Yuji VTC-series D50 5730-size midpower led tested

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djozz
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Yuji VTC-series D50 5730-size midpower led tested

Since I'm aware of Yuji leds I wanted to see for myself what that ultra-high CRI was looking like in reality. Especially their VTC series which is 98CRI and based on purple leds instead of blue (to get rid of the cyan dip in the output spectrum) fascinated me. But two reasons kept me from buying them: 1)the high shipping costs plus that they are sold per hundred pieces, and 2)they do not make high power leds so the output in a flashlight will always be underwhelming.

 

Now recently they started selling a new type of their VTC-series leds: the D50 (beta-)version, which has the same 98CRI but with the phosfors tweaked a bit to make them (partly) compliant to ISO3664:2009, which defines the D50 standard illuminant published by the CIE. A good enough reason or not, this was my tipping point for buying a batch of these.

 

So what is a standard illuminant? (I'm not more than slightly ahead of you, but I suspect that maukka is more educated than me in this). Wikipedia: A standard illuminant is a theoretical source of visible light with a profile (its spectral power distribution) which is published. Standard illuminants provide a basis for comparing images or colors recorded under different lighting.

 

And the D50 standard illuminant represents "horizon"daylight of 5000K (as opposed to i.e. "noon"daylight of 6500K). So scientists took numerous samples of horizon daylight and averaged the spectra into the D50 standard. This led is a close D50 illuminant but apparently not close enough to fully comply to the norm. Here's a graph comparing the spectrum of this led to the D50 spectrum (taken from the Yuji website, more data there):

 

The tested led is a 5730-size midpower led specified for 150mA and about 38 lumen. Not only the output is flashlight-unfriendly but also the led-shape, and tint-variation in the die will guarantee a less than ideal beam profile when used in a reflector light (although not worse than the XP-G3, I checked but made no picture):

A plus is that this led-size can be succesfully used on a standard XP-board. it works fine but the source of the light will be off-center a bit:

 

(the image on the right shows the led in a small zoomie that will be discussed below).

 

So how's the output? I did a test! As a habit I used a DTP-board for the test, but the thermal resitance of this low-power led is so high (23 degC/W) that the type of ledboard will unlikely be the bottleneck for thermal performance, any non-DTP board will probably give the same results.

The output test was done like all my more recent emitter tests. I described it in detail in my XP-L test. , with two minor differences that should not matter significantly for the results: I used my Integrating sphere no. II instead of no. I, and for the current I used a clamp meter, which appears to measure 0.1A lower than the power supply current-reading that I used before.

In summary: 1) just one led was tested, reflowed on a DTP copper board (KD-light 16mm) 2) I used my large version II integrating sphere with high quality luxmeter, 3) the output numbers and voltages were measured with the led close to 'steady state' for each current, so warmed up and settled, you should be able to get these numbers in a well heatsinked flashlight. Mind that these are output numbers of the bare led, in a flashlight there will be losses from light obstructions, lens and optic, 4) output is in 'djozz-lumen' defined as 1/550 of the output of my Sunwayman D40A on high setting, which I hope is close to the real lumen, but at least is consistent over all my emitter tests done in integrating spheres.

Here's the graph:

What can be seen?

*It is nice that the led can handle quite a bit more current than the specified 150mA, it runs it up to 300mA without problems, with 65% more output. The led was still alive at 600 mA.

*40 lumen at 150mA is also over specs, although my 'djozz-lumen' is still not officially calibrated to a standard light source.

*the voltage curve is quite steep, the led can even run succesfully direct drive on a li-ion battery although I would call that overdriven.

*as a light source in a flashlight, with losses by optics and light obstructions and such, it can provide a bit over 50 lumen maximum.

*300mA drive current is AAA-battery with boost driver territory Smile

 

So now what to do? I reckoned that i would make a little D50 flashlight with one of these leds, and the nature of this led made me decide to use a zoomie, to be able to evenly illuminate something in flood setting. Spot setting of course spoils any standard illumination with the ugly die projection. I used this über-cheap AAA-zoomie:

 

 

It has just 1 mode and runs on a standard AAA alkaline battery or AAA NiMh battery. I have not tried a 10440 li-ion in it yet, might kill it! I reflowed the Yuji-led on the tiny stock ledboard, re-shaped the plastic disc that presses the ledboard on its shelf to fit the odd-size led and extract a bit more light.

And it works fine, in flood a nice even illuminated circle of about 30 lumen, and the ugly die projection in spot. And the ultra-high CRI light that comes out is almost boring, so natural is the appearance Party

In all other aspects the performance is poor: for those 30 lumen, the Eneloop delivers 1.2A, which is an ultra-low system performance of 21 lumen/W (my most efficient lights are close to 120, with very low CRI of course). This is caused by the inefficient led, the fact that it is a zoomie, and the cheap boost driver eats a lot of power too.

I made a beamshot that compares the light to a flashlight with 83 CRI 5000K Nichia 219C leds and with my eyes I can see the difference well enough, but photo's (and here my phone camera is also to blame since UV-over-exposure damaged the center part of the imaging chip, leading to a slight colour deviation) are a very poor representation of what you see with your own eyes. Left 83 CRI Nichia, right Yuji D50.

Conclusion

So that was fun, to see and test one of these VTC-series leds. Hardly useful for flashlights but as you see you can make a weak light out of them (perhaps reflow 4 of them on a MT-G2 board will make it a bit more powerful). But I like the little flashlight that I made, the light it gives is really great and I will treasure it as something special. Btw, I bet this led fits that small and flexible IKEA USB-light too, or you can do some household ledbulb surgery and replace the leds in there.

 

I hope you liked reading this test Smile

___________________________________

 

Edit August 2017: in post #27, clemence describes a nice build with these leds, including tint pictures, and in post #29, maukka does his great tint and CRI analysis Smile

Edited by: djozz on 08/27/2017 - 05:08
djozz
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EDIT August 2017: I’m sold out, none left for sale.

For who’s interested, as I had to buy a hundred pieces of them, I have a bunch of these leds leftover (say 70). Shoot me a PM and I get them to you for about cost price (leds+shipping to me+shipping to you): they will be $1.20 a piece, plus an envelope and a stamp is an extra $1.50. To prevent me from sending out too many envelopes the minimum is 5 pieces. I hope there is some interest in them.

I also have some 5700K 95CRI 5mm leds from Yuji now, these are nice too, for $0.20 each (not including envelope plus stamp).

I have a very busy month ahead, so expect some delay in shipping them.

EasyB
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Interesting write-up. Thanks.

mattlward
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Dang, the tint and cri look amazing! I have 4 of their 5mm hi cri warm emitters, 2 in my magnified headlight and really like them. I would love to see them make a high power led.

EDC rotation:
FW1A, LH351D 4000k (second favorite)
FW3A, LH351D 3500k
FW3A, SST20 FD2 4000k
FW3A, Nichia 4000k sw40 r9080 (favorite light!)
FW3A, Cree XP-L Hi 5A3
Emisar D4V2, SST20 4000k
S2+, XM-L2 T6 4C

djozz
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mattlward wrote:
I would love to see them make a high power led.

They do make this one Innocent :
mattlward
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Ok… 5050 size!

EDC rotation:
FW1A, LH351D 4000k (second favorite)
FW3A, LH351D 3500k
FW3A, SST20 FD2 4000k
FW3A, Nichia 4000k sw40 r9080 (favorite light!)
FW3A, Cree XP-L Hi 5A3
Emisar D4V2, SST20 4000k
S2+, XM-L2 T6 4C

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When you mentioned you had to buy one hundred I thought to myself that you scored a couple for testing from the manufacturer. I laughed when I read the second post. You bought a hundred. Now that is taking one for the team. Your enthusiasm is commendable. Thanks for the testing.
If you get stuck with a heap of left over leds I’d be happy to donate a few bucks to you for the cause. Cheers.

 

djozz quotes, "it came with chinese lettering that is chinese to me".

                      "My man mousehole needs one too"

old4570 said "I'm not an expert , so don't suffer from any such technical restrictions".

Old-Lumens. Highly admired and cherished member of Budget Light Forum. 11.5.2011 - 20.12.16. RIP.

 

mattlward
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Those would make a great panel light.

EDC rotation:
FW1A, LH351D 4000k (second favorite)
FW3A, LH351D 3500k
FW3A, SST20 FD2 4000k
FW3A, Nichia 4000k sw40 r9080 (favorite light!)
FW3A, Cree XP-L Hi 5A3
Emisar D4V2, SST20 4000k
S2+, XM-L2 T6 4C

vulpes
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djozz wrote:
I also have some 5700K 95CRI 5mm leds from Yuji now, these are nice too, for $0.20 each (not including envelope plus stamp).

Would those be suitable replacement for Nitecore Tube?

djozz
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vulpes wrote:
djozz wrote:
I also have some 5700K 95CRI 5mm leds from Yuji now, these are nice too, for $0.20 each (not including envelope plus stamp).

Would those be suitable replacement for Nitecore Tube?


yes, no problem I guess, nice application!
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Nice test, djozz.

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Interested in 10 or 20 pieces.

I have some Osram high CRI of the same size, and when you use them without optics they’re really wide angled and no (hardly any) tintshift.
Great for a headlamp for close up stuff.

Question:
Is it noticeable that these little buddies have cyan in their spectrum?

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Cool

…a bit pricey though…

djozz
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Jerommel wrote:
Interested in 10 or 20 pieces.

I have some Osram high CRI of the same size, and when you use them without optics they’re really wide angled and no (hardly any) tintshift.
Great for a headlamp for close up stuff.

Question:
Is it noticeable that these little buddies have cyan in their spectrum?


10 or 20 pieces is ok.

I think they are great for a close-up headlamp. If you are in improvisation mode you can stick one of these

into one of these

and put that in one of these

You will not notice the cyan, we humans can not see narrow wavelength bands. There has been some discussion on CPF that high CRI leds are somewhat rosy because of the lack of this band and compensating the tint for that is in principle easy but that compromises the CRI.

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I would expect that cyan / turquoise coloured objects look more ‘vibrant’ when there’s also cyan in the light source spectrum.

(I’ll PM you shortly.)

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These seem great for retrofitting to a magnifying-type desk lamp.

I just did mine the past weekend, using some neutral white 4014 LEDs from Aliex. Nice improvement, the original 5 mm ‘straw-hat’ LEDs were horrible in comparison. The PCB is single-sided and made for through-hole LEDs, but flipping it over and flowing the LEDs to the through-hole pads was not too difficult. 40 LEDs at 20 mA give plenty of light in that setup with no heat.

Now I will have to redo it Smile

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Whoaaa, very nice colour! Now it’s violet die, next is purple (Seoul and Toshiba)
Thanks for testing Djozz!

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Hi I joined just to make this post.
They now have 10W COBs in stock, VTC! MOQ just 5.

I love this yuji VTC spectrum by the looks of it.
So I ordered 5 yesterday, Im verry curious!!

but ONLY 450mA?

The thing Im asking myself is, can you amp them up?

Not a lot of info around, no spec sheet..yet?
https://store.yujiintl.com/collections/vtc-series/products/vtc-series-hi...

But yeah I am thinking what driver to take, I want a higher current dimming model, so I can overdrive them, but how much?
How far should I go?

Im gonna use big ass heatsinks so…

Anybody any idea? max 700mA? 1050mA? 1400mA??

ciao
Rokus

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Just received mine yesterday. Will find a time to test them out. Thanks Jos =))

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clemence wrote:
Just received mine yesterday. Will find a time to test them out. Thanks Jos =))

Sounds like a plan!
Front row here

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Rokus wrote:
clemence wrote:
Just received mine yesterday. Will find a time to test them out. Thanks Jos =))

Sounds like a plan!
Front row here

Don’t expect quantitative tests like Djozz’s or Maukka’s. I will only use my camera, not the best valid test for comparing CRI, but it’s just fun thing to do.

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For me it has mainly to do with the max current that is safe to run them cool enough for longer periods on end.

450mA seems like a very low estimate to me!

https://store.yujiintl.com/collections/vtc-series/products/vtc-series-hi...

(Talking about the COBs here VTC Series High CRI COB LED – 135L)

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Rokus wrote:
For me it has mainly to do with the max current that is safe to run them cool enough for longer periods on end.

450mA seems like a very low estimate to me!

https://store.yujiintl.com/collections/vtc-series/products/vtc-series-hi...

(Talking about the COBs here VTC Series High CRI COB LED – 135L)

Keep in mind that generally leds will have degrading cri as they are pushed to their limits. There are s couple exceptions but to be guaranteed the rated cri, the rated current must be used. But this may not be a big deal for your purposes?

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Rokus wrote:
For me it has mainly to do with the max current that is safe to run them cool enough for longer periods on end.

450mA seems like a very low estimate to me!

https://store.yujiintl.com/collections/vtc-series/products/vtc-series-hi...

(Talking about the COBs here VTC Series High CRI COB LED – 135L)

Don’t judge only by the max current. COB usually have very high voltage to boost efficiency for AC powered LED light engines. Total power = Voltage x Current. For a rated 10 watt output, 450mA, translate into ~22-24Vf. And yes, specified CRI measured at manufacturer’s rated operating output.

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No light output is not really a big deal, although I was gonna light a bonsai plant under it in my livingroom. Now that you state it like that, it doesnt need to grow fast so it doesnt have to be super bright, just as long as the quality/efficiency surpasses my Truelight CFL!

http://docplayer.nl/3326979-5500-kelvin-true-light-volspectrum-daglichtl...

not entirely, but the violet is at least there, the form factor is and the spectum is nice and smooth.

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Good news!
Ted Bai from Yujileds just emailed me:

“Hi

I have attached the datasheet of VTC series 135L for your reference .

This is our latest datasheet and not yet been published .

You find all necessary information inside , including the maximum values .”

Yuji VTC 135L-G01

The bad news is, it is indeed low power. But that’s ok, its a beautiful product!

And the most beautiful if you run it exactly @ 450mA, because that’s where it’s calibrated at.

Mid power diodes, I heard someone shout, that’s where we’re going, small size and if you want a lot of light, put a lot of them together on a PCB.

https://store.yujiintl.com/collections/vtc-series

colour shifting from High to low K with 2 dimmers is also a very interesting option with these smashing spectra and boards. Of which the best, the one that looks like a quantum board, ofcourse is sold out lol, but those smaller boards mmmmm

Yuji VTC colormix

The violet spike is somewhat tempered in the new models btw, the gif shows the older spectrum..

Smile

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Finally, I have a very nice super high CRI Yuji floodlight.

The host used is a cheap Krisbow 10 watt floodlight bought from Ace Hardware store. Nothing worth to spare except the case and the driver. This outdoor floodlight has a sleek full cast aluminum body and low profile design. The glass cover is just a simple windows grade glass with sharp edges.

 

The original MCPCB installed with blob of thermal paste which wan't screwed down properly due to burrs in fixing holes. Total garbage. When I try to de-solder the LEDs off the board, it started to bubble below 220C. I always monitor my hot plate temp.

 

Found a broken 4 watt bulb, another Krisbow. Took the MCPCB, looked better. The LEDs were 5730 but the solder footprint is slightly different. A little scraping here and there and it fits the Yujis.

 

It's time to mod the case. Some drillings and M3x0,5 tappings. Swapped the MCPCB from the broken bulbs. Made two slots for screw fixing...

 

The Yujis installed. Not perfect due to footprint mismatch. I prioritized to align the cathode pads first. The broken path to anode connected with extra solder.

 

Soaked the finished board in IPA to clean the burnt flux. Tried to brush the brown residue but later changed my mind, too risky.

 

Applied the trusty MoS2 grease simply because I always forget to buy fancy thermal paste

 

This time the board is hard pressed against the case/heatsink.

 

Lapped the back of the glass cover using 320 grit silicone carbide powder to create slightly diffused lens. Looks good!

 

The driver outputs 9,45 watt to all 9 LEDs @290mA. About 11 watts total power consumed. The case got warm fast but still manageable under 46C (26C ambient).

 

Comparisons (ceiling bounced)

 

Thank you for the LED Jos. Now I have a super nice 5000K comparator light

- Clemence

 

EDIT: In hot sunny day (31C) and still air, the floodlight reached 35C hotter (66C). This worries me for long term continuous use. Need to find lower power supply and possibly better MCPCB. Next will be a fairer comparison to 5000K 9080 E21A

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Excellent mod work Clemence!

And nice 4500k and 4000k photos also!

(“It’s good that most people can’t remember their previous lives. Otherwise
things would be a lot more complicated than they already are.”
Ajaan Lee Dhammadharo)

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Just got one of these from djozz. I’d say it is quite a nice simulation for daylight.

Testing done at the rated current of 120mA (Vf was 3.48V)

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From what I understand about those graphs, that is really impressive.

I have heard that these LED’s can have high levels of UV radiation, what did you see in your testing?

I would not want to use them in a house if they are going to cause UV damage to everything in it over time for example.

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Texas_Ace wrote:
I have heard that these LED’s can have high levels of UV radiation, what did you see in your testing?

I would not want to use them in a house if they are going to cause UV damage to everything in it over time for example.

The relative UV output at 380nm is an order of magnitude higher than on normal Nichia or Cree emitters. But the X7R for example has as much UV content on low as the Yuji on its rated current.

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