Let’s Pretend it’s Science (Final Update)

Six weeks after transplanting the lettuce seedlings I am going to call the experiment done. The plants themselves are crowding their grow areas and I think they are mature enough to draw something like a conclusion. 53 days have passed between the time I planted the seeds (Jan. 14) and this final update, this variety is said to be mature is as little as 55 days from germination, I doubt a further 7 -10 days will make much difference.

The plant growing under the 9 “Grow” emitters was stunted in the first updates but has basically recovered by this point.

Picture 1


Picture 2

6Plants Details

Picture 1 shows all six plants in their individual growing chambers and Picture 2 shows a detail view of the plants growth. The first four plants are notably taller than the final two but while it may not be clear from the photos, the final two are much denser and have a profile more like what is to be expected from this variety. Finally while none of the plants developed anything close to the depth of colour that this variety produces when grown under natural light the plant grown under the 6 Red and 3 Blue emitters had a noticeably deeper colour.

Additional Photos at the end.

Conclusions such as they may be..

First and foremost I find that I am quite disappointed by the results from the “grow” emitters, not least because I believed the manufacturers hype and had bought over a hundred of them for my next project. All four of the plants grown under the Grow and Cool White emitters are taller and more loosely grown than is typical for the variety, while I wouldn’t go so far as to call them “leggy” they are not the densely compact shape I would hope for or expect from these plants. (some of the plants required a coat hangar “prop” to hold them up in the photos) If I’m forced to choose I would say that the Cool White Emitters were marginally more effective than the Grow type. Both these types of emitter are “full spectrum”, they use a Blue or Deep Blue emitter to energize a phosphor like that found in a fluorescent light. It may be that there is energy lost in the process of energizing the phosphor or it may be that some of the energy is converted into wavelengths of light that are less useful to the plants. Whatever the reason for the difference the two lights built with the narrow band emitters produced better, or at least more typical plants.

There is one caveat I would like to make, both the grow emitters and the lights made from the narrow band emitters suffer from a similar problem, they give off a pinkish purple colour that is very hard on the eyes. This is not a big problem if you are using them in a closed environment like a grow tent but it is a problem if you are growing in a room that you may want to use for something else at the same time. A light built from a combination of the different white emitters could be used anywhere, while there would be a small sacrifice in energy efficiency I don’t know that it would be critical in most cases.

Ultimately however the best results came from the lights made with multiple narrow band emitters and of the two the one with the 2:1 Red:Blue ratio out performed the one with the 8:1 ratio.

The next big project is going to be a pair of 90 emitter lights, but the task is tedious enough that I wont be using the Grow emitters, so it will have to wait until I can get the emitters I want via ebay.







LED Experiment Week 4 Update.

Week One


As noted earlier the plant under the 9 grow emitters seemed to suffer from transplant shock, the others are all doing well.

Week Two


At two weeks into the experiment the plant under the 9 “grow” emitters is still stunted compared to the others but it is recovering. At this point I am fairly comfortable blaming transplant shock rather than the emitters for it’s appearance. To support this the plant under the 6 “grow” and 3 Red emitters appears to be one of the more vigorous plants. Also at two weeks it appears that the plant under the 9 Cool-White emitters is lagging in growth and finally the plant under the 6 Red:3 Blue emitters is starting to show a greater depth of colour than the other five plants.

Week Four


After four weeks the plants have become large enough that I don’t want to remove the partition in fear of damaging them when I replace it. Unfortunately this makes for a rather poor photo. For the update on week six I think I will remove the plants and photograph them individually.

I don’t want to make any significant observations at this point, not least because the photograph from the top down angle isn’t the best. That being said the photo does show that the stunted plant has recovered but is obviously still lagging in growth, and the plant under the 6:3 Red:Blue light continues to show a greater depth of colour than its peers.

My First Hydroponic Carrot


It’s hard growing carrots in a hydro system, at least for someone as impatient as I am. Unlike Lettuce or Peppers I can’t see them to know what is really going on, it’s enough to drive me a bit nuts. All those weeks spent using up space under the grow lights, all that nutrient solution and I still have no idea if it is working out..

Well today I caved, even though I’m still about three weeks from the theoretical harvest date I pulled one to take a look … I’m inordinately pleased with this. (The variety is Cosmic Purple.)


Okay so soon the paranoia will creep back and I’ll start to worry that this was a one off but for now I’m going to remain pleased.

Buying an LED grow light Part 1 of ?

TL;DR – When buying an LED grow light compare the actual power consumption at the wall to the stated or theoretical power consumption of the chips. the closer the two levels are the better.

I’ve put together little hydro systems for a couple of friends and relatives, and for some reason they don’t want to spend the time to make their own LED lights preferring to buy pre-made despite the fact that homemade are typically about the same price and a big pain in the ass to make.

Buying LED grow lights can be a pain as well, there are a lot of different styles and types each has it’s own set of Pro’s and Con’s. Obviously you want the most “Bang For Your Buck”, but it is very hard to compare the output of two different lights. Ideally the light manufacturers would agree to use a standard measurement and methodology but sadly they don’t. In the absence of a real standard the most important thing to be aware of is that when a manufacturer refers to a light as being a certain Wattage that statement probably has nothing to do with the actual power consumption and little to do with the brightness of the light.

The reason for it goes right back to the chip manufacturers themselves, leaving aside for the moment COB or Chip On Board lights, the 1, 3 and 5 Watt designations used on LED chips are, or have become, class descriptions not actual measurements of power consumption. The criteria that determines the class of the chip is the forward current at which it is driven, 1Watt chips are typically driven at 350mA, 3Watt chips at 700mA and 5 Watt chips are driven at 1200mA (1.2 Amp)* Manufacturers (or those doing the marketing) usually just multiply the number of chips in the light by the “Wattage” of the chips and refer to that as the Wattage of the light. (Though some have started to refer to these ratings as Model Numbers or Series Numbers in their fine print)

While some 1 Watt chips actually consume 1 Watt it is often impossible to reliably drive 3 or 5 Watt chips at this stated wattage. (See Table 1.) Neither Table 1 nor Table 2 attempt to represent every chip from every manufacturer, these are typical or average values only.

[EDIT Feb. 12 for clarity: I don’t mean to say that no chips actually consume the power they are rated for, some can indeed be driven at a high enough current to make their rating but they are regrettably not typical.]

Table 1


Unfortunately while these numbers are already misleading the manufacturers don’t even power the chips to the full forward current that determines that chips class. By purposely under-powering the chips the manufacturers reduce the heat generated, increasing the chips reliability and extending their life. Under-powering the chips would also allow a manufacturer to use inferior quality chips should they so choose. [To be fair the often most efficient way to drive a chip in terms of light produced / energy consumed is to drive it at a point bellow the rated current, but since efficiency is not reflected in any of the marketing I wont be addressing it.]

Ideally grow light manufacturers would list the forward current at which they drive their chips, and while I’ve seen it listed it is very rare. In most cases in order to accurately evaluate a light you may be thinking of purchasing you should dig a bit deeper in to the spec. sheet. Most manufactures will list the actual power consumption of their lights, as general rule of thumb (and this applies to all types of LED light) the higher that number is, as a percentage of the claimed wattage, the better. Even so, don’t expect to see values near those found in the descriptions. As shown in Table 2 (Bellow), a hypothetical grow light using 100 3Watt chips or 60 5Watt Chips, and having a 5.5:1 Red:Blue ratio might have a typical consumption of around 160Watts, assuming chips were driven at the Typical forward current for their class.

Table 2


Currently on ebay you can find two virtually identical “300 Watt” grow lights, one with an Actual Consumption listed as 140W +/- 3% and one listing 100W +/- 3%, that represents either 87.5% or 62.5% of the theoretically available power.

Of additional interest…

Different Colour LED chips are made from different materials and have different potential Forward Currents, a good wikipedia article and a table listing each can be found here:

LED Colors and materials

* 5Watt chips are even more confusing, some as above, rely on a higher froward current but some are built like the COB (Chip On Board) lights with two or four emitters on the chip. The result is a higher forward voltage or forward current created by tying multiple emitters together in parallel or in series.

Let’s Pretend it’s Science Chapter 1, Update 1

After one week under the lighting set up 5 of the 6 plants appear to be flourishing.one-week

Okay so it is very early days yet but the plant under the 9 Grow emitters seems to be significantly lagging behind the others. I expect it is simply a bit of transplant shock, at least I hope so, since I already bought a bunch of these for my next project. (I am planning to try and build a light with 90 emitters) The plant under the 6 Grow and 3 Red emitters is doing well and that gives me some hope that I haven’t completely wasted the money spent on the grow emitters.

To answer a question I’ve had a couple times, these LEDs and their power supplies were all sourced via ebay from china. The main criteria in the decision making process was price. The LEDs are all “3Watt” LEDs and the drivers are constant current drivers rated to handle up to 18 3Watt chips wired in series at a current of 650mA.

I plan to post a more detailed build explanation in the near future… (but I am going to have to make sure that I am not wasting my time with the grow emitters)


Let’s Pretend It’s Science! (Chapter 1)

Let’s Pretend it’s Science!

I’ve built a number of my own LED grow lights, trying out a number of different styles and designs, I’ve also bought a few from China via Ebay. Leaving aside for the moment why I chose the style of system I’ve used (3 Watt emitters) there is one question that appears common and affects all types of LED grow lamps – colour (color) temperature and mixture. In the process of trying to best understand what works and why I’ve read a lot of different papers, a number of them contradictory and some just plain wrong.

I’m not attempting to set myself up as the expert, I don’t have the background nor the facilities to to turn this into real Science but I have put together an experiment that I think will be interesting to anyone who wants to grow with LED lights.

To begin, for clarity I use the term emitter to refer to the individual LED chip, an LED light uses multiple emitters. To make things slightly more complicated there are two basic types of LED emitters. Single colour emitters produce a fairly narrow band of light with a very pronounced peak at a specific wavelength these wavelengths are in the range of 20nm wide. The other basic type are “full spectrum” emitters that use a blue, narrow band emitter, to energize a phosphor much like that found in a fluorescent light. The “full spectrum” spans roughly 300nm and the individual phosphors can be tailored, most are some version of white but there are “grow” types available, all of them however produce “extra” blue light from the original emitter.

What I’ve attempted to do is set up 6 different “lights” using 9 emitters each, the different lights attempt to represent the most common commercial and or home build patterns.


I started twelve seeds of a lettuce variety called Merlot on January 14 2017 on the 26th I chose the six closest to the same size and moved them to net pots and placed them in the 10 gallon Rubbermaid DWC container.


When grown outside in natural light the plants resemble this picture. The photo is from West Coast Seeds the vendor and used without their knowledge or permission.


The lights are positioned 16 inches over the tops of the plants, and are set for a 12 hour day. The plants are in identically sized compartments and isolated from contamination by outside light by wrapping the whole thing with panda film.


The nutrients in the container are Botanicare PureBlend Grow mixed at approximately 1/2 strength.



Beginning in the upper left an moving clockwise…

The first light closely mirrors the 9:1 Red:Blue ratio found in many of the inexpensive currently available Chinese LED grow lights. These are sometimes referred to as Veg/Bloom lights partially because higher levels of red light are associated with flowering.

4 = 660nm Red 2 = 640nm Red 2 = 620nm Red 1 = 450nm Blue

The second light, with a Red:Blue ratio of 2:1 is closer to the 4.5:1 ratio of an older Chinese made light I have. I have exaggerated the Red:Blue ratio to see what the effect may be.

2 = 660nm Red 2 = 640nm Red 2 = 620nm Red

 1 = 450nm Blue 1 = 465nm Blue 1 = 475nm Blue

The third light is something of an experiment for me, all nine emitters are a new “GROW” type, the manufacturer claims a spectral output designed specifically for growing and a range between 380nm to 820nm.

The fourth light is made up of 6 of the above mentioned Grow emitters augmented by 3 Red emitters.

6 = Grow 2 = 660nm Red 1 = 640nm Red

The fifth light represents a fairly common home build style where Daylight or Cool White emitters are paired with supplemental Red emitters. In this case I used a 2:1 White:Red ratio. Similar to the fourth light except the Grow emitters  were changed to Cool White.

6 = Cool White 2 = 660nm Red 1 = 640nm Red

The sixth light is entirely made up of Cool White emitters, these are by far the easiest and cheapest emitters to access.

Day one under the lights, panda film removed for the photo.


                      Limitations:   (or some of the many reasons why this isn’t really science)

For this to be really scientific I would have had to produce many more than just the one plant under each type of light. I also should have used clones from a single parent plant to eliminate any genetic differences. The biggest drawback though is that I’ve only got 9 emitters per light this limits the number of lighting options available, many of the commercially available grow lights use more bands of light than even the 6 used in light number 2 (often 7-9), I’ve been using 12 bands for the lamps I build for myself.

I will be providing updated photos as growth progresses.

As a follow-up to this experiment I may grow dwarf tomatoes either under the same light or one configured to use 12 or 18 emitters.