In the last few years, it seemed that carbon-filament style globes grew drastically in popularity for mood lighting in many commercial and home settings. Their warm orange glow is distinctive, and nostalgic. While the government in Australia had done a lot to ensure the timely death of incandescent globes, it seemed that this may have been a reversal in an otherwise positive trend.
Many buyers of carbon-filament style lamps may not be aware that, despite their seemingly low 25W rating, they actually have a lower luminous efficacy than even old fashioned regular light globes. As a result, these decorative lamps rarely even state their lumen output – my best estimates put the luminous efficacy at just 6.67lm/W for filament types with a 25W globe only putting out 167 lumens. This compares very poorly to the traditional globe which easily achieves 15lm/W, and LEDs which routinely achieve 100-120lm/W. As a result, when decorative filament globes are used for whole-area lighting, an ecological disaster is on the cards.
To capitalize on this growing market, specialty LED globes have been designed. IKEA’s earlier attempt (Nittio) used a spiral light-pipe to channel warm white light from LEDs mounted in a base to create the visual effect. Initially, it was quite expensive and its limited light output was a limitation.
However, since then, LED-filament style globes have appeared on the market using chip-on-glass and remote-phosphor technology. This allows many smaller discrete LED chips to produce a nearly uniform “line” of light, in a warm glow similar to incandescent globes. Initially confined to Chinese manufacturers, it seems that IKEA have embraced this trend with their Lunnom series.
Visiting my local IKEA, I found that the large E27 version of the globe (LED1637G6/403.765.29/19972) was marked down to AU$9.99, so I decided to give it a shot and see what it was like. Note that there is a smaller E27 version of the globe, which would be preferable for luminaire compatibility reasons, but was out of stock at the time I visited. While I suspect it is similar, I cannot confirm this as I have not tested it.
If you’re in the shop, you definitely won’t miss the Lunnom. It comes packaged in a clear plastic box, showing off the globe’s design in its entirety. In traditional IKEA minimalism, the minimal amount of text is placed on each panel. This particular Lunnom is a 5.5W model offering a 600lm output, which is roughly the same as a 40W incandescent globe. Other specifications include a power-on time of <1 second, 15,000 switching cycles, 220-240v 50/60Hz supply compatibility, >80 CRI and 109lm/W luminous efficacy. Even compared with non-decorative LED globes, its luminous efficacy is impressive.
Other key specifications include a 2200K CRI, making it a very warm white. It is not compatible with dimmers. It claims a 15,000h lifetime, which is about five times longer than traditional filament decorative globes which top-out at 3,000h. Its dimensions are 175mm length and 125mm diameter with an E27 base, making this a large globe that is not compatible with many luminaires. It’s probably best used with a pendant. It achieves an A++ EU Energy rating, and is from the Week 27 of 2017 batch. It is marked with the appropriate RCM for Australia. There is a warning not to use the globe if the outer envelope is damaged or broken due to risk of electric shock – this suggests a non-isolated driver may be involved, but also high voltages.
The bulb is made of glass, and is large and bulbous. Unlike filament globes, the glass envelope is (probably) not evacuated, but instead is used for its decorative effect and as electrical insulation from the parts inside. Due to the decorative nature of the design, the driver has been hidden away into a PCB in the end-cap. Four LED filament sections can be seen, supported by a central glass stem.
The globe information is printed on the short neck area, so as not to detract from the aesthetics.
The LED arrangement does not seem obvious at first, but it appears to be two filaments in series by two strings with (possibly) a separate current regulation channel. Note the diagram below is based on the wiring visible through the glass alone, and the actual diode direction (i.e. high side/low side regulation) was not determined.
Powering up the globe revealed a brighter-than-expected warm white glow very much reminiscent of incandescent globes. It was probably not quite as warm as a filament globe, close to that of an incandescent globe, but definitely warmer than my “new” halogen-substitute globe.
Note that both images are corrected to a 6500k white point with no tint. Based on the white balance tool in Lightroom, the IKEA globe was spot-on at 2200K. While the quality of the light was good, the filament-aesthetics were still obviously an emulation. Given the present LED technology, this is probably the best we can achieve.
Running at 230V for 20 minutes from cold, the power was about 5.45W, which is pretty much spot-on. The steps in the graph are due to the power supply regulation (i.e. as the inverter heats up, the duty-cycle steps cause the output voltage to jump 1-2V at a time).
Performing a voltage-sweep on the globe shows that it survived running at 277V. However, it also showed the globe is unlike many LED globes on the market in that its best operating point actually lies within the operating voltage range. Being sensitive to voltage, the globe flickers below 200V. The globe only reaches full brightness around 227V, but then from then on, the brightness remains relatively constant. The increase in power consumption from there may be related to power dissipation in the regulation circuit. As a result, if your mains voltage is a little weak, the globe may not deliver its full rated output – falling to half its output at about 202V. The power factor is also not impressive, ranging from 0.55 to 0.58, suggesting possible corner-cutting to save money. However, it could be a form-factor restriction of fitting the driver in the cap of globe, but it doesn’t really matter as it won’t change a residential household power bill.
Being a little curious about what sort of driver might be used, I decided to try and see if any flicker was detectable. Using an LED as a sensor, the output seemed to be quite stable (for the most part) suggesting a capacitor may be present in the circuit to maintain a flicker-free output. The same LED sensor easily detected the 100Hz flicker in a fluorescent desk lamp, as a cross-check of its sensitivity.
As it turns out, decorative lighting doesn’t have to kill the planet or your wallet. The IKEA Lunnom comes from a trustworthy source, at a price that makes traditional filament versions of the globe uneconomical from purchase price alone based on the lifetime differences. With a very impressive 109lm/W luminous efficacy and a 600lm output which is about 40W-incandescent-equivalent, it’s a very compelling package. When you add up savings in electricity, it seems a no-brainer to opt for LED filament globes over traditional filament globes where a decorative effect is desired. The one thing you might miss is the actual shape of the filament – while this globe does “try” with angular straight sections, a hanging filament does have the subtle curves between supports which such straight-LED-filaments can’t emulate.
While I’m not able to assess the actual lifetime of the globe, nor its driver design, considering its inexpensive nature, I think it’s an easy choice for those looking for this type of lighting. The one thing I would be careful of is the (likely) non-isolated and high voltage nature of the current driver’s output, so I would definitely advise heeding the advice not to contact any parts if the outer glass envelope is broken.
Another downside of this particular globe is the lack of dimmer compatibility – however, there are other products (more expensive) that feature dimming compatibility. Finally, it seems the power factor is fairly low at 0.56, although this doesn’t directly matter for home consumers, it isn’t “utility friendly” and suggests some corners being cut to save on manufacturing cost.