LED's, Acronyms, Alphabetisms and confusion: By ModAquatics

revhtree

Owner Administrator
View Badges
Joined
May 8, 2006
Messages
47,602
Reaction score
85,990
Rating - 100%
1   0   0
I have seen many posts asking questions about LEDs, PAR, etc, and instead of answering different posts I thought I would start one to create more confusion. :bigsmile: I am not an expert by any means, but I am really into lighting. The information below is based on my personal knowledge.

The following spectrum's may differ between LED manufacturers. The terminology can apply to different types of lighting.
LED's come in color and whites (generally speaking).

LED-1.jpg

Royal Blue LED by Philips


COLOR LED

The colors concentrate on specific wavelength ranges and the LED's are rated by those wavelengths measured in nanometers. (nm=nanometer)

Ultra-violet (UV) 340-420nm Can't see it at the low end, the upper end is violet. It is dangerous at the intensities that we run and should be avoided.
Violet (V) - 410-440nm Burple :wink:
Royal Blue (RB) - 440-460nm Very Blue. Many corals fluoresce different colors when illuminated by this spectrum. See Picture below.
Blue (B) - 460-490nm Blue
Cyan (C) - 490-520nm Not really used much in aquaria
Green (G) - 520-550nm Good for making green corals pop. Contrary to popular belief, chlorophyll's don't use green very much. Most plants reflect it which is why they appear green.
Amber (A) - 570-610nm Not really used much.
Red (R) - 610-645nm Good for making red pop but not used much
Deep Red (DR)- 650-670 Utilized by chlorophyll to produce color. I am experimenting with this and have seen significant color improvement. Especially when combined with Violet LED's. (Thanks SteveB :D ). Deep Red LED's are very visually powerful and should be used as such.
Anything higher than 670nm gets into infra-red (Heat)

LED20111117_06.jpg

Cool White Philips LED


WHITE LED
White light covers a broader area of the visible spectrum. Therefore white LED's are typically rated by CRI (color rendition index) or Kelvin (color temperature). Because the white light can cover such a large range, we typically refer to a white LED by a general type of white based on where it falls in the Kelvin color temperature range (2000-25,000K for aquarium purposes although it is actually broader). The three white ranges are:

Warm white (WW) - Generally the light has more of the upper warmer part of the spectrum or lower part of the Kelvin color temperature. Typically LED's ranging from 2,500-3,500k fall into this category.

Neutral White (NW) - Middle of the Kelvin range about 3,500-4,500K.

Cool White (CW) - the upper and bluer part of the color temperature 4,500-10,000K

PAR and PUR

The visible spectrum ranges from approx. 350nm to 750nm. PAR or Photosynthetically Active Radiation is Photon (particles of light) radiation that can be used by plants and animals to produce energy. PAR is light energy between 400-700nm. PAR meters measure an average of light that falls within this range. Because it measures an average, PAR meters cannot accurately measure Color LED's since they are only narrow parts of the PAR range. Even White LED's cannot be accurately measured with a PAR meter because how they are constructed. All white LED's are either Royal Blue or Deep Red LED's with a phosphor coating (that is why the white LED's look yellow when inactive). The phosphor glows white but much of the underlying photon energy comes through. If someone wants to try a cool experiment, hold a white LED under a Royal Blue and watch the white LED light up.

I am not saying that PAR meters are not useful. On the contrary, if a PAR meter says that the LED is putting 100 PAR (It is really call PPFD or Photosynthetic Photon Flux Density but we will just call it 100 PAR until I buy a DeLorean), It is underestimating the true photosynthetic energy hitting the sand bed. This is because different corals and plants utilize different parts of the PAR spectrum differently. Color LED's (Royal Blue specifically) can provide more (here it comes, a new word) PUR or Photosynthetically Usable Radiation. PAR is a general photosynthetic range whereas PUR is the specific parts of PAR that are usable by specific organisms.

LED20111117_10.jpg



Important things to know concerning LED's.


Amperage - Unlike many electronic devices that are voltage sensitive, LED's are Amperage sensitive. This is why LED's usually require "drivers". These drivers are really just regulating the current available to the string of LED's that they power. This is critical because if the current goes too high the LED will burn out in a flash of momentary glory. The driver also tries to keep the amperage up to the desired level. This can create a problem if the driver is on before the circuit is complete because the driver will try to raise the current. So when the circuit is completed after the driver is powered on the string of LED's all burn out in a flash of momentary glory. I have done this and it was an expensive lesson. Drivers come in two flavors, Buck (current reducing) and Boost (current boosting). Most of the application that we deal with will be reducing the current which is why we see the term "Buck" driver so often. It is also important to note that the lifespan and efficiency of an LED goes down as more current is applied. Therefore, contrary to popular belief, an LED does not have to be driven at it's maximum current rating to be efficient. Basically, if you want more light and you want to maintain efficiency and longevity, then you should not exceed the manufacturers tested LED levels that match the parameters that you seek.

Voltage - Each LED has a "Voltage Drop". Simply put, the voltage drops a specific amount as electricity goes through it. For example, an average 3W LED has a typical voltage drop of around 3 volts. This is important to know so you can determine how many LED's you can have in a string for a given driver voltage output. So, if you want to run 12 of these led's in a string then you would require 36 volts. Ideally you would want to end up with 0 volts at the end of the string so the driver does not have to expend the remaining energy as heat. This may explain why some of your drivers are so hot. In some cases you can reduce the driver heat (wasted energy) by adding another LED.

Heat - Most forms of lighting radiate heat outward as infra red energy along with all of the other parts of the light spectrum. However since LED's are very specific about the light that they radiate, there is very little infra red energy leaving the LED along with the light it produces. But since the LED circuit is pushing a lot of electrons through a teeny weeny junction (the part of the LED where the magic happens) in the LED, there is a lot of heat generated in that process that must be removed or the LED will stop functioning correctly and will eventually fail completely (and permanently). This is why most folks put a massive heat sink on the back of the LEDS to extract the heat. It is also important to maintain heat conduction to the heat sink as efficiently as possible. Usually the heatsink has a thermally conductive compound between the LED and heat sink mechanism. As amperage to the LED gets higher, more heat is generated and conversely, less heat is generated at lower power. The heat sinking process begins at the LED chip itself. Directly behind the junction of an LED the solder conducts the heat to the substrate. The substrate can be a regular PCB (Printed Circuit Board) with heat vias (holes through the board filled with copper to conduct heat to the back) or an MCPCB (Metal Core Printed Circuit Board - usually made from aluminum to conduct the heat to the back of the board. The LED substrate (PCB or MCPCB) is then attached to some sort of Heatsink material. The heatsink material can either be "Passive" (cooling with convection or simple heat radiation) or "Active" (either a fan blowing air or another cooling medium).

LED20111117_04.jpg

Red LED on PCB with Heat Vias


Myths

PAR is PAR - False. There are lights out there that can put out 1000 PAR at the sand bed but some corals would struggle to grow because the light may not have enough PUR for that specific coral. Deepwater corals don't do well under Deep Red light. This is because Deep Red is filtered out after several meters of seawater. Shallow water coral need deep red to thrive better.

The higher the PAR the better - False. There has not been any peer reviewed scientific evidence that I have seen that shows where PAR values higher than 300 have any growth benefit.

There is a specific LED color combination needed - False. White LED's cover a wide spectrum. But some corals grow better under specific color combinations whereas other corals grow better under other combinations. There is none that cover all efficiently. Ask anyone that has run AI's for awhile and they will testify that RB and CW LED's grow a wide range of coral well enough, and other colors are not always necessary.

The best LED efficiency is achieved by running them at higher amperage - False. I see folks doing this all the time and I don't really understand why. Even the LED manufacturers state that the higher the amperage the lower the lifespan and the higher the wasted energy (converted to heat) I suppose people think that the higher amperage produces more light intensity. Although this is true, intensity can be achieved by utilizing optics.

RBTA-1.jpg

RBTA fluorescing Green under Royal Blue LED's
 

Ron Reefman

Lets Go Snorkeling!
View Badges
Joined
Aug 12, 2012
Messages
9,264
Reaction score
20,822
Location
SW Florida
Rating - 0%
0   0   0
Modaquatics,

I have been doing a lot of learning about lighting in general, the light corals need in particular and the way that leds work. You have confirmed a lot of what I believe to be true (that means you're data is right as far as I'm concerned:wink:). And you provided me with a few technical details about how leds work that I wasn't aware of. For that I say 'Thank you'.

The one comment that hit home to me, because it confirmed my opinion, was this, "There is a specific LED color combination needed - False. White LED's cover a wide spectrum. But some corals grow better under specific color combinations whereas other corals grow better under other combinations. There is none that cover all efficiently." I find way to many people have this strong belief that there is one right answer and all the rest are wrong.

One of the things I learned here is, "Heat - Most forms of lighting radiate heat outward as infra red energy along with all of the other parts of the light spectrum. However since LED's are very specific about the light that they radiate, there is very little infra red energy leaving the LED along with the light it produces." I understand light and physics, so this makes perfect sense to me, I just never heard anybody say it, and I never thought of it! Thanks again.

Ron
 
Back
Top