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Author Topic: LEDS for String LED Blades - What's the difference?  (Read 3801 times)

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Offline Ridire Fíréan

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LEDS for String LED Blades - What's the difference?
« on: January 08, 2017, 11:14:12 AM »
Hey Gang!  I've been reading up on LED-String LEDs and I'm getting confused.

As I've looked up LEDS on DigiKey and Mouser, I've noticed that there is a huge disparity in both price and mcd (microcandelas/millicandelas).

So, the first question I have is this: Does viewing angle effect the the brightness rating?  I would assume there is some sort of light measuring device for this and if the LED is pointed at it, it makes sense that the mcd rating would be higher on tighter light outputing viewing angles.  And conversly, that wide angle LEDS would have lower mcd's because their light is being directed out the sides and not out the top.  Is this correct?  Or does it have to do with how the LED is constructed internally or materials used?

If I took a dome topped LED with an 11000mcd rating, and drilled off its top to make it resemble a wide angle concave LED, would it be brighter than if I had just started off with a commercially available 6000mcd wide angle LED?

Some LEDs are sold for as little as $0.21 and some for $1.60.  Some of the $0.21 LEDS have higher mcd's than the $1.60 ones?  So, what's the difference in price?


Offline Sincenatic

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Re: LEDS for String LED Blades - What's the difference?
« Reply #1 on: January 08, 2017, 01:01:00 PM »
There is a formula if you would like to compare the LEDs in lumens instead of mcd. See for example, LED mcd (millicandela) to Lumens Converter . This makes it easier to compare LEDs in general terms, but it is important to remember that the viewing angle matters because of the technique we use for the string.

I am also curious about the question about if drilling out is better than buying a LED with already wide viewing angle. The problem is that most of us do not have equipment to actually test how bright they become. It is more trying and judging. My intuition is that LEDs made to spread the light more would be better than a home-made adjustment to achieve it. An argument to actually drill or sand the LEDs is when the particular color is unavailable with a wide viewing angle.

With higher price I would expect better quality; for example, all LEDs are from the same batch, with very similar color tone, brightness, viewing angle etc. I have never tried the most expensive LEDs and I have found that very cheap LEDs can also work very well. This is, of course, a risky recommendation and I guess there are a lot of unlucky examples in the other direction. My rule of thumb is to never buy anything that is labeled “superbright” when there are no information on mcd and viewing angle. If this information is available, it is, of course an issue if the information is accurate or not. A simple LED tester is also useful to sort out those LEDs with less “glow”. My feeling is that very cheap LEDs have very poor reputation, but this reputation may have been based on the quality found several years ago.

Offline Ridire Fíréan

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Re: LEDS for String LED Blades - What's the difference?
« Reply #2 on: January 08, 2017, 02:28:53 PM »
Hey Sincenatic, Weirdly, the $0.21 LEDS at Digikey and Mouser are binned CREE LEDS at 11000mcd!  I'm wondering if they aren't simply trying to kill off the competition by undercutting the price?

Offline jbkuma

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Re: LEDS for String LED Blades - What's the difference?
« Reply #3 on: January 08, 2017, 08:55:58 PM »
What are power demand specs on those?

Offline Ridire Fíréan

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Re: LEDS for String LED Blades - What's the difference?
« Reply #4 on: January 09, 2017, 06:51:18 AM »
Hey jbkuma,

If = Forward Current: 20 mA,  Vf = Forward Voltage: 3.2 V, Maximum Rating 4.0 V on all 3 of these examples.

This one is $0.21...
http://www.mouser.com/ProductDetail/Cree-Inc/C503B-BAN-CY0C0461/?qs=sGAEpiMZZMtmwHDZQCdlqaMeoG0BP2Kz8n5Xt%2f7pE7c%3d

This one is $0.22...
http://www.mouser.com/ProductDetail/Cree-Inc/C503B-BAN-CY0Z0452/?qs=sGAEpiMZZMtmwHDZQCdlqaMeoG0BP2KzXJ9UFBsFTR8%3d

They're different bins, the C0461 isn't on the data sheet, but the Z0452 is, so I don't know which one is brighter per CREE specs, but the Mouser specs have them exactly the same.  GO FIGURE!

This bad boy has 19380 mcd and is a WHOPPING $0.27!  WOO-HOO!!!...
http://www.digikey.com/product-detail/en/cree-inc/C503B-BAS-CY0C0461/C503B-BAS-CY0C0461-ND/1922943

Offline Ridire Fíréan

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Re: LEDS for String LED Blades - What's the difference?
« Reply #5 on: January 09, 2017, 07:36:53 AM »
Here's another that claims: "It has a diode within the LED that is designed for wide angle dispersion along with a "molded" concave lens that helps disperse light. The combination of these two things creates a wide angle LED that is unparalleled. This means that the light is more spread out and not so direct."

http://lighthouseleds.com/5mm-flat-top-concave-led-blue-ultra-bright-christmas.html

$0.19 and

Size    5mm Flat Top Concave LED
Color    Blue
Luminosity/Brightness    6,000-8,000 mcd
Forward Voltage    3.0-3.4v
Current    20mA
Wavelength    460-465nm
Viewing Angle    150-180 Degrees
Mount Style    Through Hole (DIP)
Lens Color    Clear
LED Brightness Class    Super/Ultra/Extreme

So, if the diode internals can truly be constructed to aide in light dispersion, then that's a whole other parameter to consider!

Offline Sincenatic

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Re: LEDS for String LED Blades - What's the difference?
« Reply #6 on: January 09, 2017, 09:08:29 AM »
I have tried the following LEDs, and below I use the mcd to lm converter to compare them:

5mm, Green 16000mcd, 40 degrees, -> 6 lm. (for 0.23€ when buying more than 250)
5mm, Red 4000mcd, 60 degrees, -> 3.4 lm. (for 0.30€ when buying more than 100)

The string built from the green LEDs is very bright and visually brighter than the string built from the red LEDs. These were made with a single string. I have also used the following, but in that case I use 4 LEDs in a set (which is explained at: Mixing colors in a string blade using four strings. ).

3mm, Blue 5000-6000mcd, 120-140 degrees -> 20 lm (at 0.06€ when buying 100).
3mm, Green 12000-14000mcd, 120-140 degrees -> 47 lm (at 0.06€ when buying 100).
3mm, White 16000-20000mcd, 120-140 degrees -> 65 lm (at 0.06€ when buying 100).

These are very cheap, and I doubt that the specifications are correct. They are still very bright but 47lm or 65lm cannot be true. For my set-up these works very well. Two strings of these would definitely work fine for someone that is not interested in mixing colors.

Among those that you show, I would recommend the one with wider viewing angle. The examples with only 15 degrees of viewing angle would require drilling or sanding them, and measured in lm they are still less bright.

Offline Ridire Fíréan

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Re: LEDS for String LED Blades - What's the difference?
« Reply #7 on: February 04, 2017, 12:46:03 PM »
O.K. so I bought 9 different LEDs (5 of each kind) in various mcd, viewing angles and lens configurations to test out which LEDS were brightest and to see what nm color I liked the best.  I got them all plugged in on my new breadboard last night after it arrived and took a few photos to see how the LEDs looked through the camera.

Here are the contestants (In order on the breadboard Top Left to Right, then Bottom Left to Right):

TOP ROW L->R
SuperbrightLEDS.com
    # RL5-B08-360       
        Voltage:                3.2Vf max - 3.0Vf typical
        Current:                100ma peak, 20ma test
        Viewing Angle:      360*
        Color:                   462nm Blue
        Millicandela:         100mcd

Digikey.com
    #365-1185-ND
        Voltage:                3.2Vf
        Current:                20ma
        Viewing Angle:      8*
        Color:                   505nm Blue-Green (thought this meant Cyan, NOPE! Totally GREEN!)
        Millicandela:         23,000mcd

    #C503B-BAN-CY0C0461-ND
        Voltage:                3.2Vf
        Current:                20ma
        Viewing Angle:      8*
        Color:                   470nm Blue
        Millicandela:         19,380mcd

    #CB503-BCN-CV0Z0461-ND
        Voltage:                3.2Vf
        Current:                20ma
        Viewing Angle:      30*
        Color:                   470nm Blue
        Millicandela:          7,065mcd

    #VA0L-5701SBY4-ND
        Voltage:                3.5Vf
        Current:                20ma
        Viewing Angle:      100*
        Color:                   470nm Blue
        Millicandela:          1,000mcd

BOTTOM ROW L->R
LighthouseLEDs.com
    #5MMFLATTOPCONCAVELEDBLUE
        Voltage:                3.0Vf-3.4Vf
        Current:                20ma
        Viewing Angle:      150-180*
        Color:                   460-465nm Blue
        Millicandela:          6,000-8,000mcd

    #5MMFLATTOPLEDBLUE
        Voltage:                3.0-3.4Vf
        Current:                20ma
        Viewing Angle:      105-115*
        Color:                   460-465nm Blue
        Millicandela:          10,000-12,000mcd

    #5MMROUNDTOPBLUE
        Voltage:                3.0-3.4Vf
        Current:                20ma
        Viewing Angle:      20-30*
        Color:                   460-465nm Blue
        Millicandela:          12,000-14,000mcd

    #5MMSTRAWHATLEDBLUE
        Voltage:                3.0-3.4Vf
        Current:                20ma
        Viewing Angle:      120-150*
        Color:                   460-465nm Blue
        Millicandela:          10,000-11,000mcd


I have them powered by a 4AA battery pack (6.0V) and each set of 10 LEDs (4 sets total) has a 150ohm 1W resistor to bring the power down to 3.2V.  Though that may be too many resistors or the wrong amount, me and Ohm's Law aren't best of friends yet.

I didn't have enough resistors to power the GREEN LEDs so I left them without power for this test. They are fairly bright and have a little "spark" of light at the tip of the dome lens when viewed from the side and a glaring light when viewed straight down through the lens at the diode.

So far the LEDs are just plugged into the breadboard (pointing mostly straight up in a sort of fan shape as they're smashed up against one another), and realizing they would be oriented differently inside a lightsaber blade, and have diffusion foam etc., this test will only give me a general idea as to how bright the different types of LEDs are and how they cast light.

I didn't want to start drilling the domes off of the domed LEDs without seeing how they functioned as intended first.  Down the road I may take two of each domed type LED and see how altering them changes the light output versus their unaltered counterparts.

One thing is for certain, I don't understand how everyone elses' LEDs look so bright in their test photos.  Either I'm underpowering my LEDs or the orientation is vitally important to how bright the LEDs appear, but mine sure don't strike me as being extraordinarily bright.  And I'm not 100% sure that the bottom row of LEDs are getting the same amount of energy as the top row LEDs are.  I'll have to pull the top sets off and see if that effects the output of the lower row of LEDs later tonight.  I still don't understand how if 40 leds powered by 6.0V don't light up very brightly, that you guys are getting 96+ LEDs to light up so wildly bright with 7.4V!?!?!?

I'll edit this later tonight with the photos I've taken so far (I didn't think this computer had a SD card reader so I left the camera at home, I'll know better for next time because it does!) I'm glad to have started this post though now while I have time to type, those "charts" are a booger to line up all the numbers!

Here's those pics!...

6V Way over resistored at 150ohm 1W per each 5 LED Strand...


6V Better resistored at 27ohm 1W per each 10 LED Strand (I don't have the proper 14ohm 1W resistors on hand at the moment)...








« Last Edit: February 06, 2017, 06:22:07 PM by Ridire Fíréan »

Offline Sincenatic

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Re: LEDS for String LED Blades - What's the difference?
« Reply #8 on: February 04, 2017, 03:14:53 PM »
This can be a very interesting experiment. It would, however, require a lot of work. What is interesting is to see how the LEDs work with diffusion and inside the tube. For example, solder five LEDs with the space in between that you plan to use, add diffusion and a tube, and evaluate the result. Repeat it for all kinds of LEDs that you have. Also, if the viewing angle is very narrow you would have to sand the LEDs. (I have never tried to drill down the top, but if you have the tools to do so, it is, of course, an option). Before doing this, be aware of that the camera is providing an important improvement, in particularly in darkness. 

When it comes to the resistor, I am not sure how you have wired the LEDs, but 150 Ohm must be way too much. For example, if you would like to light up one single LED with 20mA, your resistor would be (6V-3.2V)/0.02A=140 Ohm. If you would have five LEDs in parallel, you would like to provide 20mA*5=100mA=0.1A, and you would need a resistor of (6V-3.2V)/0.1A=28 Ohm. With 96 LEDs in parallel, you would like to provide 20mA*96=1920mA, but in this case it is possible that your battery cannot provide such current. If we change the example to a 3.7V li-ion battery, you would have; (4.2-3.2)/1.92 = 0.52 Ohm. I use 4.2 in the calculation because of the voltage when the battery is fully charged. Be aware of that when using a 7.4V battery pack, the idea is usually to wire the LEDs differently (to keep down the current).   

Offline Ridire Fíréan

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Re: LEDS for String LED Blades - What's the difference?
« Reply #9 on: February 04, 2017, 03:48:23 PM »
Thanks for the math Sincenatic!  Yes I had the #'s at 140 too, the local electronics shop had 150ohms in 1W resistors, so I used it to test the LEDs individually knowing they wouldn't explode in my lap as I was holding everything together with my fingers (the other day when the leds arrived and I didn't have the breadboard).  And I used them for the test, again, because I knew the LEDs would be safe, though probably underpowered.

And I'm kicking myself right now as I read through your post as I realize that I left without bringing home the equivilent of diffuser foam (albeit flat), I must have had 6-7 sheets of it in my hand throughout the day, I cannot believe that I forgot it.  I'll have to rummage through the basement and see if I have some hiding from past projects for this weekends tests, otherwise, there's always next week.

It's funny that you mention dark photography, looking at the LEDs last night as I was photographing them, I didn't think the LEDs looked all that spectacular.  I could see all of the clear plastic encasements save for the phosphur coated ones, and then just now as I was uploading them from the camera, the LEDs look more spectacular by far in the photos than they were in real life! (See pics above in a minute after I update my last post).

Offline Sincenatic

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Re: LEDS for String LED Blades - What's the difference?
« Reply #10 on: February 05, 2017, 10:26:02 AM »
In particular the 360 degree LEDs look promising, although I am sure that many of these will work fine in the end. Almost any foam will work to see the effect in the experiment. For the final blade I recommend the thinnest foam that you can find, unless you have closed cell foam (which I have never tried). The reason is that wrapping with too thick foam will leave a visible edge. I use 0.4mm thickness and I am very satisfied with the result.

Offline Ridire Fíréan

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Re: LEDS for String LED Blades - What's the difference?
« Reply #11 on: February 06, 2017, 06:17:36 PM »
Yeah, I've been thinking the same thing about the 360*'s myself.  That and the  #C503B-BAN-CY0C0461-ND CREE's are probably the brightest two sets.  I didn't have the foam I was looking for, but I did find some very dense white foam, a little too dense as I couldn't get a good gauge on which was brighter when covered by it.  I'll have to remember to bring some foam home tomorrow.

In the mean time, I've been busy!  Yesterday, Sunday, February 5, 2017, I reflowed my first ever Tri-CREE (White, Blue, Royal Blue) on a SinkPad-II 1938C that I modified myself with a little Ninja-nuity!  I guess that should be Jedi-nuity!!!  I may not be best of friends (yet) with Ohm's Law, but me and my Dremel tool go WWWWWWWWWAAAAAAAAAAAAYYYYYYYYYYYYY BACK!!!!!

And thankfully I'm becoming aquainted with my new Aven 200W Solder Pot (fancy reflow hot plate), and I used my Hakko FX-888D/FX-8801 for the first time today too after reflowing Tri-CREE's #2,3, and 4.  I got it last year for my birthday.  Guess it took a while to figure out if it worked or not, eh?!  I'm glad it does, and BOY DOES IT EVER.  It goes from Hoth-cold to Lightsaber-HOT in about 30 seconds!!!  I was giggling as I watched the little digital temperature screen go from naught to 750*F like it was in a race against Usain Bolt!  Man that thing is FAST~!

Anywho, here they are, my first four Tri-CREE LEDs...



I kinda over-cleaned #2, the Red, Green, Royal Blue, and the lenses on the Green especially, and the Royal Blue, became cloudy.  I guess they really don't like Isopropyl Alcohol after all!  Nor do they seem to like the paper towel I tried to dry them off with.  I took a wee dab of Meguiar's Deep Crystal Polish to them, and then some Meguiar's Ultimate Liquid Wax, but that didn't clear them up any.  Doesn't seem to have hurt them any further though, thankfully!

If anyone knows how to restore the surface of a CREE XP-E2 lens, PLEASE LET ME KNOW HOW!

 

retrousse