LED Lights and Lumens
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Black Sheep
Well-known member
Interesting question.
According to http://en.wikipedia.org/wiki/Incandescent_light_bulb filament bulbs run from 12.6 lumens per watt (40 Watt) to 17.5 lumens per watt (100 Watt). It doesn't suggest efficiency at lower wattages, but it looks like a 4 watt bulb ought to be around 8 lumens per watt. So to get 50 lumens you'd need around 4.5 watts. (ie around a third of an amp at 12 volts).
Someone more technical will be along in a minute to tell me why I can't extrapolate the efficiency curve down to 4 Watts. And there do seem to be some odd figures down there. But I've just found a 5 Watt 12V filament lamp at CPC that claims 50 Lumens. So we've got to be in the right ballpark.
According to http://en.wikipedia.org/wiki/Incandescent_light_bulb filament bulbs run from 12.6 lumens per watt (40 Watt) to 17.5 lumens per watt (100 Watt). It doesn't suggest efficiency at lower wattages, but it looks like a 4 watt bulb ought to be around 8 lumens per watt. So to get 50 lumens you'd need around 4.5 watts. (ie around a third of an amp at 12 volts).
Someone more technical will be along in a minute to tell me why I can't extrapolate the efficiency curve down to 4 Watts. And there do seem to be some odd figures down there. But I've just found a 5 Watt 12V filament lamp at CPC that claims 50 Lumens. So we've got to be in the right ballpark.
ianat182
Well-known member
Not a technical reply but one I've just read from the Force 4 Catalogue which states that for a 1.2watt consumption their Superbright chip LED bulbs give a light output of 10watt Halogen. These replace the G4 halogen with side pins or the G4 with back pins;there are also Dichroic LED that replace the MR11 and MR16 halogen versions. Each has 7chips.
Hope this helps .Prices are £18.50 each (all 12v)
ianat182
Hope this helps .Prices are £18.50 each (all 12v)
ianat182
Gwylan
Well-known member
It's all about a trade off between life and lumens - there are no free lunches. High lumens then lower life or some other drawback.
The transition from filament or halogen to LED is not straightforward. There is the issue of 'colour'
LED's generally are classed by their colour temperature. Daylight does not generally mean anything we might recognise as daylight.
Most of the manufacturers are creative in the colour, life and lumens that they publish.
People will tell you about the 100 lumens per watt that LEDs are giving out, but they won't mention that this is measured under lab conditions and under the best possible arrangement for the LED.
Without some reasonable optical system then you will not get the full benefit of the energy reduction or your investment. This is because LEDs are a small very bright source that is great for illuminating lap top screens and the like but not the greatest for your saloon or kitchen.
Best to buy a reputable brand but do not expect the same effect that you have enjoyed up to now with halogen or filament lamps.
Having said all that I've just replaced the 'festoon' lamps in the fittings in the saloon - the ones that everyone leaves on.
Everyone looks like zombies with that unhealthy pale blue complexion. Reduced the load on the batteries and put up the amount of light escaping from the front of the fitting - but it looks dreadful.
Really need an LED fridge now - that's what eats the power with us
The transition from filament or halogen to LED is not straightforward. There is the issue of 'colour'
LED's generally are classed by their colour temperature. Daylight does not generally mean anything we might recognise as daylight.
Most of the manufacturers are creative in the colour, life and lumens that they publish.
People will tell you about the 100 lumens per watt that LEDs are giving out, but they won't mention that this is measured under lab conditions and under the best possible arrangement for the LED.
Without some reasonable optical system then you will not get the full benefit of the energy reduction or your investment. This is because LEDs are a small very bright source that is great for illuminating lap top screens and the like but not the greatest for your saloon or kitchen.
Best to buy a reputable brand but do not expect the same effect that you have enjoyed up to now with halogen or filament lamps.
Having said all that I've just replaced the 'festoon' lamps in the fittings in the saloon - the ones that everyone leaves on.
Everyone looks like zombies with that unhealthy pale blue complexion. Reduced the load on the batteries and put up the amount of light escaping from the front of the fitting - but it looks dreadful.
Really need an LED fridge now - that's what eats the power with us
noelex
Well-known member
- Joined
- 2 Jul 2005
- Messages
- 4,140
High lumens and long life are certainty possible although many, many companies use very old inefficient emitters and then compound the problem with poor heat sinking.
Good Leds are getting too bright for boat use and need to under driven, to keep the illumination level reasonable.
I have some homemade lights and the LED emmiter will put out 800 lumens!. I drive it at only 0.1A, only a fraction of its rated current, and get a very nice light of about 100 lumens.
Robih
Well-known member
LED tape
I've had some considerable success with LED tape; see here: http://www.ultraleds.co.uk/60pm-1500-lumen-warm-white-tape-metres-p-2280.html
Because it's a long length it effectively lights large areas of the boat, we have it in the galley and the saloon. I don't have any direct view of the LED's though; they would be too bright to look at. However as downlighters and bouncing the warm white light off the teak surfaces they deliver a very pleasant ambiance. No complaints at all. Power consumption reduced by about 60% on the halogens that were there before.
rob
I've had some considerable success with LED tape; see here: http://www.ultraleds.co.uk/60pm-1500-lumen-warm-white-tape-metres-p-2280.html
Because it's a long length it effectively lights large areas of the boat, we have it in the galley and the saloon. I don't have any direct view of the LED's though; they would be too bright to look at. However as downlighters and bouncing the warm white light off the teak surfaces they deliver a very pleasant ambiance. No complaints at all. Power consumption reduced by about 60% on the halogens that were there before.
rob
I've replaced most on the boat from here -
http://www.bedazzled.uk.com/12v_LED_Bulb_Replacement.htm
The 9 smd festoons .FESTOON-42mm-9L. are, well, pretty bright! They are said to be 145l ( warm light) Not sure what wattage the halogens were before but 150l and above works fine for me. Plenty light, nice and warm as well. I've got one ofthese over the galley, G4W-15L. No ties with the company etc but really glad I found them.
VicS
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- Joined
- 13 Jul 2002
- Messages
- 47,670
The old 60 watt (240 volt) pearl bulbs were labelled 700 lumens
60 watt clear bulbs are labelled 670 lumens
But the light from a simple filament bulb is distributed in all directions. The light from an LED is concentrated into a fairly narrow cone. So the illumination of a surface by a LED will much greater than by a filament bulb.
So to compare them you need to know the solid angle, in steradians, through which the light from an LED is distributed and compare that with the 4pi (12.56637) steradians of a complete sphere
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jrt
New member
Why not just buy one, take it down to your boat and see what effect it has. Go for the 'warm white' rather than the blue white or cold white.