low pressure sodium bike light?
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2xTrinity
Flashlight Enthusiast
The same reason people haven't made bike lights out of 4 foot U-bend fluorescent tubes...
the high pressure sodium lamp is a long lube, that would be bulky, fragile, and completely impossible to focus into a beam.
Not only that, monochrome yellow light really sucks, no matter how many lumens you have of it. Most of the street lighting in my area is low pressure sodium, with the occasional metal halide (the bright white lamps used in HID vehicle headlights) interspersed here and there. Despite their lower lumen output, the metal halides are FAR more effective at allowing me to actually SEE things like obstructions in the road. For example, it's sometimes hard to tell the differece betweeen say a large leaf or a rock when everything is just shades of yellow.
Neutral white LEDs (even better than the metal halides I described as far as color rendition/bike illumination) are available at nearly 100 lumens per watt now. With good optics, your bike light will almost certainly be more efficent at extracting and delivering those lumens where you need them to be, than a bulky sodium lamp could be.
the high pressure sodium lamp is a long lube, that would be bulky, fragile, and completely impossible to focus into a beam.
Not only that, monochrome yellow light really sucks, no matter how many lumens you have of it. Most of the street lighting in my area is low pressure sodium, with the occasional metal halide (the bright white lamps used in HID vehicle headlights) interspersed here and there. Despite their lower lumen output, the metal halides are FAR more effective at allowing me to actually SEE things like obstructions in the road. For example, it's sometimes hard to tell the differece betweeen say a large leaf or a rock when everything is just shades of yellow.
Neutral white LEDs (even better than the metal halides I described as far as color rendition/bike illumination) are available at nearly 100 lumens per watt now. With good optics, your bike light will almost certainly be more efficent at extracting and delivering those lumens where you need them to be, than a bulky sodium lamp could be.
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LukeA
Flashlight Enthusiast
gentlegreen
Newly Enlightened
Not a linear fluorescent, but I reckon I win the eccentic crown for the lamp I made one from a sawn-off 9 watt minispiral warm white fluorescent powered by a 12 volt single transistor invertor that originally powered twin 6 inch tubes.
In spite of its totally unfocussed beam pattern, it was very effective in town.
After 2 winters it's only just this week been replaced with a new "be seen" 4 watt, 48 LED lamp :-
I will be fitting an MR16 multi-LED in the centre, and I have now added a second 40mm plumbing fitting underneath for a 5 watt 10 degree MR16 LED spot.
In spite of its totally unfocussed beam pattern, it was very effective in town.
After 2 winters it's only just this week been replaced with a new "be seen" 4 watt, 48 LED lamp :-
I will be fitting an MR16 multi-LED in the centre, and I have now added a second 40mm plumbing fitting underneath for a 5 watt 10 degree MR16 LED spot.
cbr2702
I think that is a pretty reasonable question, and a few years ago (before powerful leds existed commercially) I had a really good look at this subject.
My conclusions were:
low-pressure sodium technology does not have to be a long tube - it could be a small light source only a few mm across.
Existing LPS lamps are highly, and cleverly, optimised for street lighting.
It would be a major development programme to make a reasonably efficient LPS lamp of a few Watts, requiring materials, chemical and electronics expertise.
The right person could probably do it on their own, but it would be a labour of love.
In the end, you would have a focussable light source, but it would still be monochromatic (actually dichromatic) yellow.
When bright leds came along, I completely stopped thinking about this subject - until you reminded me!
BTW 2xTrinity - low and high pressure sodium lamps are significantly different.
Steve
I think that is a pretty reasonable question, and a few years ago (before powerful leds existed commercially) I had a really good look at this subject.
My conclusions were:
low-pressure sodium technology does not have to be a long tube - it could be a small light source only a few mm across.
Existing LPS lamps are highly, and cleverly, optimised for street lighting.
It would be a major development programme to make a reasonably efficient LPS lamp of a few Watts, requiring materials, chemical and electronics expertise.
The right person could probably do it on their own, but it would be a labour of love.
In the end, you would have a focussable light source, but it would still be monochromatic (actually dichromatic) yellow.
When bright leds came along, I completely stopped thinking about this subject - until you reminded me!
BTW 2xTrinity - low and high pressure sodium lamps are significantly different.
Steve
gillestugan
Enlightened
I'm not sure I would like to have it in a bike light or a flash light as I usually use those when it is pitch dark.
The human eye response to orange colours in low light conditions is very low.
This is because the rods in the eye, which are used in scotopic vision, is most responsive to colder light (dotted line).
The human eye response to orange colours in low light conditions is very low.
This is because the rods in the eye, which are used in scotopic vision, is most responsive to colder light (dotted line).
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2xTrinity
Flashlight Enthusiast
Thanks for point that out. I am aware of the difference. I made a typo in my earlier post. I said high pressure sodium, but meant to say low pressure sodium.
The lights in my area are, in fact, low pressure sodium (ie long u-shaped tubes producing monochrome yellow light), not high pressure sodium.
Interesting graph. One thing to note is that our vision is not binary. Only in extremely dark situations, ie wilderness with no moon, is our vision completely scoptopic. Under most "flashlight use" situations, our eyes will be using some combination of both. Either way though, amber are much poorer lumen for lumen. Even high pressure sodium with its somewhat broader spectrum does dramatically better than LPS in my opinion.
In my experience, I've found the neutral white light (3500-4500k range) to be the best overall for seeing with at night outdoors. This is based mostly on my subjective experience rather than actual theory. Incidentally, natrual moonlight tends to fall in this range as well, and in the absence of obnoxious yellow city lighting conditions, it's possible to see quite well under a full moon, even incuding a slight amount of color rendition. A keychain light producing only a few lumens in a flood pattern can produce full moon intensity. An amber LED producing just as many lumens in daylight conditions, would be much harder to see with, all else equal.
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