LED lamps revisited

[Mike Tomlinson]

I've been following the various discussions about how LED low-energy lamps are steadily improving. Bought a couple of GU10 replacements from B&Q recently and was very disappointed - a cold blueish light with a poor colour spectrum.

I recently grabbed one of these from fleabay:

's a 108 LED low-energy lamp. Came from Hong Kong in about a week. Worth a look for $1. Described a 'corn bulb' which works, it feels just like holding a cob of corn.

Counted the LEDs - yes, 108. Smaller than it looks in the pics. The 'bulb' is octagonal, presumably to evenly distribute the direct light emitted by the LEDs. There are 12 LEDs on the end to provide downward as well as sideways light.

Seems well made, though I haven't opened it. Not expecting wonders, some of these Chinese-made things are real horrors. There is a dodgy- looking CE sticker (I don't believe for one second that it's been tested) and no other markings or approval/safety stickers. Doubt I would use those unattended in the house until quality branded and safety tested ones come on the market, but would be OK with it in an enclosed outdoor fitting where it wouldn't do any damage if it decided to self- combust.

Draws 25mA at 240V, so about 6.5W as opposed to the claimed 5W at

200-220V. The ebay ad doesn't make a claim for incandescent equivalent, but after testing it I'd guess at 40W.

The light is a very cold white with a slight blue tinge, but not as bad as some I have seen. The LEDs are uncomfortably bright to look at directly. Don't have much of a feel for colour spectrum yet but don't think it is good.

I wouldn't use these where they could be seen by the naked eye, but could see them working well in shades, particularly frosted glass shades which would diffuse the light.

On a related topic, CFLs are also improving. Bought half a dozen 7W twisted-candle CFLs from Tesco for 20p each recently and they are excellent. These are the first CFLs I've used that I would be happy to fit around the house. I've lightly sprayed a couple with red enamel paint to replace fireglow bulbs and they look good.

That said, I don't think CFLs are a universal panacea. There are occasions when you just want the warm glow of an incandescent. My contribution to energy saving is to turn lights off when I don't need them. Simple, eh? :)

[Matty F]

> it's a 108 LED low-energy lamp. Came from Hong Kong in about a week.

I've had around 50 LEDs running outside in my imitation gaslamp for a couple of years.They seem very reliable and don't give out much heat. At the rate the price is dropping I hereby predict that LEDs will take over from all other lights in the next few years. In NZ we are using them for traffic lights, and most new cars seem to use them for tail lights and sidelights. I don't see why there isn't a mixture of different coloured LEDs in the cluster, if people are really worried about a cold white light. Which I am not. Low power usage and long life are the most inportant factors to me.

[Man at B&Q]

The device from Ebay looks like it is just a load of 5mm white LEDs, a completely different beast to LEDs designed for incandescent replacement. The latter *do* give out a lot of heat when driven hard enough to be effective as lighting.

MBQ

[Dave Plowman (News)]

It's possible today to make a fluorescent tube with pretty well any colour temperature you want. And you can get them for ordinary fittings, although only from a specialist. CFLs tend to be built down to a price.

LEDs are a long way from this - and IMHO will never achieve it. As the efficiency goes down with each attempt.

[Andrew Gabriel]

I think that prediction has been continuous for last 20 years, and so far, 100% wrong. The reasons it's been wrong for last 20 years haven't gone away. What is perhaps changing is the realisation that these issues probably aren't going to get fixed (e.g. making an LED which will work efficiently at 200C, or even at all, which can replace existing lamps) and different solutions are required.

They certainly have niches where they're ideal - single colour directional lighting being top of the list.

1) Patents. In the lighting industry outside of LEDs, cross licensing of patents has been pretty universal for almost 100 years. LED lighting is coming from different players, and they just don't do it. This means you have to wait 25 years for patents to expire before technology becomes widespread enough to drop to consumer level pricing. 2) Separation of colour light sources generates quite difficult design challenges. Firstly, you get an effect which looks like chromatic aberration on steroids. Also you have to mix evenly in all directions or the colour changes by angle. Neither are easy to solve efficiently.

[John Rumm]

You can't really predict the actual power consumed on these just from a voltage and current measurement. So there is a fair chance it is 5W or even less...

200-220V. The ebay ad doesn't make a claim for incandescent equivalent,

I have seen some LED lights where the light quality is as good as a CFL, which admittedly is not saying much, but sounds better than this example.

[Gareth]

LEDs have a huge efficiency advantage where you want coloured light; they produce the colour you actually want rather than producing white and filtering it. The increased reliability will reduce maintenance costs significantly for things like traffic lights.

I still like the light from conventional bulbs and I find the time it takes CFLs to warm up really annoying. I recently bought some halogen bulb replacements for ordinary light bulbs. Though not as efficient as CFLs or LEDs these claim to be more efficient than ordinary filament lamps, give a nice light, come on instantly and work with dimmer switches. To me these seem like a good compromise, especially as they were 10p each in the "reduced to clear" bin.

[Mike Tomlinson]

In article , Man at B&Q writes

Pretty sure they are, yes.

[Mike Tomlinson]

In article , John Rumm writes

indicates power factor, so will bung the lamp on that and report back.

Well, it was only $1. worth it for a play.

I can remember when LEDs were $1/£1 *each*

[Man at B&Q]

Except when you actually want white.

Or you need a wavelenght that cannot be produced using any of the materials used to make LEDs. For some time it was simply not possible to replace the warning lights at level crossings with LEDs, as they simply couldn't produce the colour that was laid down in regulations. That may have changed now.

MBQ

[Man at B&Q]

You're not that old if they were only $1/=A31!

MBQ

[John Rumm]

Well I only remember as far back as when the choice was limited to red, amber, and green!

[Andrew Gabriel]

interactive toys to play with this at: will either be simple capacitive dropper (which is example 1), or switched mode PSU (which is example 3).