Table of contents
- What are Watts?
- Leds Explained
- Leds are really difficult to manufacture!
- Chinese Leds
- Another Way Leds Are Different
- Types of Power Suppliers
- How and Why Leds Fail
- When Leds Die
- Who Made Your Leds?
- Take the Alibaba Challenge!
- Why do all the Led Lights look the same?
- There are essentially two types of leds: Indicator Leds and Power Leds
- Power Leds
- Led Wattage Ratings and Why they are Misleading!
1. What are Watts?
This is very important and is a source of a lot of confusion. Wattage (number of watts) is just how much power a device consumes – that’s it! Technically wattage is equal to voltage X current in amps or
Watts = Voltage x Amperage also expressed as W = V x A
So for a 100 watt light running on 230 volts mains power we get 100 Watts = 230 Volts x 0.435 Amps
It has NOTHING to do with brightness, just power consumption!
Most people reading this will have been looking at various companies selling led grow lights and I am betting you have seen statements like this:
- “Our 600 watt light consumes only 300 watts of power!”
- “Our 600 watt light (actual power consumption 300 watts)”
Or harder to spot the description will read:
600 watt led grow light.
Then if you look at the technical specs it will say something like:
- 230 Volts 1.3 Amps
- 120 Volts 2.5 Amps
If you use the formula above (Watts = Volts x Amps) you see that:
- 230 Volts x 1.3 Amps = 299 watts or
- 120 Volts x 2.5 Amps = 300 watts (same thing)
So again the light that is advertised as a 600 watt light is actually only 300 watts! This is not just misleading, it is an outright lie! It is not a 600 watt light, it is a 300 watt light. However even the 300 watts rating is usually misleading. This is the amount of power the whole light consumes, not the amount of power the leds consume. So what if anything is the difference? Well quite a bit! The light doesn’t just contain leds, it contains a power supply as well. Just as a light source such as leds has an efficiency factor, so do power supplies. The very best, high grade Switching power supplies are over 90% efficient whereas the cheapest magnetic ones are only about 50% efficient. This means that out of the 300 watts the light consumes the leds are actually getting between 270 watts and 150 watts – NOT 300 watts!
Some companies use a different method of calculating a power rating. They multiply the number of leds by the wattage class of the leds. So for example if the light has 100 3 watt class (notice I am saying ‘3 watt class leds’ not just ‘3 watt leds’) they will them advertise it as a 300 watt light. This is also misleading as the actual power of the leds would be about 175 watts! To find out why read the ‘Led Power Ratings Explained’ section.
At Plant Photonics we rate our lights by the amount of power the leds consume. It may make our lights look less powerful than our competitor’s lights, but it is the most accurate and honest way to rate them. We also only use the most efficient Switched Mode power supplies to ensure the lowest possible electricity bills for our customers.
The problem is that we are conditioned to associate watts and brightness by a lifetime of dealing with incandescent lights. We all knew that a 100 watt bulb was a lot brighter than a 60 watt bulb. We also knew that a cheap 100 watt bulb was as bright as an expensive one, it just probably wouldn’t last as long! That was because the technology in all incandescent bulbs was the same; a tungsten wire in a glass bulb filled with nitrogen. It was also a very mature technology (over 100 years old) so the best way to make them had been worked out long ago and was not longer protected by patent, so everyone made them the same way. However when you start looking at different technologies for producing light such as fluorescent, Hight intensity Discharge (HID) lamps such as Metal Halide (MH) and High Pressure Sodium (HPS) and LED you find that the same wattage of each type of lamp produces a totally different amount of light. So why is this so? Its because there is another factor to consider which is EFFICIENCY. Efficiency is a measure of how much of the power you put in gets turned into light and how much gets wasted, usually as heat. You could put it like this:
Light Output = Wattage x Efficiency
Incandescent lights had a very low efficiency, they produced very little light for the power and produced a lot of heat. This is why we have all been forced to replace them with compact fluorescent lights (CFL), which are 3 to 5 times as efficient. That is why a 20 watt CFL is a replacement for a 100 watt incandescent.
Unlike the old incandescent lights, led is a new, complex and rapidly evolving technology which is very hard to produce to a high and consistent quality. It is also covered by thousands of patents so the best designs and manufacturing techniques can only be used by the patent holders and the companies they licence.
This is the reason two led lights of the same wattage can produce totally different amounts of light even thought they consume the same wattage – top quality leds are very efficient, producing lots of light and very little heat; whereas poor quality leds are not very efficient, producing little light and a lot of heat.
2. Leds Explained
Leds are different from any other light source. They are solid state devices which work at a sub-atomic level. A detailed explanation of how they work is beyond the scope of this website and really isn’t that important. For an in depth explanation read this excellent article at Wikipedia: http://en.wikipedia.org/wiki/Led
3. Leds are really difficult to manufacture!
Producing them requires growing a thin layer of crystal on a substrate (supporting layer) of synthetic sapphire or silicon carbide. The process has to be incredibly tightly controlled across a whole range of factors, in fact a lot of the steady increases in led efficiency/brightness come not from new advances in technology but from improved quality control in manufacturing. Other increases have come from modifying the structure of the led layer to help photons which get created but then are trapped within the structure of the led layer. This is actually nano engineering and is at the very cutting edge of science. This is why there is such a huge difference between leds manufactured by someone like Cree or Philips Lumileds and some factory in China which has bought some equipment and is churning out cheap leds!
Some more information on the challenges of growing the leds can be found here: http://en.wikipedia.org/wiki/Epitaxy
After the wafer is coated it is cut into thousands of tiny chips. To give you an idea just how difficult to control the manufacturing process is, each of these tiny chips will have slightly different properties, that is the voltage requirement, wavelength and brightness will all be slightly different for each chip!
These chips are then individually tested by machine and sorted into ‘Bins’ according to their properties. Understanding this is quite important, especially if you plan on building your own light as all leds are not created equal; for example the brightness of the same make and model of led can vary by over 100% depending on the bin designation and the voltage required can also vary by up to 50%. This means that the leds from best voltage/brightness bin put out twice the light for 2/3 the power of leds from the worst bin. So if you see some bargain price leds from a good manufacturer on a website, make sure you know what the bin code is before you buy – they may not turn out to be such a bargain after all!
All quality led manufacturers have the bin codes listed on their website. An example document for the Cree XP-E family of leds can be found here: http://www.cree.com/led-components/media/documents/XLampXPE.pdf
*Plant Photonics only uses leds from the brightest and lowest forward voltage (most efficient) bins in all our lights.
5. Chinese Leds
As far as I know all led grow lights currently available (except those made by Plant Photonics) are made using Chinese leds. If giant companies such as Cree and Philips Lumileds which pioneered the development of lighting class leds have such difficulty producing quality leds consistently, can you image what sort of quality some company in China with no experience of led manufacture produces? I have purchased samples from over a dozen Chinese manufacturers and tested them. I found the following:
- All were poor quality.
- None came anywhere near their rated/advertised brightness or efficiency.
- They gave only 33% to 50% of the light of a quality led while drawing up to double the power.
- Some didn’t work at all.
- Some blew after a short time, some failed after weeks or months.
- There was a huge range of wavelengths, brightnesses and voltage requirements in the same batch from the same manufacturer.
This shows a complete lack of binning and quality control. Many were fraudulently labeled as top quality brands such as Lumileds or Cree.
I think one thing says it all about Chinese leds – the Beijing Olympics was a hugely important event for China. Much of the lighting was done with leds. No Chinese leds were used at all, the contracts went to Cree and Philips Lumileds!
Like with everything else the Chinese are exploiting the popularity and high price of quality leds by producing counterfeit copies of top brands. Please see the ‘How to tell who really made your leds’ section for information on how to identify fake leds. There are several discussions on counterfeit Chinese leds here: http://www.candlepowerforums.com/vb/forum.php
*Plant Photonics uses only leds and chips from the top manufacturers such as Cree, Philips Lumileds, Bridgelux and Ledenjin in our lights. We DO NOT and NEVER WILL use any Chinese leds.
6. Another Way Leds Are Different
Most types of lighting are what are know as ‘linear devices’ that is if you increase the voltage by say 10%, the current they draw will increase by 10% and the brightness will increase by roughly 10% as well. Leds are different – they are non-linear devices. A small increase in voltage causes a large increase in current, so a 10% increase in voltage may cause a 50% increase in current and goodbye led!
LED Graph Cree XP-E
This diagram is from the Cree XP-E datasheet. You can see how quickly the current goes up as the voltage is increased. The led lights at 1.8 volts, reaches 350mA at about 2.1 volts and full power (700mA) at 2.3 volts. Increase the voltage to 2.5 volts and the led will blow! This is why it is important to use current limited power supplies (see Types of Power Supplies, below), which monitor the current going through the leds and adjusts the voltage to keep the current at the right level.
7. Types of Power Supplies
There are 3 basic types of power supplies which are used to power led lights. Only one of them is safe!
1. Current regulated power supplies: These are the correct type to use with leds. The current is set to the correct value, for example 700mA for 3 watt leds, and the power supply then adjusts the voltage to maintain this current exactly. If a led shorts out the power supply will instantly adjust to compensate – protecting the remaining leds.
2. Voltage regulated power supplies: These can be used but are not a good idea. These put out a constant voltage and are usually used with a resistor to match/lower the output of the power supply to the correct voltage for the leds. There are two problems with using this type of power supply. Firstly if a led fails the power supply does not compensate and the rest of the leds may blow. Secondly the voltage the leds need CHANGES over the life of the led! During the first 200 to 300 hours the leds undergo a process known as burn-in, and the voltage required to run them DECREASES by about 10%. This means that while the leds may draw the correct current when the light is built, over the next few weeks the current will slowly increase and the leds will either fail or have their lifespan severely cut!
3. Non regulated power supplies: Unfortunately these are used a lot in led lights. These can be an old fashioned magnetic ballast (transformer) or most often just a device (a rectifier and a capacitor) to change normal mains AC voltage to DC. This is why led lights usually come in certain multiples of leds – that number of leds draws 110V or 220V so they can be run directly from the mains. Unfortunately as well as having the same problems as voltage regulated power supplies, they have no protection against voltage spikes or fluctuations in the mains voltage.
*Plant Photonics uses top quality current regulated power supplies with full input and output protection in all its lights.
8. How and Why Leds Fail
Generally leds don’t really fail the way an incandescent light bulb does. Instead of suddenly blowing, they slowly fade in brightness over a very long period. The usual method or rating system used to define the life span of leds is L75 (the most common) or L50 given in hours. This is the amount of time before the light output of the led drops to 75% or 50% of the original. Quality leds have a L75 of at least 50,000 to 70,000 hours. That’s 16 years at 12 hours a day! However the lifespan will be shortened greatly if the led is not cooled enough. Good cooling is essential to get the maximum life from leds. Heat is the biggest enemy of leds!
*This is why Plant Photonics lights are designed to use the whole casing as a massive heat sink, and why we spread the leds over a large area rather than concentrating them into a small area like other manufacturers do. The leds in our lights run far cooler than those in any other light in the world.
9. When Leds Die
When leds do blow they can either blow ‘open’ or ‘closed’ (also known as ‘slagging’). If they blow ‘open’ no electricity can pass through them and as leds are usually connected in a long ‘string’ all the leds in that string go out. If they blow ‘closed’ they pass electricity perfectly, so the rest of the string stays lit – which can be bad news! Normally each led absorbs some of the voltage going through it, usually 2.4V to 3.7V per led. When they blow closed they don’t absorb any voltage, which means the voltage to each of the other leds increases. As mentioned above, a small increase in voltage means a big increase in current through the remaining leds. If the light has a current regulated power supply it will detect the increased current flow and automatically adjust its output to protect the rest of the leds. If the light doesn’t have a current regulated power supply (and as far as I know none of them do) it will often cause all the other leds in the string to blow like a string of firecrackers! Even if the remaining leds dont fail straight away, the increased current will greatly reduce the lifespan of the remaining leds, usually causing them to fail in a few days or weeks.
*This is why Plant Photonics uses top quality current regulated power supplies with full input and output protection in all its lights.
10. Who Made Your Leds?
It is increasingly common to see led grow lights advertised as being made with leds from a top manufacturer, usually Cree or Bridgelux. This is because by now most people are aware of the poor quality of Chinese leds. Unfortunately none of them really do! It should be easy to look at a photo of the leds and identify who really made them. Unfortunately in reality it isn’t that easy due to the fact that all the top manufacturers don’t just sell complete leds, they also sell the chips to other companies. These companies buy the chips and package them into their own housings, so a led may have a genuine Cree chip and perform just as well as a led bought directly from Cree but look completely different from a distance. So how can you tell? Well the key is not to look at the led from a distance, but to get up close and look at the chip itself.
If you look closely you will see a pattern of very fine gold lines on the surface of the chip with 1 to 4 very fine wires attached to it. This is called the current spreader or voltage spreader. It spreads the electrical charge as evenly as possible over the whole surface of the chip to maximise light output. If you just attach the wire carrying the electricity to a single point or small area of the chip, only that bit will give off light, greatly reducing the brightness. A general rule is that if this pattern is a simple X or * shape and or only covers part of the chip it is a Chinese led! Good quality leds have a complex pattern like those shown below. Even better, each manufacturer has its own design for these and they are as distinctive as a fingerprint, allowing you to identify who the manufacturer really is! If you buy a led grow light from a company who claims they are using top quality leds and in reality they are Chinese leds (and they all are), demand your money back or depending how you paid, contact your credit card company or Paypal and stop the payment!
11. Take the Alibaba Challenge!
The biggest wholesale website for Chinese goods is Alibaba www.alibaba.com. Just type in the words ‘led grow light’ into their search and you will be quite surprised at what you find. I have just done so and the search returned a staggering 103863 results! You know those lights that claim to be made by a company in California or Amsterdam? Or all the ones who claim to use Cree/Bridgelux etc leds? You know the ones who claim to have done so much research to produce their ‘unique’ product? I guarantee that if you look hard enough on Alibaba you will find them; they are ALL made in China with Chinese leds! A good tip is to look at the pattern of blue or white leds on the light you are thinking of buying and then look for the same pattern on Alibaba.
12. Why Do All the Led Lights Look the Same?
Here’s a little secret, none of the other led grow lights on the market started out as grow lights! The first on the market was the famous (or infamous) UFO light. This was actually a red stop light with some blue leds added in. The case is just a compact fluorescent light (CFL) fixture. They usually had no power supply, just a rectifier and capacitor to change mains AC to DC. The newer and more powerful lights on the market today are actually based on 120 watt led street lights, once again placed in fluorescent light fixtures! That why they all come in multiples of the basic wattage, and if you look closely at the photos of the leds in the larger lights you can see they are made of several smaller units placed side by side. That’s because no-one makes 600 watt street lights! There is one other problem with this approach, many of the circuit boards were actually designed for 1 watt leds. Although they can handle the power demands of the 3 watt leds (just) most grow lights use, the heat sink wasn’t designed to handle the extra heat, so the leds run very hot. This is one of the reasons for the large number (up to 10!) noisy fans these lights use.
13. There Are Essentially Two Types of Leds: Indicator Leds and Power Leds.
Indicator leds are the small plastic (actually resin) leds usually used as indicators such as a ‘power on’ indicator. These are now made in quite powerful versions, some with up to 4 chips mounted in the casing, it is even possible to buy led grow lights made using this type of led. Unfortunately they are NOT suitable for this type of use. The actual light output is very low compared to power leds and they suffer from a major problem – heat. The epoxy they are encapsulated in is a very effective thermal insulator and completely surrounds the chips. If run at a fairly low power this is not a problem, but when run at maximum the heat is sufficient to cause the led chips to deteriorate quite rapidly, making the output drop of to useless levels. Lights made with these leds are essentially expensive toys only suitable for growing a (very) small house plant for a child’s science project.
14. Power Leds
These are also known as lighting class leds. They range in power from 1 watt to around 100 watts, although anything over 10 watts are usually multiple smaller chips mounted in a single large package. The power led was first produced by Philips Lumileds in 1999 when they brought out the first led capable of running at a continuous power of 1 watt. Currently most grow lights are using 3 watt leds for two reasons: 1) They now offer the best price performance ratio 2) People have now wised up to the fact that leds are not magic and you still need a significant amount of power to successfully grow and flower plants. You just fit that many 1 watt leds into a reasonable sized light!
15. Led Wattage Ratings and Why They are Misleading!
You have all seen lights with 1 watt and 3 watt leds. You have also seen lots of adds for lights which contain 100 x 3 watt leds and claim to be 300 watt lights. Pretty straight forward yes? Well actually it isn’t! Not only do leds not really draw the power you would think they do from their mane/rating, different coloured leds with the same rating and from the same manufacturer actually draw different amounts of power. So why are they called 3 watt (or whatever, its the same for all power ratings) if they really aren’t? If you have read the earlier section ‘Another Way Leds are Different’ you know that leds need to be driven to a certain current level, not a certain voltage level like other lighting devices. Imagine what it would be like if different led manufacturers all produced leds with different current requirements, if for example Cree made leds that required 600mA, Philips Lumileds 700mA, Bridgelux mA750 etc. Power supply companies would have to make power supplies for each of these ratings and you wouldn’t be able to mix leds from different companies in your product. It would not only be a nightmare to work with them, it would greatly increase the price of the power supplies as each would be sold in much smaller quantities.
So the manufacturers got together and created standardised power levels of 1, 3, 5 etc. watts. When they created these standards, it is quite likely that the name of each rating was pretty accurate and a 3 watt led really did consume around 3 watts of power, however since then the efficiency of leds has increased dramatically and the voltage required to drive the led to 700mA has dropped. Today the average 3 watt led actually consumes about 2.1 watts. Now remember I said different colours consume different amounts of power? The reason is that the different colours use different materials and require different voltages. I will just cover blue, red and white here, the following link to Wikipedia gives the full range of colours, voltages and materials.
Note – the value they give for red is a little on the low side, the value I use is a bit more realistic. http://en.wikipedia.org/wiki/Led#Colors_and_materials
- Red – 2.4 volts so actual wattage at 700mA is 2.4 volts x 0.7 watts = 1.68 watts
- Blue/Royal blue – 3.4 volts so actual wattage at 700mA is 3.4 volts x 0.7 watts = 2.38 watts
- White – 3.4 volts so actual wattage at 700mA is 3.4 volts x 0.7 watts = 2.38 watts
The reason the figures for Blue/Royal Blue and White are the same is that a white led is actually a blue led which has been coated with a material called a down-shift phosphor. This absorbs the short wavelength blue light and ‘down-shifts’ it and emits a mix of longer wavelengths (different coloured light) to produce white light.
Back to our example of the ‘300 watt grow light’ with 100 x 3 watt leds. Assuming it has 80 red and 20 blue leds (an average mix) you have:
- 80 red leds x 1.68 watts = 134.4 watts
- 20 blue leds x 2.38 watts = 47.6 watts
- Total 134.4 + 47.6 watts = 182 watts
There is a big difference between the 300 watts quoted in the add and the real figure of 182 watts, is is only 60% of the power you think you are getting (and paying for)!