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any more bad mathematicians out there

pierre_pierre
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Registered: 30-07-2007

any more bad mathematicians out there

Kent has been changing the light bulbs in traffic lights, cost £1.7M  annual saving £150,000  redemption time nearly 12 years
http://news.bbc.co.uk/1/hi/england/kent/8204230.stm
Quote
Kent County councillor Nick Chard added: "The switch from existing halogen lamps will result in substantial financial and environmental savings.
24 REPLIES
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Re: any more bad mathematricains out there

And surely the better thing to do would be to replace them as and when the existing ones in the traffic lights failed?
Will Moderate For Thanks
Lurker
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Re: any more bad mathematricains out there

I understood there were also arguments in favour of their [LED] higher visibility too
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Re: any more bad mathematricains out there

I suspect bad reporting rather than bad arithmetic at the council.  Wink
There are significant saving on maintenance as the new units last much longer, need checking less and replacing very rarely.
But that's probably not as "newsworthy" as the green angle.

And anyway, the recovery period should also allow for interest rates (yes I know they're fairly low at present).
Loombucket
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Re: any more bad mathematricains out there

Quote from: James_G
I understood there were also arguments in favour of their [LED] higher visibility too

There were, but as I (and most other Kent residents) can see sod-all difference after the bulbs were changed, I think we can regard that as a bit of a non-issue.   Smiley
I'll bet all you lot who have the misfortune to live other than in the Garden of England are dead jealous of us lucky people who have lovely shiny green traffic light bulbs...and red and amber ones, too....
[Wanders off back into the arms of the psychiatrists, sobbing]
Lurker
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Re: any more bad mathematricains out there

The ones in Leeds seem to have been switching over too, but I'm not certain whether its a phased changeover, or simply a replacement of LEDs in place of incandescent lamps as they need replacing.
Leeds council have been making a lot of noise about all the street lights they've changed over though.
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Re: any more bad mathematricains out there

Another benefit is that an individual LED can fail, but the rest of the LEDs in the 'bulb' continue to function.
B.
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Re: any more bad mathematricains out there

I was at a junction today (on A41 north of Watford) where the lights on the "stop" line were incandescent but the repeaters across the junction were LED's. Made me wonder if they had "plug-in" replacements or had just missed one.
It was mildly more interesting because I was in a filter lane so one had a partly-obscured glass to produce the arrow, the other just an arrow of LED's on the green. [\Exit nerd mode]
Lurker
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Re: any more bad mathematricains out there

And could you see a difference in brightness?
Presumably there must be a difference, since the incandescent 'filter' lamps had to be larger so that you could still make out the arrow, whereas the LED replacements are the same size as the other lamps in the cluster.
?
itsme
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Re: any more bad mathematricains out there

Quote from: Barry
Another benefit is that an individual LED can fail, but the rest of the LEDs in the 'bulb' continue to function.
B.
Would not assume that. It's dependent whether they are wired in series or parallel. If wired in parallel then yes if any individual LED fail then it will not affect the others but the current requirement will be higher. If wired in series then if one LED fail it will knockout the others in the same series circuit. If wired in series the current requirement will be less but the voltage have to be higher.
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Re: any more bad mathematricains out there

I'm not assuming it - I've seen a couple of the newer LED 'bulbs' in our area with dead LED's.
Of course, a failure in the unit itself may knock the bulb out completely, but the failure of a single LED should, in most circumstances, allow the remaining ones to keep functioning.
B.
itsme
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Re: any more bad mathematricains out there

Not if wired in parallel. I used LCD's with backlighting on battery powered devices they were a combination of both i.e 4 parallel circuits each with 2 LED's in series.
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Re: any more bad mathematricains out there

It seems to be widespread throughout the country.
http://www.electronicsweekly.com/blogs/led-lights/2009/05/whats-the-big-deal-with-led-traffic-lights...
http://www.howstuffworks.com/question178.htm
andf I wouldn't imagine for a minute that a piece of equipment that needs to fail safe - would wire lights in series, so a lamp would just degrade over a period as individual LED's fail. There would be inbuilt alarms anyway that monitor the current and if it falls below a certain value would trip an alarm.
They have been installed on the railways for some time too where fail safe mechanisms are even more important.
They've signalled Edinburgh Waverley a year or two back and now they have these LED signals and they are noticeably brighter - especially in bright daylight.
They seem to be installed new cars as well - so hopefully less cars with only one rear red light.
pierre_pierre
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Re: any more bad mathematricains out there

They have done another bad one in Chelmsford, went down a rat run side road (Lawn Lane)yesterday and driiled the road, inserted the plugs, screwed down the sleeping policemen road humps, 17:30 a gang of workmen came and removed them, wrong size
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Re: any more bad mathematricains out there

Quote
any more bad mathematricains out there

Few bad spellers though...... Wink