On Fri, 04 Oct 2019 23:49:23 +0100, AlexK wrote:



"Commander Kinsey" wrote in message
news
On Fri, 04 Oct 2019 19:56:29 +0100, AlexK wrote:



"Commander Kinsey" wrote in message
news On Fri, 04 Oct 2019 09:41:25 +0100, PeterC

wrote:

On Thu, 3 Oct 2019 19:29:42 +0100, Robert wrote:

On 03/10/2019 14:29, Commander Kinsey wrote:
Why do LEDs generate heat? I want a technical answer not "because
they're inefficient". And will we ever make them more efficient?
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.

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.

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): http://www.ebay.co.uk/itm/262915986742
They 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.

More likely the capacitance effect you get with double insulated stuff.

Could be. Would that also cause the buzzing when earthed?

That's more likely to be due to a significant earth current when earthed.
Easy to measure.

0.020mA per foot of lighting (they're 4.5W per foot). I don't call that significant and can't see how it would cause an audible vibration.