Epistar 3W LEDs are that bad?

[danbwc]

Hey guys,

I've seen some complaints about these Epistar 3W LEDs:

But I thought these were similar or the same from ViparSpectra LED panels and they received a lot of good reviews.

Do you guys know if they ain't a good idea for a DIY LED grow light?

Also, how better are LED grow lights with a lot of small sources compared to ones with less sources with a higher wattage?


Thanks!

[Tazard]

I don't know man I thought epistar 3w was what you wanted. My LED's use them.

[danbwc]

Any burnt already? How long have you been with these? Thanks for the reply dude!

[Tazard]

Only had them since July 6. No issues.

[Zativa]

A few bits of reality from someone who spent 45 years in the engineering biz and designed MANY circuit boards: You are choosing to fight an uphill battle. Buying an assembled and working light fixture is cheaper in the long run and produces better results. The circuit board itself is an active part of the design since it absorbs a LOT of heat from the LEDs. You also need a pulse-mode power supply to get the most out of high-power LEDS without frying them. And prices for LEDs are so much lower in high quantities that you can't hope to compete. I threw $70 each at Amazon for a couple 'Roleadro' 300 W panels ($70 each, made by GalaxyHydro) and have seen excellent results with them.

[danbwc]

Thanks for this guys!

So, you say more current is less efficiency. But if I keep the current constant in 680mA, the blue LEDs with a forward voltage of 3.4V will produce around 2.3W and since they are not a great brand I can say much less than it will be turned into light. But if I go for 600mA it will produce around 2W, but the same relative share (%) will be turned into light (efficiency keeps the same), no?

[DrPhoton]

Its about the ratio of what you put in and what you get out, the lower the current, the less energy is wasted as heat.

[danbwc]

I see it now, thanks man! I will try to run the LEDs with less than the maximum current. But they will be dimmable also..

[DrPhoton]

Zativa is right, cost wise i dont think you would find a cheaper direction unless you build a more efficient system than todays standards. Which are actually quite poor.

The problem with LED chips is that they are designed with photometry in mind, not radiometry. This makes it difficult to design for grow lights as LED manufacturers do not provide all the information to make the best design choices.

LED grow lights today, are poorly made, because they fail to incorporate electronic engineering with 'correct' plant biology and provide poor and misleading advertisement. A pure example is from company's like kind LED and many others, that try to state that photosynthesis only happens in a very narrow portion of the light spectrum.



However its well known by people who have studied botany or plant biology that plants use light across a wide spectrum. This is well known as the mccree curve.



This curve is a plants photosynthetic response sensitivity, which can become more linear across its spectrum with increased light intensity. So much infact that green can have a higher quantum yield than blue.

To really get the best out of LED technology, you really need to have a grasp on electronics, light physics and plant biology.

[growmore]

You will also need to include voltage regulation circuits if you intend using different colour spectrum chips, as different colours have different working voltages.

[Tazard]

Just for my purposes was I applying a zener properly? 😂

[DrPhoton]

Yes tazard, thats correct. Implementing zener diodes or switching circuits is used in small applications to prevent a complete open circuit. However doing so can get complicated and costly when you are dealing with larger arrays. It really depends i think. However i think with large array light solutions such as we are talking about, we are looking at a parallel series configuration that arranges segments into clusters. Allowing more robust failure prevention and diagnostics. I am looking further into these topology's, there are many ways to go about configuring it.

[Tazard]

Thanks

[DrPhoton]

This is going slightly beyond my scope, i understand the technology around solid state devices but do not go too far into wiring topology.

First lets look at the technology, the drivers and then the topology last, which i may need help with.

Solid State Lighting:

Ultimately for the most efficient system, you want as much energy as possible, going into light, rather than heat. When looking at solid state lighting and color, blue is the most electrically efficient, this is why blue typically has the highest rated forward voltage, because less energy is being wasted through heat and its max junction temperature is reached at a higher forward voltage.
The efficiency of solid state lighting devices depends heavily on the junction temperature, which in turn, primarily depends upon three factors. The applied power, the thermal resistances between the junction and the ambient temperature. This is why when applied power is lowered, efficiency increases as thermal resistance across the junction decreases.
When looking at the efficacy (very important difference between efficiency and efficacy) of solid state lighting, this is referring to photometry and the perception of light by the human eye. For example, white has about the highest efficacy compared to other colors and so it is used primarily for environment lighting solutions for our visual needs.
Electrically speaking however, white is much less efficient than other colors such as blue or red because more energy is wasted as heat. Also because all colors are usually derived from blue, any result will always end up being less efficient from the color from which it is being made from.
For growing, you do not! want to use photometry to dictate your design. You want to use radiometry as plants have their own response curve that more closely match a linear sensitivity. For more information between photometry and radiometry read my article on light metric systems.

Constant Current, Constant Voltage And Wiring Topology

This is really going out of my depth and you will know better than me on this.
The different wiring configurations all have different applications and strengths. From what i know, the most efficient from a wiring configuration, would be a constant current with a series array. But would only be really good for few numbers of diodes. For larger arrays i would think something similar to what you suggested, series parallel ?.
That way you can have clusters of series which will allow the rest of the circuits to operate when certain clusters fail. But would you still use a CC or CV driver ?.

[DrPhoton]

Yup yup yup

[Paracelsus]

You can find independent lab test results on various top selling LED manufactures on the ChilLED web page , Growmau5 works with them now and is the COO his real name is Brian. The Grow Mau5 went into a retreat

Here are the reports https://chilledgrowlights.com/independent-lab-reports

[DrPhoton]

Its good to see manufacturers start supplying this type of data, very interesting paracelsus.

[danbwc]

Basically,this is the circuit. I've drawn the cc driver only once,but it repeats 5 times for each power source (1 for each array of LEDs). At the bottom on the right side is written the disposition of the LEDs for the second power source. The PWM which dims the LEDs will be the same for equal wavelenghts, thus I can dim different colours through the stages of the plants. I'll wait for some opinios in here before working out the disposition of the LEDs on the large heatsink.

I decide for 600mA so I can have a better efficiency (thanks for this info Dan) than 700mA. I was thinking about adding a couple IR (850nm) LEDs and UV (390 nm), would be a good idea? How many?

Any suggestion about the spectrum? I'm thinking about changing some 620nm and 660nm for 595nm to get a better spectrum.

I'll include separated heatskins for Q1 and Q2 also.

Sorry about my handwriting haha!

[DrPhoton]

Yeah I actually said that wrong should have been density of ppf not par as par is constant irrelevant of location.

Well actually PPF is a measurement technique of total light output, measured with such devices as an integrating sphere. When you take PAR readings from a unit of area, thats PPFD.
Thing is, a single PPFD measurement with artificial light, does not show you your lights output capacity. In actuallity, it only shows a PPFD reading over the diameter of the sensor only, not per square metre. Unless you are measuring a light source such as the sun where light is uniform in any direction.
Thats why measurement systems without integrating spheres will take readings from multiple locations accross the entire canopy and calculate a figure called the canopy average. Although no where near as accurate as a true PPF reading, its the best we have without having to fork out a lot of money.

To answer your question. Although if you take the same measurement say from the center would be lower after you raised the light. You would find that other readings outside the center would actually increase. Due to the spread of photons. So as i have said previously, its just the spread and uniformity that changes but the overall capacity doesnt change unless it losses its energy through conversion to heat (hitting at object).

-------------------------------------------------------------------

My apologies tazzard i believe i misinterpreted your question. You were asking if PPF changes due to the lower PPFD meadurement when raising a light.

As previously said above, the uniformity increases but the PPF stays the same.

[Tazard]

Entropy?

[DrPhoton]

Thermodynamics is beyond my scope, but yes perhaps entropy ? Is that when energy moves from one form to another ?

[DrPhoton]

This is not entirely related but i wanted to put this conversation here as it was good information that i would like to use to refer people to in the future.

Hello,

I've read several of your posts and you seem to have a passion for light technology. Do you have a COB LED unit that you would recommend?

I don't have the skill to build a DIY unit, so I'm looking for a commercial unit.

Thanks.

Hey there dragon, i have a passion for many areas of science. Personally i have not decided to choose LED over HPS because as far as looking at it from an electrical engineering point of view, they are not quite better...yet. But they are not far off. Really its not the technology that prevents LED from being better than HPS, but the manufacturers and cost factor preventing it from being a ideal.

Electrically, LED is more efficient watt for watt. But not by much, they are between 10-20% Max. But grow light manufacturers dont utilize this potential because of the cost limitation. It costs a lot to get that efficiency level.

Saying that, it wont be long when it will be indefinetly better. Semiconductors follow a law called haitz law and eventually it will completely replace all other light technology. As an electrician, LED'S have been a residential and commercial product for nearly 20 years. However its only of the last decade that they have been a more efficient and superior technology compared to other light technologies such as fluorescence, incandescence, compact fluorescence.

For grow light products available today, the only light i have seen that shows a real benefit over HPS is the products by spectrum king. Many like the kind LED but from memory i felt they were not very efficient.

I tell you what, i will have a good look at popular LED products and see if there are any that are decent.

Talk soon.

Thank you for your reply, I would appreciate your opinion.

I had a look around and could not see any other definitive brands with comparable products compared to kind LED and spectrum king. Although virpaspectra has some nice products with some seemingly more reliable marketing. They appear to be a good bang for buck brand and i am sure i have seen a couple of threads about them over the last few months. One particular model is the vipraspectra 700 with individual dimming controls for three color bands. This gives great flexibility and control for the user to define the lights color balance. Specially for me because i would use them quite a lot during germination and early vegging so i can ease them into full power. Giving them more blue than red in veg and then full power red in flower with a slight rollback of the blue.

But manufacturers dont provide any specs that you can use to 'actually' know what its power output actually is. Whats really needed is radiometry data. The typical PPFD at specific heights is completely crap on its own and says practically nothing about the lights capacity.
So look at vipraspectra, kind LED and spectrum king. See if you can find any youtube videos with people testing the lights, like how monster garden does with their famous light bult tests. Multiple PPFD readings over the entire canopy and then averaged out. This is the only way outside the manufacturers standard provision to know what a light actually puts out.
For comparison, 600W HPS has around 400umols canopy average, 1000w just over 520umols. With the best reflectors out there, this can be pushed to 800umols. A lot of energy is wasted from most mid range reflectors.

Compare those to other LED test results (if any) and compare the input power to output energy ratio to work out the efficiency difference.

Danny.

Thank you very much for looking into this. I had a look at Spectrum King and their SK600 looks awesome but more than I am willing to spend on my hobby. I was told I could write off costs as a medical expense since I have a recommendation.

I will have a look at Viparspectra, they seem to be an affordable choice. Any thoughts on CMH?

CMH has been tested quite a bit and unbeknown to most growers, there are heavy studys comparing light technologies. The most popular one is the economic analysis of greenhouse lighting.

They used an integrating sphere which is highly accurate and shows the entire radiant flux (total light output), so not a half assed or a cheap study. It shows that CMH is barely better than 1000w HPS. However not better than double ended HPS. DE is better by a significant margin. I would even argue that 600w HPS is probably as good or even better than CMH as the 600w bulbs are known to be more efficient than their 1000w counterparts due to chemistry. Which the study had not applied to their study.

Really, comparing CMH to HPS to LED right now, is really not about, which is more efficient. Because at this time, they are all very close. The question is, which has the best fixture cost per umol. Which HPS is far better by a large margin. Pay close attention to 'photon efficeincy' and 'fixture cost per umol' in the provided study. This will show you the important details between the technologies.

Danny.

[Tazard]

Here is a circuit very close to the one you are showing me. There is current limiting resistor to protect the leds. I think if you forward this to him that it'll get him on track

http://www.reuk.co.uk/wordpress/lighting/led-dimmer-circuit/

from my dad

[Tazard]

No problem. He asked what the LED's were supposed to do. 😂 I told him "make light" but I see the reference is from a mj based source. He isn't dumb, he gave me my first HPS lol.

[danbwc]

Lol hahah good luck with your plants man, thanks for the support

[Tazard]

Anything anytime

[DrPhoton]

One thing to also think about that we have not covered yet but will likely not be importent until the final build is the optics. Optics play a big role in the control and dispersion of light. Its analogous to regular lights with reflector hoods. The great thing about LED lights is the ability through optics to focus the light more. Light hoods loose energy through reflection loss and their often poor design in small grow areas adds to that when they are often reflecting off walls or directing light beyond the canopy and completely missing the plants. With optics, light is made to collimate more and shows more control with light, with very little energy loss (the energy lossed through optics is far less compared to reflection).

So the decision on the chips and their optics is important so that you can control light to be used as efficiently as possible. This comes down mostly to the optics beam angle but also how you arrange the LED's, spacing and placement all have an effect. The goal is to create a well focussed light that does not leak outside the intended canopy area but also have great uniformity. Uniformity both horizontally and vertically is the key.

However this is likely going to be an even bigger struggle compared to just building the light itself. It really shows the complexity involved in building a light.

[danbwc]

Yes man, I've been thinking about the lens. But how can I know how far the light is reaching? I need to find some data about these LEDs and work some height for it.

[DrPhoton]

Ohnestly, theres no easy way to estimate how light will behave. Some understsnding in light physics will give you some idea, but for the best calculation, the use of a model/simulator would be required. Which there probably are, but would demand accurate data on the light source to be calculated efficiently.

For some guidelines, LED's close together with narrow angle lens such as 60° will converge light more and focus heavily around the center, giving good vertical uniformity but horrible horizontal uniformity. Likewise, if you use LED's wide apart with wide angle lenses such as 120°, light will diverge more and you will get better horizontal uniformity, but worse vertical uniformity. Also the wide spread will cause some additional loss of light through reflection on walls or completely missing the intended canopy.

I think this may be partly the reason for why LED's are hung higher, they dont necessarily produce higher radiant flux, its just that the nature of solid state lighting and design, typically creates a light source that is heavily focused in the center, preventing the light from being closer.

I have always advocated that the ideal light source is one that is wide with narrow reflectors or lenses as this allows the light to be as uniform as possible.
What you will want to achieve is building the fixture as wide as possible (within the constraints of the budget) with the angle of the lens dictated by the size of the fixture. You could even go as far as putting wide angle strings in the center and narrow angle strings on the outside. Theres quite a few options. How you design this should also be built around how high you hang your light source, the higher the hang, the more narrow the directivity. The lower the hang the wider.

At the end of the day it would probably require just some trial and error. But man, the more and more i have thought about it, the more i see how not simple it is. Not that i thought it was easy but the diversity of thinking involved if you really want to do things right. Im sure a half asses build would do ok, but i aint that guy.

[danbwc]

Today is holiday here in my country so I have some free time, I'll see if i can find some numbers having the ViparSpectra as a model. They have a map of umols for different heights and they use the same LEDs than me, but they are 5W not 3W and the lens are 90. I'll see if I can calculate it. Hope the map from ViparSpectra is trustworthy

[Zativa]

A related bit of info: I switched from MH and HPS to LEDs last year and selected fixtures based mostly on price. At the time, that seemed to be the 'Roleadro' series, with a 300W fixture selling for $70 on Amazon. They did exceptionally well during the veg phase, and were MUCH cooler than the discharge bulbs which is very important in my location. Overall, a lot of bang for the buck and I'm still entirely happy with them. My plants definitely like them a lot. Their light looks almost white to human eyes, but actually has several spectral lines.

The one thing they did NOT do well was push plants into flowering mode. Just shortening the hours of light took way too long last time. This season I invested in a couple of obsolete (hence reasonably priced) fixtures with switches for both veg and flower. Adding two of those in their 'red' flowering settings made the transition very fast. Bottom line is you may find it easier to design your homebrew fixtures with the option to switch in extra red (and or blue) LEDs as required. The industry has moved away from this approach, but if it simplifies your circuit design, it may be worth considering.

[Paracelsus]

FYI latest high end LED kits

Rapid is using an assortment of Cree and ChilLED is using 4X125w ChilLED 226 LED board modules

https://chilledgrowlights.com/our-products-services/diy-led-grow-light-parts/diy-led-grow-light-kits/500w-chilled-connect-drive-ready-diy-led-grow-light-kit

https://www.rapidled.com/mass-medical-strains-cxb3590-4-x-4-grow-kit/