Some Speculation About Practical Phosphors

In theory, the way fluorescent light-bulbs work, is that they already have a light-source of shorter wavelength – and therefore of higher photon-energy – to excite a phosphor, the latter of which emits a pleasant mixture of wavelengths of light – in general, longer wavelengths than that of the energy-source; any mixture of phosphors will do. The light source is allowed to be a Blue LED, rather than a UV light-source.

What I discover in practice, is that the choice of phosphors manufacturers can work with is rather limited. For LED-Light-Bulbs that are stated to produce a color-temperature of 2700K, they tend to use “Y3Al5O12Ce”. Additionally, I have discovered the availability of a newer type of light-bulb, as shown in this photo:

foxy_150409180629

In which a higher voltage is applied directly to an Electroluminescent material.

What strikes me as both convenient and remarkable about these light-bulb-types, is that The color matches very closely. What this observation would seem to suggest, is that the EL material used in the newer light-bulb-type is a hard crystal, that matches the composition of the phosphors used in the LEDs, mentioned above. Additionally, this would seem to suggest, that the layer of the phosphors used in the LED-Light-Bulbs described as having 2700K color, is rather thick, so that very little of the Blue LED’s light passes through, since the light produced via EL has no Blue LED to modify its color-quality.

I suppose then, that the manufacturers have simply added another substance to this phosphor – in small quantities – that causes it to become conductive.

Dirk

 

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I could make a loose inference, about what Lumens are.

In the later part of my childhood – in the 1970s and 1980s – we had incandescent light-bulbs, and we knew that only a small part of the so-called light they emitted was in the visible part of the spectrum. We often used this light-bulb type, because we had no better alternative. We knew that the visible part of the emitted light might have been 15% or 10% of the consumed energy.

Granted, in Industrial or Commercial Lighting, there existed other types of fixtures, such as mercury-gas-discharge tubes, that excited a phosphor with ultraviolet light, so that the phosphor was made to fluoresce. Or in some cases simply – a gas-discharge tube, with a gas-mixture of a composition unknown to me.

But, when I go to buy light-bulbs today, as an adult, like all the other customers, I see Compact Fluorescent Light-Bulbs, as well as LEDs, the brightness of which is stated in Lumens. What I generally tend to find, is that light-bulbs of the fluorescent family, which are meant to be equivalent to the ~Old, 100W~ incandescents, tend to draw approximately 23W, and are stated on the packaging to produce about 1500 Lumens.

Lightbulbs of the LED family with the same equivalence, are stated to draw about 16W, and to produce about 1500 Lumens. I have actually found LEDs, which are stated to draw about 17W, and to produce 1600 Lumens of visible brightness, but which possess a visibly-larger base, from the other types.

If I could just hazard a guess, I’d say that one way to understand Lumens, is to start with the Watts of light in the visible part of the spectrum, and to multiply those by 100. What this would suggest, is that the most-efficient LEDs waste about 1W as heat, while then fluorescents still tend to waste a bit more energy, such as perhaps 8W – some of that in the form of UV light, making those approximately 65% efficient. But this would also mean, that the efficiency of modern LEDs is hard to improve upon. If the brightest variety only seem to produce 1W of waste heat, out of 16W or 17W consumed, it would make most sense to infer that in that range of efficiencies, the Wattage can be translated into Lumens quite easily. More Watts will simply produce more light, and fewer Watts will produce less light. In percentages, the LEDs would seem to have an efficiency of about 94%.

If we have a new light-bulb type, that draws 4.5W, but that produces visible light amounting to 350 Lumens, it would follow from this thinking, that this type is wasting about 1W / 4.5W. In percentages, this would imply an efficiency of 78%.

I suppose that I can offer a comment on the temperatures which the light-bulb-bases of household LEDs reach…

Continue reading I could make a loose inference, about what Lumens are.

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A Type Of Light-Bulb That’s New To Me

In the past, I’ve tended to categorize light sources something like this:

  • Incandescent,
  • Gas-Discharge Tube,
  • Fluorescent,
  • Phosphorescent,
  • Bioluminescent,
  • Electroluminescent,
  • LED (Semiconductive, Light-Emitting Diode).

But, there seems to be a light-bulb on the market right now, that defies this system of categorization, as shown here:

foxy_150409180629

The yellowish parts that emit the light will look something like decorative, low-temperature tungsten filaments when lit, but are not in fact filaments at all. They seem to be narrow, tubular, Electroluminescent parts of unknown composition.

What I find most striking about this design, is that it also does not have a power converter in the base, instead just applying the 110 VAC house-current directly to the apparently-electroluminescent material, with passive wires inside the bulb.

When trying to form some sort of guess, as to what the EL material could be, my attention goes next to the fact that by now, organic semiconductors exist. These types of semiconductive polymers are often the basis for OLEDs, also known as Organic Light Emitting Diodes.

With a true LED design, actual, electrical diodes need to exist, that operate at low voltages and correspondingly higher currents, and due to which, the light-bulbs have required power-converters in their base. Those power-converters would also be the main point of failure, that limits the lifespan of an LED light-bulb. Those power-converters have also tended to become quite hot in-use.

But because this type of light-bulb does not form an electrically-correct diode, I would not call this form an LED. What seems to have been done, is that some mixture of organic semiconductors has been pressed into a shape, and the house A/C applied directly to it. This means that they could potentially outlast more-conventional LED-light-bulbs, but should also have slightly lower energy-efficiency.

They look pretty when lit.

The packaging of this light-bulb made some statements which I do not believe to be entirely accurate.

  • The lightbulb-type is stated to be an LED,
  • It’s said to be equivalent to a 40W incandescent,
  • It’s said to have a life-expectancy of 9 years,
  • It’s stated to draw 4.5W of real power.

The only packaging-information above which I believe to be accurate, is the consumption of 4.5W.

( Last Updated 08/31/2017 … )

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Web-Optimizing Lossless Images

One subject which has caught my interest in recent times, is how to publish lossless images on the Web – and of course, optimize memory-use.

It has been a kind of default setting on most of my desktop software, that I’ll either save images as JPEGs – that are lossy but offer excellent file-sizes – or as PNG-Format files – that are losssless, but that still offer much better file-sizes than utterly uncompressed .BMP-Files would offer. Yet, I might one day want even smaller file-sizes than what PNGs can offer, yet preserve the crisp exactitude required in, say, schematics.

The ideal solution to this problem would be, to publish the Web-embedded content directly in SVG-Files, which preserve exact curves literally at any level of magnification. But there are essentially two reasons fw this may not generally be feasible:

  1. The images need to be sourced as vector-images, not raster-images. There is no reasonable way to convert rasters into vector-graphics.
  2. There may be a lack of browser-support for SVG specifically. I know that up-to-date Firefox browsers have it, but when publishing Web-content, some consideration needs to be given to older or less-CPU-intensive browsers.

And so there seems to be an alternative which has re-emerged, but which has long been forgotten in the history of the Web, because originally, the emphasis was on reducing the file-size of photos. That alternative seems to exist in GIF-Images. But there is a basic concern which needs to be observed, when using them: The images need to be palletized, before they can be turned into GIFs – which some apps do automatically for the user when prompted to produce a GIF.

What this means is, that while quality photos have a minimum pixel-depth of either 24 or 32 Bits-Per-Pixel (‘BPP’), implying 8 Bits Per Channel, and while this gives us quality images, the set of colors needs to be reduced to a much-smaller set, in order for GIFs actually to become smaller in file-size, than what PNG-Files already exemplify. While 8-bit-palletized colors are possible, that offer 1/255 colors, my main interest would be in the 4-bit or the 1-bit pallets, that either offer the so-called ‘Web-optimized’ standard set of 16 colors, or that just offer either white or black pixels. And my interest in this format is due to the fact that the published images in question are either truly schematic, or what I would call quasi-schematic, i.e. schematic with colors.

What this means for me as a writer, is that I must open the images in question in GIMP, and change the ‘Image -> Mode’ to the Web-optimized, or the 1-bit Pallets, before I can ‘Export To GIF’, and when I do this, I take care to choose ‘Interlaced GIF’, to help browsers deal with the memory-consumption best.

In the case of a true 1-bpp schematic, the effect is almost lossless, as the example shown below has already occurred elsewhere in my blog, but appears as sharp here as the former, PNG-formatted variety appeared:

schem-1_8

In the case of a quasi-schematic, there is noticeable loss in quality, due to the reduction in color-accuracy, but a considerable reduction in file-size. The lossless, PNG-format example is this:

quasi-schem-1_1

While the smaller, GIF-format File would be this:

quasi-schem-1_9

There is some mention that for larger, more-complex schematics, GIFs take up too much memory. But when the image really has been large in the past, regardless of what I might like, I’ve been switching to JPEGs anyway.

There could be some controversy, as to whether this can be referred to as lossless in any way.

The answer to that would be, that this results in either 1 or 4 bit-planes, and that the transmission of each bit-plane will be without alteration of any kind – i.e., lossless. But there will be the mentioned loss in color-accuracy, when converting the original pixel-values to the simplified colors – i.e. lossy.

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