We take a closer look at both dumb and smart LED bulbs.The traditional light bulb – or incandescent lamp if you will – was slowly but surely phased out during the last decade.The point was to replace old and energy-wasting technology in order to lower total electricity consumption in Europe.The EU's move was not immediately well received everywhere, and there were some good reasons for that.The alternatives in the form of energy saving bulbs, halogen bulbs and LED bulbs were typically more expensive, uglier and gave a less natural light than the old bulb with filament.But along the way, fortunately, LED technology – which is also the most energy-efficient – ​​has gone through a formidable maturation process, both in terms of price, functionality, selection and appearance.Furthermore, the LED bulbs have been given the opportunity to become "smart", which for many can be the first step on the way to a smarter home.In this guide, we will take a closer look at the technology behind LED and smart light bulbs.Let's start with the basics.Most of us don't think much about LED (short for light emitting diode) on a daily basis, but today this can be considered as standard lighting.And then we don't just think to light up ceilings and walls, because LEDs are also backlights for modern screens - whether we're talking about a tablet or the new, huge TV in your living room.The exception is naturally screens built on OLED, as it is a technology that does not require a backlight.In any case, LED has become such an important part of our everyday life that the inventors of the technology behind the blue LED light received the Nobel Prize in Physics in 2014.It is the blue LEDs that give us normal, white light - simply by covering the diodes with a layer of phosphor.This makes them look yellow or orange, but ensures that the light is not too blue or "cold".A composite illustration showing part of the spectrum that can be obtained from white light - from warm on the left, neutral in the middle to cold on the right.Note that our eyes and brain adjust to the light, so in reality it is not perceived as orange and blue as this.As you have probably gathered, it is the case that different light sources can have different properties.If you take a look at the packaging an LED bulb comes in, it is quite possible to form an idea of ​​the kind of light you get from it.Note three things in particular:Lumen: The efficiency of the light source is given in lumens (lm).The higher the number, the more light it emits.Standard LED bulbs are normally between 200 and 1100 lumens.A well-known rule of thumb says that if you multiply the classic wattage from the "old days" by ten, you get roughly the same number in lumens.But really, it's a pretty bad rule, and it's been so long since the incandescent lamp was phased out anyway that it's high time to learn the new system.It might be a good idea to take a look at the light source's package insert.Color temperature: All visible light has a certain color temperature, and this is usually stated in Kelvin (K).The temperature says something about how red (warm) or blue (cold) the light is - the lower the number, the redder and more "atmospheric".Lighting sold for normal indoor use typically varies between 1500 K and 9000 K. The classic incandescent bulb often had a color temperature of approximately 2700 Kelvin, so for many LED bulbs this is the standard.Ra index: Most light sources have a so-called Ra index or color rendering index, given with a number between 1 and 100. This number says something about how well the light reproduces colors as naturally as possible, and then higher values ​​are better.In most cases, we want a figure of 80 or higher.At the same time, the Ra index is not a good and uniform way of measuring color reproduction, as two bulbs with the same measurement number do not necessarily reproduce the same colors in the same way.Using LED as lighting has, as mentioned, developed a lot over the past few years, and if we look at the traditional "bulb shape", there are mainly two types of LED technology that are used.SMD: These letters stand for surface mounted device, and a typical characteristic that this technology is in use is a rather large and heavy "base" above the threads at the bottom.In some cases, this base part is larger than the part of the bulb that actually lights up.SMD bulbs need effective cooling, and they usually solve that with the thick and heavy base above the threads.If you can see the individual LED chips in an SMD bulb, these are usually relatively few and large.To put it this way: If the light bulb does not really resemble an old-fashioned light bulb with a filament, it is probably SMD that has been used.COB/COG: A newer and even slightly more energy-efficient LED technology goes by the name chip on board, which in turn has been given a variant called chip on glass.The technology allows more diodes in less space, and many people will become familiar with this form of LED through so-called filament bulbs.Many such large filament bulbs are advertised as "vintage" by the shops, as they tend to look like traditional incandescent lamps.For the G9 bulb with SMD technology on the left, we can easily count 7 LED chips under the plastic shell.For the bulb on the right, at first it looks like it just has a big "LED field", but this is actually a long series of small diodes made with COG technology.In the macro image on the right, we can both count them and see that they are connected to each other.At the same time, we have also received light bulbs - both large and small - that have adopted this newer LED technology without looking very exclusive for that reason.The nice thing about SMD-LEDs is that each individual LED chip can have a red, green and blue diode, which in turn means that in practice it is possible to reproduce all possible colors by adjusting the strength of the individual diodes.On many LED strips, it is easy to see that the individual LED chips have several diodes.This is what makes the "RGB lighting" that is pushed into everything these days.Otherwise, it is simpler, cheaper and better to make white light by only using blue diodes and covering these with phosphors.Different "colour mixes" in the phosphor then give us light with different color temperatures.SMD bulbs can also have an adjustable white color temperature.These are then equipped with several blue diodes covered by different phosphor mixes which give them different Kelvin values.The color temperature can then be varied by adjusting the strength of the different diodes.The large and heavy base of these bulbs does its part to keep heat generation at a decent level, as high temperatures cause the LED chips to have a much shorter lifespan than they should have.Early SMD bulbs often had external heat sinks.This bulky base, and the fact that the LEDs on these bulbs tend to only sit on top, also limits the angle of the light coming from them.In a normal standing lamp, they will shine over an angle of 250 degrees or less, meaning that part of the area "under" the bulb will not be illuminated directly.Typical spot lights naturally provide light over an even smaller angle, but this is also part of the point of this type of lighting.With low brightness it may be possible to see the individual diodes in a filament.This is a relatively new addition to the lighting market, and here we have LED bulbs with something reminiscent of thick, old-fashioned filaments.Such a "thread" is called a filament.This filament is simply a series of small LEDs surrounded by glass, which in turn is covered by phosphor.Although the filament actually has many individual diodes inside, these are so close together and shine so intensely that it is basically perceived as a uniform glow.Only when we dim the bulb down does it become easy to see how it all fits together.The disadvantage of filament bulbs is that it is currently not possible to experiment with RGB lighting.In most cases, we also cannot adjust the color temperature within "white" light.This is determined at the factory by varying the "colour mix" in the phosphor that forms the outermost layer of the filament, alternatively by using colored glass.Light bulbs from Ledvance and Ikea.The former is a COG LED bulb with four filament wires and a real glass dome.Ikea's COB-LED variant has more "threads" and shines more brightly.For good enough cooling, the bulb has then been given such a large base that we more often see on SMD bulbs.In addition, we can see that Ikea has used two different phosphor mixes, which again means that the bulb can give us different color temperatures.If you want warm mood lighting at one moment and colder work lighting at the next, you will therefore quickly end up with bulbs based on SMD LEDs, although there are also exceptions.In any case, development here is fast, and we will probably see more filament bulbs with more and better adjustment options during the year.Although the rows of small LEDs make the filament resemble incandescent filaments, the technology is not plagued by heat as much as SMD.Good cooling is still important, but can be ensured to a greater extent through good placement of the filaments and the use of helium gas in the glass dome to conduct the heat better.Smart filament bulbs from Philips Hue, Ledvance and Calex.The latter has filament threads with different phosphor mixes, which makes it possible to adjust the color temperature.Therefore, many filament bulbs are made of glass, and often do not need cooling solutions that limit the design.In this way, the filament has almost given the light bulb a "new spring" with its many sizes, shapes and colored glass surfaces.Without a large base at the bottom, the lighting angle is also larger than with an SMD bulb – it can be closer to 360 degrees.Until now, we have mainly discussed LED lights with the classic bulb shape, but one of the great advantages of this technology is that we do not have to limit ourselves to this at all.In many cases, it can actually be more practical or applicable with lighting in other shapes and sizes, and with LED it is really easy to create strips or entire panels that can light up everyday life.The reason why LEDs come in bulb form at all doesn't really have to be anything other than old habit.But at the same time, this form has also withstood the test of time very well, so there is nothing to suggest that light bulbs will go out of fashion.In any case, the result is that there are more and more possibilities and good alternatives in lighting.The basic technologies that we have discussed further up in this guide are common to all LED lighting.At the same time, there is one important thing we have come across that requires it to be possible to communicate with the lighting - in other words, that it is "smart".Because even though "dumb" light bulbs can be turned on and off with the light switch on the wall, and in many cases can be dimmed, they cannot change color temperature in step with the sunlight or switch to glowing green when the bathroom is finally free.If you want to have such options, the easiest thing to do is to go for "smart" lighting.This does not mean that the bulbs have more intelligence than ordinary light bulbs, but they can be controlled remotely via a wireless network.Then you can control things like colors and temperatures with an app on your mobile.Two home hubs: Athom Homey and Samsung SmartThings Hub V3.If you also set some type of home central to control and automate the lighting, the bulbs can actually behave quite cleverly - as long as you create a system that gives them that ability.In recent years, LED lighting has fallen sharply in price, and this also applies to the smarter alternatives.Giving your home a touch of "smartness" has never been as easy and affordable as it is today.To be smart, the light bulbs must be able to communicate.With today's smart lighting, three different wireless network technologies are typically used: Wi-Fi, Bluetooth and ZigBee.These are probably familiar to several of our readers, but we will take a quick review anyway:Wi-Fi is the standard so to speak that everyone has at home, i.e. the wireless home network that gives us internet and contact with other computers and mobile gadgets.Wi-Fi is widespread, provides a decent range and is fast enough to be able to transfer large amounts of data without having to wait too long.The problem with Wi-Fi is that it requires a relatively large amount of power to have an active connection, but there is no major problem with lighting – after all, the bulbs are connected directly to the mains.Ikea's Trådfri system uses ZigBee.You can think of ZigBee as a kind of particularly low-power variant of Wi-Fi.Both standards operate on the same frequency, but they are very different and cannot "talk to each other".ZigBee has both poorer range and speed than Wi-Fi, but uses so little power that, for example, it makes Philips Hue's motion sensor keep cooking for a couple of years on two AAA batteries.The limited range of typically between 10 and 20 metres, the ZigBee standard solves in a way by creating a mesh network (mesh) with other ZigBee devices.Should you have problems with the range, the solution may be to insert another smart light bulb.The downside to ZigBee bulbs is that most people don't have hardware that can communicate with them directly.Then a smart hub or a home center that knows the "language" must be purchased.Fortunately, one does not have to cost the world.As is well known, Bluetooth Low Energy (LE) cannot communicate with Wi-Fi or ZigBee either.This power-hungry standard came with Bluetooth 4.0 and allows somewhat decent speeds, but has a relatively poor range and can have problems connecting to many devices.At the same time, certain Bluetooth LE devices can also form mesh networks, although this is not particularly common.Unlike ZigBee, Bluetooth is relatively well-established in most homes.Here, in most cases, you will be able to control the bulbs directly via an app, or automate the whole thing with, for example, Apple HomeKit.Products from the same manufacturer tend to stick to one wireless technology, but there is also some lighting that can communicate in several ways.Other manufacturers have equipped almost identical products with different wireless technology intended for different markets.No matter what kind of technology is used to communicate with the smart bulbs, you usually have some choices when it comes to controlling the lighting.App for iOS for Philips Hue.Via own app: Most people who push a smart light bulb onto the market also come with an app that allows you to use your mobile phone or tablet to control the bulb.This is particularly easy with lighting that communicates via Wi-Fi or Bluetooth.The disadvantage of this type of control is that, even if the light can be controlled remotely, it does not feel particularly smart to have to open three different apps to switch off the lights from three different manufacturers.Via third-party app: Some smart lighting can be used together with competitors' or partners' software and possibly hardware.This makes it possible to stick to one system or app, while giving you a little more freedom in terms of selection and price ranges.Via home center via connected service: Relatively inexpensive home centers such as Google Home can be connected to a great many smart gadgets - including lights.You'll often still have to create an account and set up your lights with the manufacturer's original app, but after linking that account to the Google Home app, you can get away with only bothering with the latter.That way, you get voice control in one fell swoop.Via home center directly: Some home centers are able to communicate with a lot of smart lighting directly, and then you avoid the trouble of setting up a new account for each smart bulb manufacturer you have taken into your home.Nevertheless, it can occasionally be worth linking the lighting to the original app.Firstly, this may be the only way to get firmware updates, so make sure the lighting is up to date.The second is that the original app can open up functionality that is not possible in a third-party app.Also note that one does not normally exclude the other.You can just fine use a home center for daily control and automation, and only fire up the original app when you want the lights to do something very special.PS: We are planning a large collective test of smart light bulbs in the near future, so stay tuned!Responsible editor: Gard Steiro