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Old 29 April 2005, 08:13   #1
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LEDs

Does anyone know of a laymanís way to compare the output of an LED with a conventional bulb LEDs are measured in Mcd and bulbs tend to be measured in watts, I know what to expect from a 50w bulb whereas I donít know what a 2000 Mcd LED is capable of. Des
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Old 29 April 2005, 10:04   #2
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Not sure I can really answer this one properly, but a Candela is the amount of light falling on a sq m of surface at 1m from the light source.... I think. So 2000mcd must be the same as 2 cd. Anyway, that probably doesn't help much. You could always buy a cheap phototransistor from Maplin and connect an ohmeter to it and compare the resistance between the two light sources. Don't forget also that LED's tend to have a fairly directional beam.
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Old 29 April 2005, 10:44   #3
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As Erin says they are very directional - almost like a laser beam. Also they tend to emit light quite near to infra red wavelengths so can be far more sensitive to things like ccd cameras etc than the human eye.

http://www.ngineering.com/LED_Calculators.htm

Some nifty brightness calculators and info here.

I have noticed that my LED torches will barely illuminate the surface of the sea due to the wavelength of the light.

Of course main advantages of LEDs are low battery consumption and very long life(100,000hrs).

Has anyone noticed the LED catseyes down Plymouth/Portsmouth way???
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Old 29 April 2005, 11:05   #4
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Des

Try this

http://www.gizmology.net/LEDs.htm

Mark
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Old 29 April 2005, 17:58   #5
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Quote:
Originally Posted by codprawn
Has anyone noticed the LED catseyes down Plymouth/Portsmouth way???
Err, isn't that a contradiction - I thought that the point of "cats eyes" was that they just reflect light, exactly like a cat's eye, not act as a source???
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Old 29 April 2005, 18:08   #6
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Quote:
Originally Posted by Richard B
Err, isn't that a contradiction - I thought that the point of "cats eyes" was that they just reflect light, exactly like a cat's eye, not act as a source???
To be honest they weren't that effective either - looked WILD though!!! Don't know how good they are for road safety though - i found I could drive at 70mph in total darkness and still see where the road was going!!!!!!!!!!!!!

On the same subject I don't know if other people have noticed how few roads have cat's eyes these days - they just don't seem to bother replacing them - great for road safety - suppose they need the money for speed humps.............
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