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Comparison of two kinds of COB for LED Grow Light

Currently there are two types of integrated chip set, simply called ”COB” in grow light industry, one is made by particular LED lamp for precise color ratio ( called “precise model”), so that plant will have adequate adsorption of particular light for their different growing period(vegetative stage and blooming stage); the other is by applying a layer of refined fluorescent powder above a certain group LED lamps in different wavelength (called ”full spectrum model”).

The two types of COB are just like below image, the left one is “precise model”, and the right one “full spectrum model”, and they are from different making with different advantage of plant growing.  

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However, which one is better for plant growing?

Firstly let us analyze the actual spectrum diagram from the two models:

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We can see clearly that there are 6 peak value of wavelength, they are respectively generated by 400nm, 430nm, 460nm, 630nm, 660nm and 740nm, as is known to all that these wavelength are the main absorption during photosynthesis of plant in different stage of growing, it shows that plant is able to get best photosynthesis activities both in vegetative stage and blooming stage, these precise color ratio ensures the plant get good absorption no matter in any stage of growing.

Due to encapsulation of LED lamp of different colors are singly encapsulated on the COB, plus with proper electric current and good heat-dissipation solution, the precise COB model is able to enjoy a long lifetime.

Now let us look at the so-called full spectrum version, we can see from the below spectrum diagram, there is a obvious two wavelength cluster, one is blue, the other is a combination of green, yellow, red.

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We knew that good photosynthesis comes only when the plant receives the adequate but peak value of light, then the photosynthesis will be considerably effected, but we can only see there are only two peak value, one is 450 (or 460nm), the other is 600nm from the above, but we knew that just these two peak wavelength is not enough for the plant growth both in vegetative stage and blooming stage, so the promotion of growth of plant cannot be highly expected;

In addition, there are below points we need to consider on this COB making:

1-   As there is a florescent powder above a group of LEDs of different colors, when much heat created on COB during the working of grow light, there is a liquidity of florescent powder on the COB, so the color will be even slightly altered due to the liquidity florescent, such making of full spectrum version is also much cheaper than precise model, but as time goes on, the wavelength will be changeable, the plant will have no good color ratio for the vegetative stage and blooming stage, although such model always produce good data of luminance, as we knew that the Par value of light is not only decided by luminance of light, but most importantly the color ratio.

2-   The another important fact is that the refined florescent powder of full spectrum COB is mixed with a certain of different color florescent powder, the workmanship is hard to control during the mixing of different powders, so it is usually hard to guarantee the same and precise wavelength when it is from different batch production, it means that there will be different color ratios and spectrums of grow light from different color ratio, there is also big difference in color ratio and spectrum once there is a very small difference in mixing of powders;

3-   Such COB are just by fixing all blue LEDs in COB, as we knew that blue color LED always creates so much higher heat than red color LED, so unless there is a perfect heat-sinking moule, otherwise, lifetime of COB cannot be safely ensured;

4-   Due to red color is excitation light by red floresent which is very easy to get light attenuation quickly after a certain time of using, it is more than 30% light attenuation after 1000hrs, which also reduce the lifetime of light sources.

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