Amazing Cree CXA3070 LED

Wow, there is no comparison between Cree vs ebay cheap LEDs. Cree CXA3070 is one of the cutting-edge white LEDs at this moment. Compared to ebay COB LEDs, CXA3070 is putting out about 60% more light per watt!!! Most of us are happy with whatever we have been using until we see the difference since we don't know what's out there.

There are quite a lot of people who is using artificial light in this forum. So I thought this info may be useful. This is an update to my previous post in another forum.

OK, here is the punch line. CXA3070 is $40+$2.23 for holder, and 100W ebay LED is $8. So Cree is 5 times more expensive initially. But after running it 1.04 years, Cree becomes cheaper (I'm using $0.19497/kWh, which is probably higher than most of you). So it doesn't make sense to get the cheap LEDs. I started this thread with the cheap ebay LED. But now, I would recommend Cree CXA3070 over ebay LED. It's difficult to compare against florescent light (or red+blue type LED grow light). But I'm guessing that this CXA3070 is one of the most cost effective ways to grow with artificial lighting. The total costs is about $60 per 50W module of CXA3070 (pretty comparable initial cost to T5HO). You can drive it at a higher wattage (e.g. 100W), but I didn't want to push it to the maximum capacity.

Materials

1. LED:
   • Cree CXA3070-0000-000N-Z230F ($40 from digi-key) + LED Holder: TE Connectivity 2-2154857-2 ($2.23 from digi-key)
     vs
   • LED: ebay "100W" Warm White (similar to the one posted in the begining of this thread, but it has 100 diodes instead of 30 diodes for 30W). $8+free shipping from China
   
   CXA3070 (3000K) comes in 3 grades (bins) depending on the efficiency: Z4 (most efficient), Z2, Y4 (least efficient). Mine is the middle bin (Z2). The LED holder is a bit tedious to use (drill holes to the heatsink), but you don't have to solder/glue the LED.
   
   Here is the CXA3070 + holder:
   
   
   Comparison of the size:
   
   Clockwise from top left: Cree CXA-3070 (3000K, middle bin; Z2), ebay "100W" Warm White (around 3000K), ebay "100W" Cool White (around 6000K), ebay "30W" Warm White (around 3000K)
   
   
2. Drivers: I had 3 kinds of constant current drivers, all from ebay:
   
   From top to bottom: 50W (1.5A), 30W (1.05A), 20W (0.6A).
   
   
3. Heatsinks: whatever CPU heatsink with a fan.
   
   From Left to Right: Cree CXA3070, 3000K, ebay "100W" Warm White, ebay "100W" Daylight White, ebay "30W" Warm White.
   
4. Wire: Cerrowire 18-2 Thermostat Wire (18 gauge, 210-1002BR from HomeDepot).
5. Thermal paste: Arctic Silver Ceramique 2

Measurement:
Explanation of the data columns:

• "fc.1ft": I placed a light meter 12" away from the emitter, aligned to the center of the emitter. It was measured after running it for a minute or more (to stabilize the temperature).
• "input.W": watt used by LED + driver. This was measured by kill-a-watt meter.
• "Vf": forward voltage, the voltage across the + and - or the LED (unit: V)
• "current.A": current going through the LED (unit: A)
• "LED.W": watt used by LED (excluding driver). This is Vf * current.A
• Drvr.Effic: Driver efficiency. (=LED.W/input.W)
• fc.per.inW: footcandle at 12" per given input watt (=fc.1ft/input.W)
• fc.per.LEDW: footcandle at 12" per given input watt (exclude power loss due to driver) (=fc.1ft/LED.W)

Code:

LED        Driver     fc.1ft input.W    Vf current.A LED.W Drvr.Effic fc.per.inW fc.per.LEDW
CXA3070    20W(0.6A)     520    19.0 33.58     0.469 15.75      0.829       27.4        33.0
CXA3070    30W(1.05A)    970    33.8 35.04     0.864 30.27      0.896       28.7        32.0
CXA3070    50W(1.5A)    1500    59.0 37.03     1.427 52.84      0.896       25.4        28.4
ebay-100W  20W(0.6A)     320    18.8 27.51     0.552 15.19      0.808       17.0        21.1
ebay-100W  30W(1.05A)    480    27.2 28.06     0.866 24.30      0.893       17.6        19.8
ebay-100W  50W(1.5A)     730    46.0 28.81     1.425 41.05      0.892       15.9        17.8
ebay-30W   30W(1.05A)    520    30.1 31.01     0.866 26.85      0.892       17.3        19.4

LED on the left, and lightmeter on thr right:


Results (graphical representation):


Notes:

• With regard to the driver efficiency, those cheap ebay drivers (30W and 50W) are pretty good (89% efficiency). But the 20W driver is not great (around 82%).
• When you look at fc.perLEDW, you notice that efficiency of Cree and ebay LED increases with lower current. I think some other people calculated that radiant efficacy of this Cree can be >40% with 20W (0.6A) driver. In other words, 40% of electic enegy can be converted to light energy (the rest is wasted as heat).
• However, running Cree CXA3070 at lower current is a false economy. You can run 2x CXA3070 @50W, or 3x CXA3070 @30W to get the similar amount of light. But it takes 10.7 years to make the cost (initial + electricity) even (13h/day). So I'm going to run it with 50W driver
• As mentioned earlier, after 1.04 years (13h/day), Cree CXA3070 becomes cheaper than ebay LED.
• I was a bit surprised, that luminous efficiency of the 30W ebay LED isn't so different from 100W ebay LED.

These measurements are approximate. For example, the color spectra could be slightly different even though both Cree and ebay LEDs are warm white (around 3000K), and I used footcandle instead of PPF of PAR. Additionally, the light spread could be slightly different and 1-point measrement at the center may be misleading (I think the light spread looks similar).

 

xmpraedicta, you can kind of get the intensity-distance relationship by using inverse-square law. For example, at 24" (doubling the distance), you cab divide the data by 4 (=2^2).

I just put them together, so they are not used yet (except the ebay 30W LED), but I'll try to post a photo once I'm done with it. I still have to play with reflector like material (maybe pepsi plastic bottles + aluminum tape?) to adjust the beam spread. I'm going to use it on 3'(W)x2'(D)x2'(H) plexiglass enclosure. I'm planning to put it just on the enclosure, but I have to put some spacer for ventilation (create quite a bit of heat, and need about 4" of space), so it doesn't warp/melt the plexiglass. So the total distance between the LED and top of the leaves are about 2' (or a bit less) (but I'll probably need to adjust a bit).

I posted the light spread pattern in the previous post in orchid board (link in the 2nd para), but here is the photo (this is the 30W ebay COB on the right, and CFL on the left):


It has fairly wide spread, but your approach of using smaller LEDs has an advantage for the uniform illumination, though. If you want to make a focused pattern, reflctors with narrow angles are available.

So which color temp are you using for your XP-G rig? I personally think warmer white has a better spectrum for the photosynthesis, but cooler LEDs can put out more photons per watt.

 

Cool set-up, Calvin! So you are running around 31.5W per panel (1000mA * 12 * 3.15V). Mine (@50-60W) would be 6000fc around the 6" (with inverse square law), but CXA3070 is more concentrated, so I'm surprised that XP-G can give 5000fc. How narrow is the beam pattern of the lens (I think this is the cause you are getting such high reading?)? I can't quite keep track of different versions of Cree single LEDs, but I think XP-G is considered pretty efficient, isn't it?

I've also heard someone saying the combination of warm + neutral whites are good, but I didn't quite understand the logic. Most white diodes are blue emitter + yellow phosphor coating. Warm and Cool (daylight) whites use the same blue emitter, but different phosphor, and neutral whites uses different blue emitter. So you get wider spectra by combining NW+WW. I don't know if this is true or not, though.

Are you growing Dendrophylax (the top middle one in the 2nd photo in OB)?

 

Wow, congrats! I don't remember of seeing a post about it (nor I don't see it in your flickr), did I miss it? If you haven't posted about your Dendrophylax, I'd love to hear details about how you grow it (I killed mine...)!

I'll need to check if my light meter is functioning ok (compare it with the dslr). Mine is a bit old (even though it was the top-end model from Gossen).

 

This is a super easy version of DIY LED with high performance. Almost no tool required (wire insulation stripper does help). No need to solder nor drill, so much easier than the other DIY LED. Efficiency is pretty high (> 140 lumen/W).

Parts:

• LED: Philips Luxeon XF-3535L. ($19.37 from DigiKey)
• Driver: 900mA, 30W constant current driver from FastTech ($12.02)
• heatsink: Aluminum 3/4" C channel (about $13 from HomeDepot)
• 3-prong AC-plug
• 24-gauge wire
• Wire-Nut (something like this)
• Optional: Kapton tape (something like this, but you can get it cheaper via eBay)

Step-by-step assembly
The LEDs come as a flexible strip. Mine is 525mm long.



The backside of LED strip has adhesive already, so you peel the backing and attach it to the aluminum C channel (I cut the C channel to 22" length with a hacksaw) like a sticker.



This is the close-up of the diodes:



Each end of the LED strip has a connector. One is for + and the other is - (labeled). This connector (AVX 9176-400) is pretty simple to use. If you use 24 AWG (gauge) wires (either solid or stranded wire), all you have to do is push the wire in. You don't have to strip the insulation neither.



After I pushed in the wire, I used Kapton tape to cover it. It's unlikely to short it, but I happen to have Kapton tape.



You connect the + connector of LED to + (red) wire of the driver, and - connector to - (usually white or black) wire of the driver. I used this cheap driver (LEF-30W). Note that the sticker is reversed. So the DC output is actually on the left side with red and white wires (even though the label says that the DC out is right side). These are connected to the LED connectors. The wires of the driver are short, so you need to add a couple feet of 24-gauge wires (with wire-nut or solder).



Then the other side of the driver has brown, blue, and green/yellow (yellow with green stripe) wires, which is AC input. You need to connect an AC plug. The round stick is the Ground (refer to the next photo for the AC outlet). Then there are two flat blades; the bigger one is Neutral and the smaller one is Hot (Live). So you want to connect:
Green/Tellow = ground (round stick)
Brown = Live/Hot (smaller flat blade)
Blue = Neutral (bigger flat blade)



That's all you have to do. Here is the assembled and finished LED. I use soldering, but you can use wire-nuts to connect wires.



A test run. It doesn't look bright in the photo, but it is pretty bright, so you might want to wear sunglasses.




The next photo is showing the beam angle. From 1' distance, it provides about 2' wide homogeneous light. The C-channel looks like a decent reflector. The Cheerio box is not an ordinary Cheerio box. It is modified, and it is actually a DIY spectrophotometer.



The aluminum C-channel, which is acting as a heatsink, does become quite warm, but it is not hot. A better heatsink would improve the efficiency, but the cost will go up quite a bit (LED is more efficient, when it is kept cooler).

Measurement
Driver:
AC input: 22.7W
Vf: 21.38V
DC current: 906mA
Driver efficiency: 85.3% (a bit low-end)

Light measurement at 1' away from the LED in the middle:
PPFD: 110 micromoles/m^2/s
footcandles with LX1330B: 655fc
footcandles with Gossen Ultra Pro: 420fc (the response curve of this meter is quite different, but I'm including it for the comparison with the measurements of my older posts).

The LED is about 2' long. Here is the values of 1x 24W 2' T5HO (actually consumes about 18.15W per bulb in 4 bulb fixture).

AgroBrite 6400K 24W (brand new)
PPFD: 58 micromoles/m^2/s

AgroBrite 6400K 24W (2 years of use)
PPFD: 33 micromoles/m^2/s

Odyssea Plant 24W (new, purplish "plant" light)
PPFD: 81 micromoles/m^2/s

Odyssea Plant 24W (after 3-5 months)
PPFD: 63 micromoles/m^2/s

With 4x bulb fixture with 4 bulbs in it (bulbs are not brand-new), you get
PPFD: 160 micromoles/m^2/s

So 2x XF-3535L (45W) can outperforms (about >30% more light than) 4x 24W T5HO (consumes 72.6W). The cost of this DIY LED is similar or cheaper than 4x 2' T5HO.

Comments:
There are several versions of XF-3535L. I chose 4000K version. This can do 147 lumen/W if you are driving it at 800mA. I couldn't find a cheap 800mA driver, so I'm slightly driving it harder (900mA). This means the efficiency (i.e. the amount of energy converted to light instead of heat) is a bit lower than 147lumen/W. With any LEDs, if you drive harder, the efficiency goes down. Warmer ones like 3000K may have slightly better light suitable for plants because it has more red light. The lumen/W goes down if you use warmer light, but lumen isn't a good measure for plants. From several measurements I have done with LED (with PPFD of PAR, not irrelevant fc or lux), the output relevant for plants (PAR) doesn't go down with warmer light. So I think using 4000K or something lower than that is optimum. Also XF-3535L comes in several CRI. Stick with the lowest CRI for the given corrected color temp (80 CRI instead of 85 in case of 4000K). Higher CRI ones have lower output for plants. There is also 4' version (and 900mA driver works well), so this would be a good candidate to replace 54W T5HO.

Note that the performance of this LED is impressively high. But the price is relatively high compared to COB LEDs like Cree CXA3070 or Bridgelux Vero series (I recently assembled Vero 29, and I'm very impressed by it, I'll try to post more about it when I get some time). It is difficult to compare the performance between COB and the linear XF-3535L, but I'm guessing that they are pretty similar to each other. So if you are for ultimate cost-performance ratio, go with COB. DIY COB-LED is pretty easy, but it is slightly more time-consuming than this strip light (e.g. drilling holes and tapping). There are also other high performing COBs from Citizen and Samsung, but I haven't found a good source to get a few samples. I also heard that improved LEDs are coming out pretty soon. So year of 2015 will be exciting for us artificial light growers!

Note that there are lots of other "strip-light"-style LEDs. Most others are not worth using for plants. The efficiency is really low (for most of them).

 

Daniel, at this moment, there is a huge difference in performance of LEDs (you can easily get 2-3 times more light per energy consumption if you compare the high end vs low end products). By looking at the specs, XF-3535L seems to be close to the top-end of current white LEDs. I have tried a few cheap LEDs, too, and did some calculation about the long-term cost. My conclusion is that you save money by going with the higher performance LEDs; e.g., you can get Chinese Epistar/Generic LEDs for 1/10 of Cree, but it is not worth buying them since you'll be paying a lot more money for electricity. I don't want to sound like an elitist, but my point is that with light, the initial cost is a relatively small portion of what you'll be paying for. So for us artificial light growers who has to use it for 13 hours a day, it makes sense to pay extra initial cost for the highest efficiency. Then you can use the saving to buy more orchids! I personally think that people who can do a bit of DIY can save quite a bit of money (and environment) by migrating to DIY LED from florescent light.

This XF-3535L is pretty new to me (I didn't know about it until a couple weeks ago), but it seems to be a pretty good option (with availability). XF-3535L seems to have high performance, but it is not the cheapest. So if you have a drill press, I think Cree CXA3070 or Bridgelux Vero 18 or 29 gives cheaper initial cost with similar (and proven) performance. It costs around $35-40 to get 20W for XF3535L vs $50-60 to get 50-60W with CXA3070 or Vero. But you can't beat the easy assembly of XF-3535L. It is a bit too new to say how well it will perform in a long term (i.e. decay in output etc, CXA3070 and Vero has been used by many growers by now). If I need lots of light, I would definitely go with COB, though (because of the cheaper initial cost).

The choice also depends on the target area (how much light you need, and what kind of shape the growing area is). CXA3070 or Vero will provide a circular growing area. But when it is running around 50W, each can cover slightly less than 2'x2' area easily. So for my 4'x4' grow tent, I use 4 of them to cover a single level. So if you know the size shape of grow area you want to cover, and what kinds of orchids, I might be able to see possible alternatives (if slightly more complicated assembly is ok with you). If you were thinking 1-2 Ray's, then the XF-3535L similar to mine might be a good choice.

There are several form factors of XF3535L, but the coverage is more linear than COB like CXA3070 or Vero.

A. 300 x 10mm
B. 600 x 10mm
C. 525 x 5.25mm
D. 1150 x 5.25mm

A & B have the same number of diodes per strip (diodes are more spaced out for B). D is basically twice the 525mm (C) version. So these are pretty good to replace 2' or 4' florescent light. And here are some specs:

A&B: 10.8W (600mA, 18V) $13-14.5
C: 16.8W (800mA, 21V) $19.37
D: 32.4W (900mA, 36V) Not available yet, but I'm guessing around $43.

Sorry that it became a long reply. But the point is, I think XF-3535L is pretty good. So I think you should give it a try (let me know if you need any help assembling it).

I do have Ray's LED, and I like it. It is very convenient, and it seems to have good performance for the price. But I'm pretty sure XF-3535L is quite a bit more efficient. It is not easy to compare the total output because they have different beam shapes (I think 2x Ray's have a similar coverage area as 1x 535mm XF-3535L). Lumen comparison is a bit misleading since Ray's have some Red LEDs (meaning it will give more useful light than what lumen says). From the spec, 4000K 525mm XF-2525L puts out 2464 lumen at 16.8W with 147 lumen/W (mine is driven harder, so putting out more total lumen but less lumen/W), and Ray's is 1200 lumens with 13W with 92.3 lumen/W (which is better than Cree 9.5W household LED bulb). At 1' from the light source, I got 110 micro moles/m^2/s with 23W. Ray's is 55 micro moles/m^2/s with 13W (from Ray's web page).

 

Cool! I've been using it inside of my orchid case, and it is working great. The aluminum C-channel doesn't seem to be too warm, maybe due to air movement by circulating fans. When I put cheap eBay 30W COB inside of the case (3x2x2'), the inside temperature became too warm. But with 20W XF-3535L, the inside temp goes up only a little bit.

C-channel seems to be sufficient for me (fairly cold), but Scaramento is quite a bit warmer than here. I was originally looking for H-channel, but I couldn't find it locally. I considered making H shape by putting 2x C-channel back-to-back (after sanding the surface well, and putting thermal paste, something like this, between the two aluminum channels), but I decided that it was too much work.

If you want a better heatsink, I've heard good things about heatsinkUSA: 2.079" x 24" is about $7.68. Also, there are some heatsinks for strip LEDs, but I don't have experiences with them.

 

I think you are right. My P. gigantea (and other warm Phals) are slower due to luck of heat in Alaska. But I mentioned my impression of heat inside of the case to imply higher efficiency of XF-3535L. Efficient LED should convert more electricity to light than to heat, so in theory, it should release less heat to the case. But I didn't make any measurement, so I can't quite say it.

Better cooling of LED with better heat sink is generally a good thing; lower operating temp contributes to higher efficiency and possibly longevity.

Are you thinking of polishing aluminum to increase the reflection? If you do, please let us know how it goes!

I just received 100W eBay driver from China a couple days ago. I'll test this with Bridgelux COB Vero-29, and report it back here. But it won't happen for a while (a bit too busy now).

 

I made a blog post about how to make Chip-on-board (COB) based LED fixtures (here is the link). The basic contents are similar to what I posted earlier in this thread. I included a little bit more assembly details (maybe too much for most people), information about driver selection, and new measurement data using PPFD. Also I came across a couple of useful youtube videos, so the links are provided at the very end of the post. I started this thread with cheap eBay COB, but the video provides the reason why these are not worth getting.

There are newer generations of COB LEDs (Bridgelux Vero Version 2.0 and Cree CXB series) after I posted the messages in this thread. Some people are achieving close to 70% radiant efficiency with Cree CXB3590 (only 30% of electricity is wasted as heat, and 70% is converted to light energy). Don't be left out from the advance in a "cheaper" way to grow orchids under artificial light!

 

T8-LED has been improved, and the efficiency is getting improved. 100lumen/watt is reasonable, and better than any fluorescent light! You might want to check HomeDepot. They have Philips, which has slightly better efficacy than Feit.