Incandescent bulbs - decision, plus Edison Screw question

"tim....." wrote in message
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"Roderick Stewart" wrote in message
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On Tue, 27 May 2014 17:53:27 GMT, Paul Ratcliffe
wrote:

Yes, but...

savings vary with the type of bulb, but for example a Homebase 6W LED
bulb claims to be equivalent to a 37W incandescent, and a 12W LED
equivalent to a 60W, and from my own observation that looks about
right

...I don't have any 40W or 60W bulbs. What can I get to replace
100W or even 150W incandescents?

Light fittings that take more than one bulb. Even if you were staying
with incandescents, why would you want to concentrate all that heat in
one socket anyway? It just makes the plastic brittle.

what plastic?

The bakelite moulded round the brass receptacle with the bayonet slots in
it - when that crumbles the metal bit is too bendy.

Indy Jess John wrote:

I have one of those on the landing (I am waiting for it to conk out
before I replace it). Its twin which was bought at the same time and
used in another room gave up the ghost when the starter lamp failed.

I think you might be waiting a long time. I had one in an outside lamp
and it lasted right until I moved house and said a grateful goodbye to
the bloody thing. I suspect it will outlive the Earth.

IJJ: I put it to you that life is too short to put up with a dim,
flickery jam jar CFL. Sometimes you gotta take the plunge and throw
something away before it's knackered, even though it goes against the
grain.

--
SteveT

Paul Ratcliffe wrote:

...I don't have any 40W or 60W bulbs. What can I get to replace
100W or even 150W incandescents?

I don't think you can. But I prefer several smaller light sources than
one bloody great big one in the middle of the room, so the problem is a
non-problem for me.

Have you considered using a light fitting with more than one bulb?

--
SteveT

On 27/05/2014 13:57, Max Demian wrote:
I wonder how diabetics manage if they go hyper in the pub?

I suspect you mean hypo.

Reach for the glucose tablets. And they will have them on them if they
have any sense.

Andy

Richard Tobin wrote:

AIUI a big problems with LEDs is that their remarkable efficiency only
applies at low temperatures. From the discussion here they seem to be
able to produce 60W equivalent devices that are more efficient than
CFLs, but not yet 100W equivalents which would get hotter. This will
presumably improve over the next few years.

Hmmm.... are you implying that they get less efficient at higher
temperatures?

I'm not sure about that. I think in reality the reason they don't
exceed 800-odd lumens right now is that it's already bloody difficult
to get the heat away fast enough from such a tiny point source. If you
want air cooling and the same shape/size as a normal bulb, then the
heatsinking they have currently got can't keep an LED chip bigger than
800 lumens cool enough.

I'm sure in due course they'll develop more efficient LED chips which
get less hot for a given light output, and they may well improve
further the heatsinking technology. Then we might get a
100W-equivalent.

Personally I don't ca I'm more than happy enough to use 1 bulb in a
room.

--
SteveT

Bill Wright wrote:

Yes, there's about a hundred of them in parallel. Is that a bad thing?

Weeeelll..... it is if you read the electronics mags. The story goes
that the forward voltage drop varies slightly between otherwise
identical LEDs, and the ones with the lowest forward voltage drop will
hog a disproportionate amount of current, and thus overheat and burn
out.

Does anyone know about the temperature coefficient of LEDs? Does the
forward voltage drop get less or more as they get hotter.

If the former, then you would have the potential for the hottest one to
draw even more current, getting ever hotter in a classical thermal
runaway.

The official story with LEDs is that you should run them in series, so
that they all get the same current whether they like it or not.

As for me, I'm not saying the official story is correct, just reporting
it. You seem to have done perfectly well with them in parallel.

By the way, Bill, how did you get that plate made with the number cut
out? It looks very smart and precisely cut.

--
SteveT

Roderick Stewart wrote:

There are indeed, but beware the "killer corn cob" type that doesn't
have a transparent cover, leaving the strips of circuit board with
their surface mounted LEDs and blobs of solder completely exposed. I'm
amazed it's legal to sell these at all. Perhaps it isn't?

Yes, isn't it astonishing! I couldn't believe it when I saw them for
sale.

--
SteveT

"Roderick Stewart" wrote in message
...
On Tue, 27 May 2014 17:57:34 +0100, "Ian Field"
wrote:

The big snag for us with LEDs was no light behind it. This meant that
when
used from a ceiling light the ceiling was in relative darkness. It seems
that for a comfortable even light we need the dispersion of reflected
light coming off the ceiling.

So I'm told - the cure for this is; "corn cob" style LED replacements.

As yet I've only seen this style as H4 replacements and advertised in an
Indian electronics magazine.

Apparently, there's plenty on Ebay.

There are indeed, but beware the "killer corn cob" type that doesn't
have a transparent cover, leaving the strips of circuit board with
their surface mounted LEDs and blobs of solder completely exposed. I'm
amazed it's legal to sell these at all. Perhaps it isn't?


Out of reach - out of mind.

In article ,
Roderick Stewart wrote:

... and advertised in an
Indian electronics magazine.
^^^^^^^^^^^^^^^^^^^^^^^^^^^

There are indeed, but beware the "killer corn cob" type that doesn't
have a transparent cover, leaving the strips of circuit board with
their surface mounted LEDs and blobs of solder completely exposed. I'm
amazed it's legal to sell these at all. Perhaps it isn't?

Bearing in mind some of the dangerous direct-connected mains
crap posted on sites e.g. instructables.com, notably from Indian
posters, it appears that anything goes when it comes to safety there.

Maybe in India it is *mandatory* for mains connected devices to
be lethal. All I know is that comments pointing out the danger/hazards
are shouted down with "I've done it this way for years and not died, it
is fine" and "You theoreticians worry too much".

Fuses? Optional. Insulation? Sticky tape, blu-tak, whatever you
have. Voltage ratings on capacitors? Made up by idiots, just ignore
them. PCB? No, just bird-nest it.

You get the idea.

I'm fairly sure that on import to Europe/USA someone should notice
bulbs that have live stuff hanging on the outside.
--
--------------------------------------+------------------------------------
Mike Brown: mjb[-at-]signal11.org.uk | http://www.signal11.org.uk

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"Steve Thackery" wrote in message
...
Bill Wright wrote:

Yes, there's about a hundred of them in parallel. Is that a bad thing?

Weeeelll..... it is if you read the electronics mags. The story goes
that the forward voltage drop varies slightly between otherwise
identical LEDs, and the ones with the lowest forward voltage drop will
hog a disproportionate amount of current, and thus overheat and burn
out.

Does anyone know about the temperature coefficient of LEDs? Does the
forward voltage drop get less or more as they get hotter.

Vf decreases with rising temperature, so the one with lowest Vf to start
with draws more current and gets hot, then its Vf drops even lower making it
get even hotter.

Its called thermal runaway.

A transistor would fail short circuit and most likely short the supply to
all the others, but the bond wires on LEDs are thin as they can get away
with so it doesn't obstruct much light, so when the LED fails short circuit,
the bond wire will probably break leaving all the more current to share out
and take out the LED with the next lowest VF.

Sometimes when the bond wire breaks, it becomes temperature intermittent -
so the LED flashes as it heats and cools.

Those 24 LED headband lamps and 72 LED worklights are usually parallel - -
they usually show it by first one LED fails - then in increasing numbers.