Why do LEDs generate heat?

[Tim Streater]

IR: also known as 'heat'.

[Commander Kinsey]

Surely not required for the plants, as the room is heated by a greenhouse heater. Or do they insist on absorbing some through radiant energy?

[Tim Streater]

Go stand in the Sun and see if you absorb heat through radiant energy.

[Commander Kinsey]

I do, but I don't need it. We can be in a warm room and be comfortable without any radiant heat. Are plants not the same?

[Robert]

Besides the inefficiencies in the LED itself which other posters have covered, LED lamps have some current regulation or power supply built-in which will not be 100% efficient and thus generates heat.

[Commander Kinsey]

True, but it's the LEDs themselves that are the warmest, and also the most susceptible to heat.

[NY]

But if you feel a Philips Hue bulb which is the size of an old tungsten 100W bulb, the part that gives off light (presumably where the LEDs are) is cool. It is the neck, near the fitting, which gets hot - and I presume that's where the PSU is.

Likewise for GU10 bulbs (Philips Hue or ordinary non-dimmable LED) the front and conical sides don't get hot, whereas the neck near the fitting gets hot.

[Commander Kinsey]

Or where the heatsink from the LEDs is.

[PeterC]

If my meter is correct, all the LEDs that I've measured have a PF of approx.

0.5 - not a good start. One TV has a PF of 0.97 and is barely warm over the PSU; another is 0.86 and is luke warm. The real warmth in the 2nd. one is around the inputs though - SPDIF, USB and HDMI.

[Clive Arthur]

<snip>

They make something which looks white for many or maybe most purposes, but they don't make white. They don't make anything above blue, so no violet, and nothing below 'normal' red, so no deep red, and there are significant gaps between the colours.

Cheers

[whisky-dave]

I doubt you're the only one wanting that. When they become avaible you be able to buy them, but for now it seems the more effiecient something is the more it costs, so don't expect them to be on ebay 100 for £1 or whatever.

[Commander Kinsey]

Is power factor that important? In a domestic building, you are not billed for power factor. I might have a capacitive load, but my neighbour has an inductive load, so they even out. You don't get extra heat generated from a low power factor.

[Commander Kinsey]

Well huge strides have been made already, so I guess more will happen later on.

[whisky-dave]

Don't forget the 4 colour ones we are using.

RGB+W although you can generate while light from red, blue & green it is better to have a dedicated white LED in the package.

true handy for growing peppers or so I've heard.

[Commander Kinsey]

I found them good for recovering damaged plants my cats have broken, like spider plants which they love to sit on. They're also allegedly good for marijuana :-)

[Commander Kinsey]

I just tested one of mine with a meter, and it gave a power factor of 1.00, at 256V, 9.8W. Yes I know that's an absurdly high voltage, but I live opposite the substation so it's higher than the rest of the street, and they won't do anything about it. I consequently run my computer, lights, etc off a UPS, which automatically chops 10 or 20V off when needed. It's the cool white, 9W version of this (not necessarily from this seller, but they look identical):

contain a pretty decent looking switched mode PSU, unlike some other bulbs I've seen which have a very simple capacitor dropper. If any health and softy people want to be annoyed, then be aware that I don't earth them. A couple of them made a humming noise when I did. If I touch the metal casing of an unearthed unit, and rub my finger along it, I feel a slight vibration. I guess something is jumping across by induction.

[whisky-dave]

Not that I have heard they just don't have the intensity or the longer blue wavelenghs.

[whisky-dave]

I doubt that it's just the LED, you shouldn't include the PSU in such calculations especailly if running off mains AC, because you're including the LED+PSU so not really gettign any info about the actual LED.

[Commander Kinsey]

Well I can confirm they resurrected several damaged houseplants (including spider plants and cactuses), which grew faster than they would have done on a windowledge, and plenty websites recommend them for marijuana growth.

[Commander Kinsey]

Why should I not include the whole unit? Surely that's all that matters.