Dave Fawthrop said:On Mon, 6 Feb 2006 20:25:04 -0000, Fran <[email hidden]>
wrote:
Quoted message said:|Take a look at this - and then can someone please tell me why on /earth/
|a *lamppost* of all things would need anything as high tech as a GPS to
|tell it when it's getting dark?
|
|http://www.stwol.com/english/index.htm
Quoted message said:But it does *not* detect when it is raining and dark. The present ones
work on ambient light intensity and have done for 30 years to my certain
knowledge.
It's an interesting example of what happens when you specify a problem
incorrectly to an engineer. Someone asked an engineer to design
something that would turn lights on and off at the appropriate time
shifts from sunrise and sunset. So this thing finds out where it is,
calculates local sunrise and sunset times, and is never wrong and
never needs adjusting.
But the whole "half hour before sunset" thing is an attempt to frame a
law which catches the otherwise rather nebulous "when the light starts
going", the most frequent cause of which is the sun going down. But of
course it's also wise and useful to light up during heavily overcast
days, eclipses, and so on. Which can all be solved be a simple cheap
light sensor.
It's the same kind of idiocy as that which specifies legally allowable
lights for bikes, cars, etc. in terms of the wattage of the bulb. Not
to mention the lunacy of specifying car racing classes in terms of
engine capacity, which has led to our modern highly inefficient and
expensive high-revving engines which try to squeeze the most power out
of a given capacity. If the idiots who did that had instead specified
racing classes in terms of the size of petrol tank, we'd now have a
lot more oil left and lot less polluted an environment.
--
Chris Malcolm [email hidden] +44 (0)131 651 3445 DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]