DIY LED lighting?

[LondonDragon]

Have a look here Ed if you haven't seen this thread yet:

http://www.tropicalfish.site5.com/tfc/s ... hp?t=79416

Hope that helps, doesn't seem that complicated really.

Edit: One more http://www.aquaticplantcentral.com/foru ... array.html

Test on plant growth using LEDs and PC lighting

http://www.aquaticplantcentral.com/foru ... stars.html

 

[SteveyG]

Hi,
One should use caution when analyzing and comparing effectiveness of various bulb technologies. For example, while lumens are an excellent parameter to use when determining human perception of brightness it is a completely useless parameter when used in the context of plant growth. Lumens is by definition a human perception measurement not a direct light energy parameter. Plants don't photosynthesize in direct response to lumens or to watts for that matter, but instead respond to the quantum energy levels based on photon delivery rate per unit area, also known as Photon Flux Density. This can only be measured with a PAR meter which directly measures the photon flux in units of moles quanta per square meter per second, and of course, is only valid over the range 400nm-700nm. This is referred to as Photosynthetically Active Radiation (PAR).

Whilst of course what you wrote is correct, comparing light sources using lumens is going to give a fairly close idea of the light output if we are comparing white light sources especially when you combine this with the spectrometer graphs, and is going to be the only way you can compare them without buying and testing yourself as there will be very few datasheets that give the flux density of their light sources.

 

[scottturnbull]

Having said all that it should be noted that plants have amazing adaptability and will grow just as well with whatever bulb type we choose, whether a sexy LED or a humble incandescent bulb from isle 9 in Tesco.

Ideally you want to efficiently use the power you're expending. A bulb with a preponderance of green, or other unusable parts of the spectrum, is wasting a lot of energy, from a plants' perspective. From what I gather, a preponderance of red with some blue is most efficient for plant growth. Saying that, I deliberately chose a marine white TMC array because the plant specific array produces a yellow/brown tinged light. Looking at datasheets for comparable pure white LEDs, I see they have a huge blue output. The red frequencies are, by comparison, somewhat attenuated. This isn't ideal, but it's a good compromise of efficiency and appearance.

 

[SteveyG]

Conversely, warm white LEDs are considerably less efficient than cool white LEDs - sometimes up to 40% less. They still use the same die in the LED, but the phosphors are different causing the inefficiency. (white LEDs are usually blue LEDs with a phosphor over the top).

 

[scottturnbull]

Conversely, warm white LEDs are considerably less efficient than cool white LEDs - sometimes up to 40% less. They still use the same die in the LED, but the phosphors are different causing the inefficiency. (white LEDs are usually blue LEDs with a phosphor over the top).

It's still possible they are more efficient from a plant-growth perspective. You're talking about total light output vs current input. I'm talking about output at frequencies plants use most. The blue spike in the datasheet is pretty large for brilliant white, and comes at the expense of attenuated reds. Admittedly warm white doesn't have a spike anywhere near as powerful in red - or any particular frequency, for that matter - but its got good amounts of blue and red.

Nevertheless I'll bow to your experience.

 

[SteveyG]

Out of interest, are you using LEDs as a full replacement or as an addition and do you have any pictures of your set up?

 

[Ed Seeley]

Have a look here Ed if you haven't seen this thread yet:

http://www.tropicalfish.site5.com/tfc/s ... hp?t=79416

Hope that helps, doesn't seem that complicated really.

Edit: One more http://www.aquaticplantcentral.com/foru ... array.html

Test on plant growth using LEDs and PC lighting

http://www.aquaticplantcentral.com/foru ... stars.html

Have seen those Paulo, but thanks for posting. Will help many looking here who haven't (and give me a good place to find them when I want to read them again!!!!). I'm liking the idea of replacing the T6 and PCT5 lighting on my upstairs 180l tank at some point with these as that's a custom built wooden hood and would be easier to do.

To be honest guys the only thing the spectrum will do really is effect how it looks to you. Aquatic plants can use a wide range of light as water signifcantly alters light and most 'growth' bulbs and their spectra are based on terrestrial plants AFAIK. Take with a pinch (pile??) of salt ideas about what colour light will grow plants and algae underwater.

 

[scottturnbull]

Out of interest, are you using LEDs as a full replacement or as an addition and do you have any pictures of your set up?

I'm using them to boost the weak performance of a 15W T8.

The LED array is fitted to the flap of a Juwel Rekord 70.



Close-up of optics and what looks like a current regulator, or something. Apart from a few resistors, there's little else in the way of components visible.


Patchy light at surface with only the LEDs switched on.


Spread of light from the side.


Three of these, 15 x 3W, would provide a good level of light. The light they produce is mesmerising.

 

[Garuf]

You can actually get LED reflectors to improve their light spread, soleu or something similar make them for their Leds and they do improve things quiet well.
I did have the link saved but firefox has deleted all my saved pages without asking...
I did electronics at school and LED's are special in that other than resistors they need very little in terms of electronics to control them once you have a regulated transformer. A heat sink is a useful Idea if you use one in a metal halide style format rather than as a strip, but I would say one would be otherwise superfluous.

 

[scottturnbull]

To be honest guys the only thing the spectrum will do really is effect how it looks to you. Aquatic plants can use a wide range of light as water signifcantly alters light and most 'growth' bulbs and their spectra are based on terrestrial plants AFAIK. Take with a pinch (pile??) of salt ideas about what colour light will grow plants and algae underwater.

While that's true for fluorescents and other traditional lighting, LEDs are capable of producing light at very narrow frequency ranges. The difference between a normal fluorescent and a plant growth fluorescent is minimal, with certain bands emphasised. Look at the spectral characteristics for blue, green, amber and red LEDs on page 9 of this pdf.

 

[ceg4048]

Having said all that it should be noted that plants have amazing adaptability and will grow just as well with whatever bulb type we choose, whether a sexy LED or a humble incandescent bulb from isle 9 in Tesco.

Ideally you want to efficiently use the power you're expending. A bulb with a preponderance of green, or other unusable parts of the spectrum, is wasting a lot of energy, from a plants' perspective. From what I gather, a preponderance of red with some blue is most efficient for plant growth...

Actually this is another popular misconception. You can grow plants fairly efficiently with nothing but green light. As I stated earlier the use of light by plants is based on a set of quantum principles and is not as simple as just what colour the light is. The adaptability of the plant to variation of spectral curves has to do with it's ability to produce auxiliary pigments which have a sensitivity range in between blue and red. These special pigments are actually able to mutate non-blue and non-red wavelengths into other wavelengths or they have the ability to release electrons from the pigment molecule during photon collision and relay the quantized energy on to the chlorophyll to be used in the Electron Transport Chain.

As a result photosynthetic efficiency is a very murky subject which transcends the electrochemical equations of power delivery.

Regarding the use of spectral curves one must again take care. The peaks in the spectral curves are completely irrelevant. Vendors try to fool us with their marketing efforts using these curves, but the spectral energy delivered by the bulb is the area under the entire spectral curve. The spikes shows the relative energy level at a specific wavelength only. Therefore the area under the spike at a given wavelength may not be that much compared with the area under the rest of the curve. Another factor to consider is that higher frequencies produce higher photon delivery rates even though may look dim to us (this goes back to the lumen effect discussed earlier). We can observe that a pure blue bulb will "look" dim and will appear to have poor "penetration", yet it's higher frequency may actually deliver a high PAR profile than a light with a green component and which has a much higher lumen value! There are so many competing principles/factors, some effects negating or enhancing others, that it really is quite impossible to determine photosynthetic efficiency unless one performs specific tests to determine total biomass increase as a function of bulb type and versus total consumed watthours.

The bottom line therefore is that one should just get whatever "looks the coolest" whether it be ripple effects, moonbeams, batman or teenage mutant ninja turtle effects, which will be about as accurate in real plant growth terms as any lumen/watt or power/efficiency analysis one could conceive...

Cheers,

 

[SteveyG]

Thanks for the pictures scottturnbull.

I did electronics at school and LED's are special in that other than resistors they need very little in terms of electronics to control them once you have a regulated transformer. A heat sink is a useful Idea if you use one in a metal halide style format rather than as a strip, but I would say one would be otherwise superfluous.

You don't want to be driving multi-watt LEDs with a resistor or you'll be dramatically reducing their efficiency!!

 

[scottturnbull]

Actually this is another popular misconception. You can grow plants fairly efficiently with nothing but green light. As I stated earlier the use of light by plants is based on a set of quantum principles and is not as simple as just what colour the light is. The adaptability of the plant to variation of spectral curves has to do with it's ability to produce auxiliary pigments which have a sensitivity range in between blue and red. These special pigments are actually able to mutate non-blue and non-red wavelengths into other wavelengths or they have the ability to release electrons from the pigment molecule during photon collision and relay the quantized energy on to the chlorophyll to be used in the Electron Transport Chain.

As a result photosynthetic efficiency is a very murky subject which transcends the electrochemical equations of power delivery.

Can you show me your references?

Accessory pigment Xanthophyll 450-480nm (more or less blue).

Beta-carotine around 200nm (basically ultraviolet).

Chlorophyll a, peaks around 400 and 600 (blue and red).

Chlorophyll b, peaks around 400 and 600 (blue and red).

I think you're overstating the ability of accessory pigments, they have their own unique absorption spectra, and vary between plants. In an aquatic environment, the majority of plants are vegetative green, with a minority of other colours. I don't see accessory pigments - given that for vegetative plants most accessory pigments absorb blue and red - playing the magical role you ascribe to them. Maybe in flowering plants, where pigmentation varies more.

I'd like to see your data. I'm not an expert on this by any means. But a quick search about I struggled to find any accessory pigments in plants which utilise green wavelengths in any noticeable way.

As for electrochemical equations being incapable of grasping biochemical processes, a lot of research is being done using laser scanning fluorescent microscopes. These use exactly the same kind of spectral information to precisely target markers within cells.

aptsys: no problem.

 

[JamesC]

I'd be interested too. All the information I've ever read suggests that plants use mainly red and blue light and reflect green light, hence the reason most plants are green. This isn't saying that they don't use green. Amano has a green spike in his metal halide lamps as he says it is needed, but then a lot of his advertising is just hype.

James

 

[SteveyG]

I've had trouble growing non-aquatic seedlings (chili plants) with just the red and blue spectrum from red and blue high power LEDs. The leaves also ended up a bit pale. I had much better results from white LEDs, but CFLs and sodium lamps still gave the best growth. The plants must have requirements other than red and blue.

 

[JamesC]

Or it could be that the red and blue from LED's are the wrong wavelengths. Grolux tubes are basically all red and blue with vitually no green and they grow plants just fine. Indeed that is what Grolux tubes were designed to do.

James

 

[scottturnbull]

I've had trouble growing non-aquatic seedlings (chili plants) with just the red and blue spectrum from red and blue high power LEDs. The leaves also ended up a bit pale. I had much better results from white LEDs, but CFLs and sodium lamps still gave the best growth. The plants must have requirements other than red and blue.

White are probably easier to deploy, by the sound of things, more like traditional lights. I was just making the point that the spectrum matters more with narrow-band LEDs than with fluorescents.

What components are you planning to drive your LEDs with? I was thinking about trying a L165 opamp as a PMW oscillator, or using a L200 without PWM.

 

[SteveyG]

I'll probably use some Zetex ZXLD1350 and ZXLD1360's which I have somewhere (I've not unpacked all my electronics stuff despite moving house 9 months ago!), but I also have some PIC10F204s which I've been using as (cheaper!) switching regulators.

The plan will probably be to have a bunch of constant current drivers as close to the LEDs as possible, driven by the main controller which I will also be re-building. The controller will also dim the T5s, and control the CO2 solenoid etc.

 

[ceg4048]

I think you're overstating the ability of accessory pigments, they have their own unique absorption spectra, and vary between plants. In an aquatic environment, the majority of plants are vegetative green, with a minority of other colours. I don't see accessory pigments - given that for vegetative plants most accessory pigments absorb blue and red - playing the magical role you ascribe to them. Maybe in flowering plants, where pigmentation varies more.
I'd like to see your data. I'm not an expert on this by any means. But a quick search about I struggled to find any accessory pigments in plants which utilise green wavelengths in any noticeable way.

I'd be interested too. All the information I've ever read suggests that plants use mainly red and blue light and reflect green light, hence the reason most plants are green. This isn't saying that they don't use green. Amano has a green spike in his metal halide lamps as he says it is needed, but then a lot of his advertising is just hype.

Hi guys,
Consider for a moment red plants. Do they not use red? Do they use only green and blue. Clearly the answer is no. The green reflected in green plants is reflected by the most populous green chlorophyll, that's true, but other pigments are mixed in and they respond to the green light. In a world dominated by blue and red the plants can afford to ignore some green but there are environments where green and blue are dominant. In these scenarios the plants will respond by adding the necessary pigments.

There's data out there regarding the performance of auxiliary pigments. There's work by Park S. Nobel in his book entitled Physicochemical & Environmental Plant Physiology Blue and Red light are important in that the varying ratios of the two stimulates certain different functions depending on the ratio value.

Of course the is the trusty Barr Newsletter Light and Photosynthesis which ought to be standard reading.

Besides, beyond the theoretical you actually have it in your power to go out and actually try it. You don't need to build your own rocket ship. Go get a small tank and go get some light bulbs of various colors/types, cover the glass so that you can eliminate the influence of external light and see if the plant grows. Green, blue or red light bulbs, as well as DIY fluorescent bulbs from the hardware store. This is not a big deal. I didn't do scientific tests and I didn't compare dry weights or analyze power efficiencies or anything like that. They were just silly tests to superficially disprove the Grolux and Gucci designer £30 bulb marketing efforts.

What you might be underestimating is the adaptability of plants and the science of pigment molecules. There are dozens of other auxiliary pigments groups such as phycobilin, phycoerythrin and phycocyanin. Some pigments work by responding in resonance to particular wavelengths and by fluorescing thereby changing the wavelengths and passing on their energy to the chlorophyll. Here is an interesting report on studies done regarding this principle but performed in the Red region=> Red Drop and Role of Auxiliary Pigments in Photosynthesis

Cheers,

 

[JamesC]

Can't see anything there that suggests you can grow plants in the absence of red and blue light.

James