NewBie
*Retired*
Billson said:
1000mA on that big monster heatsink above.
Seoul P4 initial Evaluation- Production LEDs
- Thread starter NewBie
- Start date
Help Support Candle Power Flashlight Forum
1000mA on that big monster heatsink above.
NewBie,
I have done my best to follow the thread, but I have missed a few comments, and didn't see your note on your hybrid integrating sphere.
My main point/question was the Other people are interpreting your data (again, thanks for providing it) to suggest that the Cree is producing nearly the same output as the Seoul, and I was commenting on the validity of this based on the different beam patterns (and test set-up).
So, my question is; from your data, can you make any reasonable guess as to the relative total lumen output between the Cree and Seoul chips you tested?
Thanks,
BPH
I have done my best to follow the thread, but I have missed a few comments, and didn't see your note on your hybrid integrating sphere.
My main point/question was the Other people are interpreting your data (again, thanks for providing it) to suggest that the Cree is producing nearly the same output as the Seoul, and I was commenting on the validity of this based on the different beam patterns (and test set-up).
So, my question is; from your data, can you make any reasonable guess as to the relative total lumen output between the Cree and Seoul chips you tested?
Thanks,
BPH
chimo
Flashlight Enthusiast
Seoul definitely has a different phosphor mix.
Here is a comparison with some Cree and Luxeons. The top photo is just taken in daylight. The bottom one was taken at the same time but has been illuminated by a 1W CreeUV light. I had to move the UV source a fair ways back so the Seoul phosphor would not saturate the image.
Paul
Here is a comparison with some Cree and Luxeons. The top photo is just taken in daylight. The bottom one was taken at the same time but has been illuminated by a 1W CreeUV light. I had to move the UV source a fair ways back so the Seoul phosphor would not saturate the image.
Paul
Newbie said:
If the tint shift is so noticiable, likely the output drop in lux reading is mostly due to it, meaning that about 1watt of radiometric power is emited, but with a luminous efficacy of 310 lm/w with the original tint, and 270 lm/w when it shifted.
If the shift is both to the blue and the red, the luminous efficacy may be easily higher than those 40lm/w. In contrast, the CRI should improve as consecuence. This trade off is very usual, but not in the same product. Glad you aware us, Newbie, really is something that SSC had to note. IMO, isnt a bad trade off, but the fact is P4's photometric efficiency is lower than announced when it reach a given (short) time use.
So there is a photometric output drop together with CRI improvement, but probably the radiometric output is somewhat stable. Impossible to say without a spectrometer, but if the tint shift is so noticiable, i believe that this analysis is reasonable. Of course, its impossible to say how much of the output drop is due to tint shift and how much of radiometric output degradation.
Personally, i like that kynd of tint (purplish), so im interested in this phospor for home use. Definitively, id like to know more about it. For me the main problem with the P4 is the gummy dome. IMHO, it make it just a good choice for enclosed lights.
BHP said:
As far as i can see it, it was already done along the thread. Newbie has explained in the last post why he cant get more accuracy than he had already showed. With this limitation in mind, the graph in the last Newbie's post show the relative emission (refered to watts consumed instead of current drawed, wich is more accurate than anything).
We are in the same boat
. If you find it, please tell me :laughing: . For the coating, i suggest you a 50/50 mix (by weight) of latex flat white paint and BaSO4 (Barium sulphate) (adding a bit of water make the mix more manegeable, its very dense). It had a pure lambertian reflection and excelent reflectance between 430 and 800nm. In most of the visible range, its just about 2% less than spectralon. The white paint only degrades reflectivity at 430nm or lower, and current blue/white chips emits very little in that range. From 430 to 700nm, differential reflectivity is very small, ranging from 96 to 98%.I'll try again (and then stop bothering you'll). I don't think I was able to make myself clear.
Can a reasonable conclusion be drawn from NewBie's testing as to if the Cree or Seoul has more Total lumen output? (that would be either yes or no)
I assume the answer is not really, too close to call. It could go either way depending on how NewBie's hybrid integrating sphere favors the particular radiation pattern of the emitter and other testing details.
-BPH
Can a reasonable conclusion be drawn from NewBie's testing as to if the Cree or Seoul has more Total lumen output? (that would be either yes or no)
I assume the answer is not really, too close to call. It could go either way depending on how NewBie's hybrid integrating sphere favors the particular radiation pattern of the emitter and other testing details.
-BPH
Calina
Enlightened
chimo said:
Wow, it glows
! Does this means that GITD buttons and O'rings are unnecessary with these lights?
Last edited:
chimo
Flashlight Enthusiast
Calina said:Wow, it glows
It doesn't stay glowing. The phosphor is being excited by a UV light I was shining on them. It glows a lot brighter than the other phosphors.
NewBie
*Retired*
BPH said:
With the parts I've managed to get my hands on, I'd tend to believe the Seoul P4 is a tad more efficient, once you look at Watts consumed, at least when it is new.
One of the falacies is that I've seen, folks pick a bottom binned P2 CREE, and then snag a nice U bin Seoul, and claim smackdown. Thats like picking an R binned Luxeon III and a U bin Seoul P4- of course, they are from different bins, quite obviously one will be a lot more efficient.
Some folks are attempting to measure accurate lumens with a typical light meter. Differences in color bins can cause considerable errors, and lead to erronous results. Even differences in spectral output between different phosphors can add error.
This would be considered a very high end photodiode, that has a much better color filter on it than one finds in many light meters:
http://www.vishay.com/docs/81519/81519.pdf
At the bottom of page 3, figure 5, you will see Vlambda eye-this is the human eye response. The black line is the actual photodiode, and it's response curve to light. Notice the large margin of error vs. wavelength for this part, when compared to the human eye. This where large errors can creep in.
I've seen folks compare an LED mounted on a MCPCB to one direct mounted on a copper plate. When you compare in this fashion, obviously the MCPCB will measure a tad lower, especially with the higher profit margin MCPCBs. To be fair, it is best to give them an equal thermal solution.
Power is what the LED is going to use in a flashlight, so you really want to look at Power, which is Volts * Amps. Current only can be rather misleading.
Besides shifting color in a relatively short time, and the loss of lumens, the Seoul P4 LEDs I've tested, also shift more in color with changes temperature than most white LEDs I've tested.
Some folks like to claim that this LED is worst, best, or whatever. Nothing wrong with the LED, it is just different, and different trade-offs were made in it's design as compared to other LEDs. Some of the trade-offs will be a positive thing, and some will be a negative thing. It all depends upon your goals, application, and such. It is nice to have a variety of choices for power LEDs these days.
Last edited:
wojtek_pl
Enlightened
I wonder if tint change would happen so fast with less amperage... Say 750 mA...NewBie said:
In general... this doesn't look good as reliability goes...
NewBie
*Retired*
The tint shift should be less with less current over time, but this is not something I've tested.
One of the large factors for tint shift over time is the die temperature, and it's affect on the phosphor. As I recall, the LED slug is held below 30C, the exact number should be mentioned earlier in the thread. This part has been held rather cool, due to the excessive heatsinking, and the thermal resistance to the LED die is very low in this part, so I doubt that is much of a contributor for this LED.
The datasheet cautions about the shift, but does not give an actual specific cause for it.
One of the large factors for tint shift over time is the die temperature, and it's affect on the phosphor. As I recall, the LED slug is held below 30C, the exact number should be mentioned earlier in the thread. This part has been held rather cool, due to the excessive heatsinking, and the thermal resistance to the LED die is very low in this part, so I doubt that is much of a contributor for this LED.
The datasheet cautions about the shift, but does not give an actual specific cause for it.
Measurements with tint errors:
I am most interested in doing field pattern tests on completely assembled systems. So I will be testing lux (lumens/sq.meter). There seems to be some good Spectral Response filters out there on ExTech light meters. I am looking at purchasing either the EA31 or EA33, unfortunately, neither has a PC connection but otherwise they look good. Here is page from their pdf;
I am most interested in doing field pattern tests on completely assembled systems. So I will be testing lux (lumens/sq.meter). There seems to be some good Spectral Response filters out there on ExTech light meters. I am looking at purchasing either the EA31 or EA33, unfortunately, neither has a PC connection but otherwise they look good. Here is page from their pdf;
NewBie
*Retired*
I didn't notice Extech's new meters have a "precision" sensor and filter.
Very nice BPH!
Now all we need is a model that has this sensor in it, plus a PC hook-up.
Very nice BPH!
Now all we need is a model that has this sensor in it, plus a PC hook-up.
NewBie
*Retired*
I did some spectral scans of the Seoul P4 and CREE XR-E @ 700mA:
Un-marked up:
Both devices were new at the time of testing. You'll note the different phosphor response of the two LEDs. The Seoul has more yellow, significantly less "cyan-green", and slightly less red. The blue is slightly deeper on the Seoul, but this spot moves around a bit from part to part, depending on the die. The eye has difficulty noting wavelength differences at 460-470nm range anyhow.
Over temperature, @ 750mA, the majority of the color shift occurs when the slug temperature goes above 40C:
Un-marked up:
Both devices were new at the time of testing. You'll note the different phosphor response of the two LEDs. The Seoul has more yellow, significantly less "cyan-green", and slightly less red. The blue is slightly deeper on the Seoul, but this spot moves around a bit from part to part, depending on the die. The eye has difficulty noting wavelength differences at 460-470nm range anyhow.
Over temperature, @ 750mA, the majority of the color shift occurs when the slug temperature goes above 40C:
Last edited:
Nereus
Enlightened
Newbie, thanks again for excellent info! I have some questions about your newest graphs:
- Seoul seems to have deeper valleys and higher peaks in its spectral distribution than Cree. Does this mean that Cree has better CRI?
- I have always wondered how an earth Seoul can be slightly more efficient than Cree even though they use exactly the same die. Could it be that Seoul has traded some CRI to efficiency?
- I have understood that overdriving makes white leds more blue because under OD there is "too much" blue light for phosphor to be transformed to other colours. However, your graph tells me that there might be thermal issues as well: when OD heats the phosphor up, its ability to transform blue to other colors suffer. Am I right?
Thanks!
-N
- Seoul seems to have deeper valleys and higher peaks in its spectral distribution than Cree. Does this mean that Cree has better CRI?
- I have always wondered how an earth Seoul can be slightly more efficient than Cree even though they use exactly the same die. Could it be that Seoul has traded some CRI to efficiency?
- I have understood that overdriving makes white leds more blue because under OD there is "too much" blue light for phosphor to be transformed to other colours. However, your graph tells me that there might be thermal issues as well: when OD heats the phosphor up, its ability to transform blue to other colors suffer. Am I right?
Thanks!
-N
NewBie
*Retired*
I do not know what their intentions are.
Apparently this higher efficiency phosphor doesn't hold up as long, and is more temperature sensitive. The datasheet also has a warning about how the part shifts a bunch towards the blue in the first 1000 hours.
If you look at jtr1962's white lumen testing thread, you will see the Cree P4 bin nearly matches the Seoul P4 U bin. Where everyone got astray, is that they were looking at a bottom end bin XR-E P2 bin and comparing it with a top end Seoul P4 U bin. Do the comparisions yourself:
http://candlepowerforums.com/vb/showpost.php?p=1858937&postcount=116
Apparently this higher efficiency phosphor doesn't hold up as long, and is more temperature sensitive. The datasheet also has a warning about how the part shifts a bunch towards the blue in the first 1000 hours.
If you look at jtr1962's white lumen testing thread, you will see the Cree P4 bin nearly matches the Seoul P4 U bin. Where everyone got astray, is that they were looking at a bottom end bin XR-E P2 bin and comparing it with a top end Seoul P4 U bin. Do the comparisions yourself:
http://candlepowerforums.com/vb/showpost.php?p=1858937&postcount=116
Led_Blind
Enlightened
Howdie.... Remember the Lux's having the die cup loose its plating? I think the seul leds have the same behaviour...
I have a HDS modded with P4 since the first Seuls came available (2 months??). Being a true flashaholic i have runt this light as the bedroom light (on max) for one full 18650 almost every night (2-3 hrs)
Now looking at the led, the area around the phosphor coat has gone all coppery. Has any one noticed this?
I have a HDS modded with P4 since the first Seuls came available (2 months??). Being a true flashaholic i have runt this light as the bedroom light (on max) for one full 18650 almost every night (2-3 hrs)
Now looking at the led, the area around the phosphor coat has gone all coppery. Has any one noticed this?
