LED Bulbs

Just to expand about the module quality vs. price.

Take a look at this Bridgelux module (no, i'm not a salesperson from them, it's just that this is stuff i actually used myself). It has 30.3V at nominal 1.5 Amperes, giving you about 45 Watts.

Now this module costs roughly 23 US$. And this is _only: for the module. One would still need a suitable constant current supply, a suitable enclosure, heatsink, etc. But these modules do what is claimed they do. A hell lot of light, realiably.

Compare that to a 5 US$ chinese firecracker made of hundreds of single 5mm LED's, allegedly giving you 40 Watts.... And that is _with_ enclosure, etc.

I guess you can see where i'm going with this....

Greetings,

Chris
 
tuxcat said:
How does a LED compare to a normal lightbulb insofar as brightness and colour temperature? I'm considering getting some.
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Brightness to power ratio: Nearly ten times better than old-fashioned bulbs. Some eight times better than halogens.

Color temperature: Well, you can usually choose between different ones.

Spectrum coverage: Pretty good. Much better than flouroscent lamps. There is a small gap in the blue range but otherwise, a nice, continuous spectrum.

Price: Well, much more expensive, but you will recover the purchage price in about half the lifetime of an old bulb, due to the power saving, and after that it will live some ten times longer.

They are an excellent investment.

Hans
 
As a side note:

It also is worthwhile to reconsider how you install the lighting in your home, when using LED's. After all, LED light bulbs that fir in regular sockets are more of an compromise, to make the switch-over easy. But they are far from optimal when it comes to really useing the benefits of LED's.

Those bulbs (and by extension, high powered LED modules like the one i mentioned) are meant to produce a lot of a light in a single place, in the hope it spreads out into whatever you are going to illuminate. But there are rather easy to implemet options, if you are willing to depart from that philosophy.

Just as a quick example, if you have rudimentray skills to build your own stuff. Use L or U shaped profiles, thin ones. Mount them on your walls, a few cm below your ceiling. Then place flat LED strips in them, shining upwards to your ceiling. The profile is there so you never look directly into the bright LED's. That way you get a nice, indirect lighting in your room.

There is virtually no way to do that nicely with incadescent lamos, due to the heat. Even fluorescent tubes are limited here, because they are rather thick and need a bulky ballast to operate. With LED's you can make that virtually invisible. If you are into electronics (or get the proper constant-current supply) you can make it dimmable.

And heck, you don't even need to use white LED strips for that. Use RGB LED strips. They cost a bit more, but that way you can add some nice colour to your ambient lighting.

Really, i think that traditional lighting concepts are not really suitable for LED lighting. Not because they wouldn't work, they do, but because those traditional concepts are limited by the physics of regular bulbs (= heat, big size and high current consumption in low voltage applications). LED's allow _much_ more freedom in the way you arrange them.

My hope is that some day organic LED's will have a better lifetime expectancy and become cheaper. With that technology you can literally have your wallpaper _be_ the light source instead of just reflecting light from some other source. But i guess that will be quite a long way to come...

Greetings,

Chris
 
I've seen a bit of coverage of this but I'd like to ask specifically. What is the light like visually?

I personally don't like tube florescent lights, I find their light too harsh. It's not a brightness thing, it's the actual bluish-white color of the light that I find unpleasant. Also they make that horrible high pitched whine. However I have found that many of the more recent florescent bulbs are actually quite nice, I think they may be coated with something that makes the light seem yellower. Old fashioned light-bulbs are a nice golden yellow but tend to be pretty dim.

So, what are these LED Bulbs like? Are there different coatings that I should be aware of? Also, can they work in a dimmer switch?
 
Weak Kitten said:
I've seen a bit of coverage of this but I'd like to ask specifically. What is the light like visually?

I personally don't like tube florescent lights, I find their light too harsh. It's not a brightness thing, it's the actual bluish-white color of the light that I find unpleasant. Also they make that horrible high pitched whine. However I have found that many of the more recent florescent bulbs are actually quite nice, I think they may be coated with something that makes the light seem yellower. Old fashioned light-bulbs are a nice golden yellow but tend to be pretty dim.

So, what are these LED Bulbs like? Are there different coatings that I should be aware of? Also, can they work in a dimmer switch?
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I have Philips "soft white" bulbs in most areas of the house. It's pretty indistinguishable to standard incandescent bulbs. Maybe not as yellow but I'm perfectly happy with them.

The only thing I ever notice is the 0.25 second delay from when I hit the light switch to when the bulb lights up (and it lights up at full brightness, no warm up period).
 
Weak Kitten said:
I've seen a bit of coverage of this but I'd like to ask specifically. What is the light like visually?

I personally don't like tube florescent lights, I find their light too harsh. It's not a brightness thing, it's the actual bluish-white color of the light that I find unpleasant. Also they make that horrible high pitched whine. However I have found that many of the more recent florescent bulbs are actually quite nice, I think they may be coated with something that makes the light seem yellower. Old fashioned light-bulbs are a nice golden yellow but tend to be pretty dim.

So, what are these LED Bulbs like? Are there different coatings that I should be aware of? Also, can they work in a dimmer switch?
Click to expand...

As for the light they produce, you really have to check the bulb you want to use. Again, cheap ones are usually "harsh", better ones are softer. Basically, fluoros and white LED's use the same principle: blue or UV light is produced by the lamp itself, and it then gets converted into white light by a special coating. However, LED's (at least the better modules) have the advantage that this partical, re-emitting coating itself has some colouring (usually in the yellow-ish) that improves the spectrum of the light.

Generally, there is cold-white white, and warm-white. For stuff were you work, like your desk or kitchen top, it is better to use cold-white or white, for stuff like living rooms better use a warm-white type. But then, it also depends on what you prefer, of course.

Regarding a dimmer, usually they don't work with that, same as for simple CFL's. However, there are many types that do work in such a setup. But then, as i mentioned in y previous post, you may also want to reconsider _how_ you want to illuminate something. LED's offer _far_ more ways to do things. Try to get rid of thinking to use them like regular light bulbs. And with such systems you usually have no problem with dimming them (although you usually need a different controller to do so, but often that is integrated in the current supply then).

Greetings,

Chris
 
kajata said:
The only thing I ever notice is the 0.25 second delay from when I hit the light switch to when the bulb lights up (and it lights up at full brightness, no warm up period).
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Sounds like you got a good one then. Some startup time indicates a good switchmode supply. A longer startup time _may_ indicate that the bulb is also dimmable (due to the way such a thing is implemented usually). Is it?

However (for the others), this is no indication at all as to the overall quality. It is also possible to have a switchmode supply that starts up virtually instantly, pretty much indistinguishable from a cheap resistor...

Greetings,

Chris
 
Brian-M said:
I've tried that, it gave the globe a marginally perceptible but still annoying 50Hz flicker.

I suspect a commercial device would have used a triac instead of a diode. No flicker and no DC bias on the mains.
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Well, it's possible I guess. We have 60 Hz power in the US. I have never tried one, but that could make a difference. Every half cycle is close to the flicker threshold even though the incandescent persistence is a large mitigating factor.

ETA: Apparently there were some devices that used a thermistor, and also a claim that an SCR was used in prior art, though I can't imagine why. Triac, I can see why.

A thermistor is a device made of a material that has a relatively high resistance when cold, and when heated by inrush current and voltage drop losses (I2R), its resistance goes down.

However, here is a patent for a device that seems to propose using just an axial series diode.

....which article includes a standard, conventionally packaged, power decreasing and/or transient limiting device, such as an axial lead diode, for decreasing by a factor of approximately two and for limiting the turn-on and turn-off transients from the power input to a filament light bulb inserted into the socket.
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Olowkow said:
ETA: Apparently there were some devices that used a thermistor, and also a claim that an SCR was used in prior art, though I can't imagine why. Triac, I can see why.
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Well, the first "device" to increase the lifespan of incadescent bulbs that i know of was just a diode in series. Meaning that you get just one half wave of the line voltage. An SCR is just a diode with a controlling gate, so to say. If you want to use half a cycle only anyways, a TRIAC doesn't make much sense. But then, a SCR is too much there already. I gues it has to do with reimplementing old patents and selling them as "new" without violating said old patents.

Also, as far as German nomenclature is concerned, the term "Thermistor" is more generally used for heat dependant resistors that work both ways. That is, you can have a "Heißleiter" (resistance lowers the hotter it gets) or a "Kaltleiter" (resistance lowers the colder it gets). The latter ones often used in the degaussing circuitry of old CRT monitors.

Greetings,

Chris

Greetings,

Chris
 
Weak Kitten said:
I personally don't like tube florescent lights, I find their light too harsh. It's not a brightness thing, it's the actual bluish-white color of the light that I find unpleasant. Also they make that horrible high pitched whine. However I have found that many of the more recent florescent bulbs are actually quite nice, I think they may be coated with something that makes the light seem yellower. Old fashioned light-bulbs are a nice golden yellow but tend to be pretty dim.
Click to expand...

I think the "horrible high pitched whine" complaint could only be caused by a low-quality electronic ballast. Old-fashioned wire-wound ballasts would only be able to make a low pitched hum, but a good ballast shouldn't make any noise whether it's electronic or wire-wound.

As for the light, I think what you're talking about is color temperature.

2700 K - Warm White Standard incandescent light-bulbs.
4100 K - Cool White Common color for fluorescent tubes.
6500 K - Daylight A bluish-white that imitates the color of sunlight.

The names I've given these colors are approximate. For example, the color temperature 5000 K is sometimes described as "Cool White" and sometimes described as "Daylight" depending on the manufacturer.

Personally, I use compact fluorescent bulbs that produce Warm White light for most of my home, to mimic the color of incandescent bulbs. You can get CF bulbs that produce any kind of light, it's only a question of what mixture of phosphor is applied to the inside of the tube.

The same goes for LED lights, they come with a variety of different color temperatures too, depending on the phosphor used. Make sure you check what the color-temperature of the bulb is before you buy it.
 
Christian Klippel said:
Well, the first "device" to increase the lifespan of incadescent bulbs that i know of was just a diode in series. Meaning that you get just one half wave of the line voltage. An SCR is just a diode with a controlling gate, so to say. If you want to use half a cycle only anyways, a TRIAC doesn't make much sense. But then, a SCR is too much there already. I gues it has to do with reimplementing old patents and selling them as "new" without violating said old patents.

Also, as far as German nomenclature is concerned, the term "Thermistor" is more generally used for heat dependant resistors that work both ways. That is, you can have a "Heißleiter" (resistance lowers the hotter it gets) or a "Kaltleiter" (resistance lowers the colder it gets). The latter ones often used in the degaussing circuitry of old CRT monitors.

Greetings,

Chris

Greetings,

Chris
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I agree with all of that. In my experience, a "thermistor" was usually a small device with known temperature vs. resistance characteristics that was used as a temperature measuring element. A common one is a platinum TDR with a 20C resistance of 100 ohms ( temperature dependent resistor, or thermistor) but the tiny ones, size of the head of a pin, were much cheaper. One use was to sense heat and turn on a transistor to drive a cooling fan. I never bothered to find out what was in them.

In switching power supplies and high power Rf amplifiers a two lead element that looked like a surge protector, but was black, was used to limit inrush current to reasonable values so the fuse would not blow. These were also called "thermistors". And yes, different types of thermistors can have either positive or negative temperature coefficient.
 
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I'm decided on LED bulbs. I'll try and find an Edison E14 screw one for my bedside lamp (I read a lot so it's on for a long time) and read the reviews beforehand. Phillips is a trusted brand in the UK - there are a lot of unbranded ones on Amazon and needless to say I'm steering clear of them!
 
I have had CFL's in ceiling track fixtures in the kitchen for years. My wife complains that there is not enough light for cooking. I just got back from spending $88.00 on LED bulbs, some floods and some small floods, and 1 bulb looking one.

We installed them in the kitchen. All are "daylight" types. All I can say is "wow". What an improvement! Sensational! All were Phillips, on sale at Home Depot.

I also bought an X-Box kinect. :D Why not?

I may get lucky tonight!:)
 
Weak Kitten said:
I've seen a bit of coverage of this but I'd like to ask specifically. What is the light like visually?

I personally don't like tube florescent lights, I find their light too harsh. It's not a brightness thing, it's the actual bluish-white color of the light that I find unpleasant. Also they make that horrible high pitched whine. However I have found that many of the more recent florescent bulbs are actually quite nice, I think they may be coated with something that makes the light seem yellower. Old fashioned light-bulbs are a nice golden yellow but tend to be pretty dim.

So, what are these LED Bulbs like? Are there different coatings that I should be aware of? Also, can they work in a dimmer switch?
Click to expand...

OK, here are the spectra (taken with a CD spectrometer, Google it to find how to build one, you need an old CD and a cardboard box).

As you can see, the incandescent has a nice, continuous spectrum, the LED misses some indigo and deep violet, but the flouroscent has deep gaps through all of the spectrum.

Note that this is true regardless of apparant tone: The tone is achieved by varying the strength of different parts of the spectum, but even the early harsh bluish "white" LEDs have a good spectrum.
 

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For your last questions:

The color is not in a coating, but in the balance beween different parts of the spectrum. Actually, you can buy LED lamps where you can adjust the color with a remote control.

Some are dim-able, others not. If it doesn't say "Dimable" on the package, they're probably not.

Hans
 
Olowkow said:
I have had CFL's in ceiling track fixtures in the kitchen for years. My wife complains that there is not enough light for cooking. I just got back from spending $88.00 on LED bulbs, some floods and some small floods, and 1 bulb looking one.

We installed them in the kitchen. All are "daylight" types. All I can say is "wow". What an improvement! Sensational! All were Phillips, on sale at Home Depot.

I also bought an X-Box kinect. :D Why not?

I may get lucky tonight!:)
Click to expand...

Philips LED lamps seem to be of fine quality. And in the top end of the price scale. I also prefer them.

Hans
 
Oh, and the reason these spectra are important:

You can fool the eye to recognize white light with as little as two colors (old B/W TV tubes did that), but when the light is reflected from a colored surface, the color is distorted because only the colors actually present in the light are represented.

Hans
 
MRC_Hans said:
Oh, and the reason these spectra are important:

You can fool the eye to recognize white light with as little as two colors (old B/W TV tubes did that), but when the light is reflected from a colored surface, the color is distorted because only the colors actually present in the light are represented.

Hans
Click to expand...

This is often overlooked and is quite important. You can have two illuminants that have exactly the same color temperature and purple/green hue offset or deviation from a black body but produce wildly different results when illuminating a colored object such as a photograph. There are techniques used in print processes to correct for this when a print is going to be located where these illuminants are used.

LEDs are not as spectrally spikey but still have some problems. Many of them have CRIs around 80 while some of the better fluorescents have CRIs as high as 90. CFLs typically have lower CRIs than LEDs though.
 
MRC_Hans said:
OK, here are the spectra (taken with a CD spectrometer, Google it to find how to build one, you need an old CD and a cardboard box).

<snip>
Click to expand...

Thanks, I never saw that CD spectrometer idea before, though it's obviously an ideal cheap diffraction grating/monochromator.
 
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