DIY LEDs - The write-up

[Quartapound]

I don't have enough experience (or a par meter) to know if I have enough, not enough, or too much light.

I'm starting things off low and will make gradual adjustments, as I do have some livestock in the tank.

I'll stick with 710mA until I've reached 100% power on my dimmer, then maybe play with higher current

 

[TheFishMan65]

Thanks - I found it. Somehow I have never gotten quite that far

 

[Jay03GT]

This has probably been covered, but I can't find the answer after looking for a few hours now. What is the max spread desireable for 2 parallel strings? I have 2 strings of XP-E RB and Bl, 11 in each string running off a Meanwell 60-48D driver. When I first fired them up I had about a 30mA seperation, not bad. After running them for almost a week now I have 736mA on one string and 795mA on the other. I know you want them fairly close, but how close is preferred? What are the consequences of having unbalanced strings? Thanks in advance.

 

[tony.hebert]

Curious why there is so much interest in Cree and Meanwell? I have no experience with these products and can appreciate that they may be well made. But it seems to me at 3 to 4 times the price of equivalent products from China it will quickly turn a 300 dollar project into something around a thousand dollars. They can't be that much brighter, last that much longer. What am I missing?

 

[firechild]

Curious why there is so much interest in Cree and Meanwell? I have no experience with these products and can appreciate that they may be well made. But it seems to me at 3 to 4 times the price of equivalent products from China it will quickly turn a 300 dollar project into something around a thousand dollars. They can't be that much brighter, last that much longer. What am I missing?

With regard to Meanwell, you're probably right. They just became the standard for aquarium DIY projects by default because the ELN series fit our needs perfectly and are readily available. At $30 there probably isn't a huge saving by going with cheaper products.

With respect to Cree, it depends what your goals are. If you want low setup costs and aren't worried about long-term costs then go with the Chinese emitters. If you want overall savings, Cree emitters are probably going to be ideal. They are much more efficient and could save you running costs of 30-40%.

 

[cediss]

Cree also is known to work well for SPS. The results with other emitters not as standard or consistent results. Cree has greater output and efficiency. Better to buy USA especially when proven better results. If going LPS, save money and buy cheap emitters

 

[tony.hebert]

Cree

Cree

With regard to Meanwell, you're probably right. They just became the standard for aquarium DIY projects by default because the ELN series fit our needs perfectly and are readily available. At $30 there probably isn't a huge saving by going with cheaper products.

With respect to Cree, it depends what your goals are. If you want low setup costs and aren't worried about long-term costs then go with the Chinese emitters. If you want overall savings, Cree emitters are probably going to be ideal. They are much more efficient and could save you running costs of 30-40%.

I can appreciate this argument. I want lower running costs. So I wanted to verify the assertion. But I have run into two problems.

FIRST PROBLEM: I can't verify what the Cree lumens per watt are. According to their site they rate 122 lumens at 350 mA for their high efficiency white. Why not say what they rate at full power? I think because they are more efficient at this power level (about one watt), the efficiency drops past this power level. I did find one full power claim of 300 lumens for a 5 watt chip which is 60 lumens per watt. Which is equivalent to the chinese chips I purchased on EBAY for a third the cost. The specs for the chinese chip are below:
Wavelength: 470nm
DC Forward Voltage (VF): 3.2-3.8V DC
DC Forward Current (IF): 700mA MAX
Viewing Angle: 120 Degree
Intensity Luminous (Iv): 180LM

SECOND PROBLEM: Assuming that you are correct and CREE are more efficient well then how long would it take me to break even and start saving some money?
I am going to use 35% more efficient which is right in between your estimate.
So lets use one 3 watt LED for the math cause it's more simple and I am not
that good at math. (please verify) using 70000 hours of lifespan as average

3 Watts x 70000 hours (rated lifespan) = 210 KW hours
210 KWh x 7 cents per Kwh (my rate use your rate) = $14.70 lifetime power cost
If CREE saves me 35% of that I get a $5.15 cent savings lifetime on my 3 watt LED
But 5 bucks in savings takes 16 years if you burn it 12 hours a day.

So if my math is right (and it probably isn't) I should be able to buy cheap
Chinese LEDs and replace them in 8 years for the newest coolest more efficient LEDs for less than or equal the cost that someone paid for their CREEs even IF they are 35% more efficient.

Regards,

Tony

 

[tony.hebert]

Cree

Cree

Cree also is known to work well for SPS. The results with other emitters not as standard or consistent results. Cree has greater output and efficiency. Better to buy USA especially when proven better results. If going LPS, save money and buy cheap emitters

I am a skeptic and don't mean disrespect. My guess is that my SPS will thrive within certain wavelengths and intensities and don't care at all where the LEDs where made. I would be interested to look at the data that proved this.

Regards

Tony

 

[tony.hebert]

parallel strings

parallel strings

This has probably been covered, but I can't find the answer after looking for a few hours now. What is the max spread desireable for 2 parallel strings? I have 2 strings of XP-E RB and Bl, 11 in each string running off a Meanwell 60-48D driver. When I first fired them up I had about a 30mA seperation, not bad. After running them for almost a week now I have 736mA on one string and 795mA on the other. I know you want them fairly close, but how close is preferred? What are the consequences of having unbalanced strings? Thanks in advance.

Hi Jay,

I don't feel qualified to answer your question but I do feel I veered the thread after your question with my CREE rant and now feel responsible that you don't have an answer yet. This is my two cents: They wont be the same and I don't think it matters much. Assuming that you are using a limiting resistor of adequate power rating that you calculated with the online tools that are available I wouldn't worry. From the LED center:

The long answer: LEDs are semiconductors, diodes in particular. The current flowing in an LED is an exponential function of voltage across the LED. The important part about that for you is that a small change in voltage can produce a huge change in current. That is the most important concept of this article. Resistors aren't like that. The current and voltage in a resistor are linearly related. That means that a change in voltage will produce a proportional change in current. Current versus voltage is a straight line for a resistor, but not at all for an LED.

Because of this, you can't say that LEDs have "œresistance." Resistance is defined as the constant ratio of voltage to current in a resistive circuit element. Even worse, there's no real way to know exactly the relationship between current and voltage for any given LED across all possible voltages other than direct measurement. The exact relationship varies among different colors, different sizes, and even different batches from the same manufacturer.

 

[Garage1217]

Some led products / drivers from china are great. Some are total crap. Very hit and miss. Sort of like shopping at harbor freight. If you weed through the crap, they actually have some really good, affordable stuff. I have tried several overseas / more affordable high power leds and drivers and have gotten a mix of good and bad. Everything from drivers that had the wrong cap values which caused them to blow up (literally) in short order to leds that ended up having bubbles in the lenses and that smoked rather quick when run under their rated specs. Also many of the led specs and wavelengths are total bogus, just made up numbers to sell a product so you never know exactly what you are going to get.

I do not think anyone here is obsessed with cree or meanwell, but many use these brands specifically because they are both rock solid products and actually very affordable IMO as you know what you are getting color and quality wise if purchased from a reputable vendor. If wired and setup / cooled properly they are near setup and forget.

 

[wfournier]

I can appreciate this argument. I want lower running costs. So I wanted to verify the assertion. But I have run into two problems.

FIRST PROBLEM: I can't verify what the Cree lumens per watt are. According to their site they rate 122 lumens at 350 mA for their high efficiency white. Why not say what they rate at full power? I think because they are more efficient at this power level (about one watt), the efficiency drops past this power level. I did find one full power claim of 300 lumens for a 5 watt chip which is 60 lumens per watt. Which is equivalent to the chinese chips I purchased on EBAY for a third the cost. The specs for the chinese chip are below:
Wavelength: 470nm
DC Forward Voltage (VF): 3.2-3.8V DC
DC Forward Current (IF): 700mA MAX
Viewing Angle: 120 Degree
Intensity Luminous (Iv): 180LM

SECOND PROBLEM: Assuming that you are correct and CREE are more efficient well then how long would it take me to break even and start saving some money?
I am going to use 35% more efficient which is right in between your estimate.
So lets use one 3 watt LED for the math cause it's more simple and I am not
that good at math. (please verify) using 70000 hours of lifespan as average

3 Watts x 70000 hours (rated lifespan) = 210 KW hours
210 KWh x 7 cents per Kwh (my rate use your rate) = $14.70 lifetime power cost
If CREE saves me 35% of that I get a $5.15 cent savings lifetime on my 3 watt LED
But 5 bucks in savings takes 16 years if you burn it 12 hours a day.

So if my math is right (and it probably isn't) I should be able to buy cheap
Chinese LEDs and replace them in 8 years for the newest coolest more efficient LEDs for less than or equal the cost that someone paid for their CREEs even IF they are 35% more efficient.

Regards,

Tony

Cree actually does post the lumens at full power, they just do it a little differently (as does Bridgelux so I imagine this is how it is generally expressed in the industry). I actually pulled up the current data sheet for the XP-G LEDs and they list the output at 350 ma, 700 ma, 1.0A and 1.5A. However the way I always figured it out was to look at the "Relative Luminous Flux" chart. This plots intensity as a percentage against various currents. You'll notice that 100% lines up with 350ma as this is the standard "benchmark" current used. You can see that at 1.0A the output is 250% of what it is at 350ma so simply multiply the lumens at 350ma times 2.5.

As for the cost aspect and if spending the additional money is worth it only time will tell. They very well may be the better deal (I actually have some waiting to be used).

However I would suggest that any data sheets you see on the chinese LEDs be taken with a grain of salt. They are notorious for being a little liberal with their output numbers.

 

[reefermad619]

If my electricity cost .07/Kwh I would totally stick with MH/T5 combo. But it's not, so here I come LEDs.

 

[BlueCorn]

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