboyseven wrote:
      > My plan is to hack a red rear flasher and mount the LEDs on the top
      > of a flag and run the wires down the mast to a custom battery pack
      > at the flags base. If they know you are there that is enough.
      > When I ride I pretend that all the car drivers are trying to kill
      > me, and that way nothing surprises me, and therefore I am safe to a
      > larger degree.
      > Motorcyclists get creamed by cars and trucks all the time and they
      > have full lights, think about it.
      I think about it quite a bit. My cousin was killed in a motorcycle
      accident, and my wife, stopped at a stoplight in a Toyota Camry, was
      rear-ended by someone who was too busy to notice the red light and
      stopped car.

      At one of the electronics sites that I sometimes visit (Sparkfun.com),
      I did in fact look at the "proximity detectors", to see if there was
      anything that could pick up a car at a sensible distance, and trigger
      some serious lights.

      I rode home tonight in actual dark, using the hub powered lights, with
      the excess-power-shunt shunting spare power into an LED puck capable
      of dumping as much as 9 watts. Because of the cold weather and the
      heat-sinking, the dump LED flashes (*), erratically, but faster as I
      go faster. It was un-be-lievably obnoxious -- it was a nearly
      pessimal combination of annoying rate, annoyingly unpatterned, and
      bright. It is so awful, I cannot really us it anywhere on the bike.

      (*) The reason for the flashing is an electrical-thermal oscillation.
      Cold LEDs require a higher voltage before they will conduct/light up.
      So, the voltage goes a little higher than normal before the light
      comes on. But as soon as it comes on, it heats up the LED locally,
      and reduces the voltages needed to run the LED, so it can stay on as
      the voltage drops (for a bit), until the shunt turns off. And then,
      because it is mounted to a heat sink in a 10-15mph freezing-
      temperature wind, it cools off fast, faster than the voltage to turn
      it on again can build up, till it sits at a plenty-cold temperature,
      the voltage builds enough, and it starts over again.
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