Yo.

A while back Mum bought a table lamp that was 'touch dimming' where
repeated 'touches' to the lamp body gave you from off to 'low', 'med',
full and off again. I think it suggested a 'max' 40W (ses,
incandescent) mini globe but I think I tried a 30W equiv LED and it
appeared to works fine.

She has now got a couple more such lamps beside a bed and so I bought
a couple more LED lamps but this time I went for 40W equiv units, not
considering the tops weren't 'frosted' like the first one. Now, they
work ok but because you are often standing over those lights when you
turn them on ... and these particular lamps go 'off / full / med / dim
/ off', you get a face full of fairly bright light. ;-(

Now, whilst it's no biggie, I checked back in Homebase and it seems
most of the (TCP) ses LED mini globe LEDs that are dimmable are the
same (clear tops) but there are frosted top lamps but they are marked
as 'non dimmable'.

So, assuming the first LED lamp I tried was also non-dimmable and
seems to work fine, what is it about 'dimmable' that makes them so
please. Would there be any issues using non-dimmable LEDs with a
dimmer like that if they actually seem to work ok or could it cause
the lamp to fail prematurely or worse?

Cheers, T i m.

On Monday, 4 April 2016 17:29:50 UTC+1, T i m wrote:

So, assuming the first LED lamp I tried was also non-dimmable and
seems to work fine, what is it about 'dimmable' that makes them so

RC power supply

please. Would there be any issues using non-dimmable LEDs with a
dimmer like that if they actually seem to work ok or could it cause
the lamp to fail prematurely or worse?

immediate failure or fire due to severe overheating of the power supply resistor.


NT

On Mon, 4 Apr 2016 11:48:00 -0700 (PDT), wrote:

On Monday, 4 April 2016 17:29:50 UTC+1, T i m wrote:

So, assuming the first LED lamp I tried was also non-dimmable and
seems to work fine, what is it about 'dimmable' that makes them so

RC power supply

Ok.

please. Would there be any issues using non-dimmable LEDs with a
dimmer like that if they actually seem to work ok or could it cause
the lamp to fail prematurely or worse?

immediate failure

Well, it seems to have been fine so far so it either was a dimmable
lamp in the first place, Mum has only been using it on full (not
unlikely) or we have been lucky?

or fire due to severe overheating of the power supply resistor.

Well I'd *hope* it wouldn't catch fire under any circumstances (even
misuse) but just 'fail to work any more' but I will be checking to see
if I can confirm if it is dimmable or not (it has the TCP markings
that might tell me) and not use it in that lamp if it isn't or we
can't be sure.

Our bedside light failed recently (40W ses candle) and I replaced that
with a dimmable LED candle.

Thanks for the feedback.

Cheers, T i m

I'd not expect there to be any problems, but it really does depend on
several things you probably cannot know from looking at the lamp or led.
For a start, the led may be a pretty crappy switch mode supply and may not
take that kindly to the weird waveform being fed to it by the
dimmer.,Whether it will cause a failure is hard to say. Personally I'd doubt
it but at some brightness's the system may hunt up and down or just refuse
to light without it being full on first.
There could be inductive components in the led that could but probably
won't blow up the dimmer.
I'd be tempted to try it with some well known leds and see what you get.
You cannot know how sophisticated or otherwise the dimmer in the lamp is of
course.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
wrote in message
...
On Monday, 4 April 2016 17:29:50 UTC+1, T i m wrote:

So, assuming the first LED lamp I tried was also non-dimmable and
seems to work fine, what is it about 'dimmable' that makes them so

RC power supply

please. Would there be any issues using non-dimmable LEDs with a
dimmer like that if they actually seem to work ok or could it cause
the lamp to fail prematurely or worse?

immediate failure or fire due to severe overheating of the power supply
resistor.


NT

No I'd not expect any resistors in modern leds, as the current limiting is
doone in the power supply, which is why some hunt up and down when given odd
waveforms. The same issue can happen if you run leds off some older
invertors. Mind you as has been said, if it did go, it would not I think be
likely to catch fire.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"T i m" wrote in message
news
On Mon, 4 Apr 2016 11:48:00 -0700 (PDT), wrote:

On Monday, 4 April 2016 17:29:50 UTC+1, T i m wrote:

So, assuming the first LED lamp I tried was also non-dimmable and
seems to work fine, what is it about 'dimmable' that makes them so

RC power supply

Ok.

please. Would there be any issues using non-dimmable LEDs with a
dimmer like that if they actually seem to work ok or could it cause
the lamp to fail prematurely or worse?

immediate failure

Well, it seems to have been fine so far so it either was a dimmable
lamp in the first place, Mum has only been using it on full (not
unlikely) or we have been lucky?

or fire due to severe overheating of the power supply resistor.

Well I'd *hope* it wouldn't catch fire under any circumstances (even
misuse) but just 'fail to work any more' but I will be checking to see
if I can confirm if it is dimmable or not (it has the TCP markings
that might tell me) and not use it in that lamp if it isn't or we
can't be sure.

Our bedside light failed recently (40W ses candle) and I replaced that
with a dimmable LED candle.

Thanks for the feedback.

Cheers, T i m

On Tue, 5 Apr 2016 08:58:15 +0100, "Brian Gaff"
wrote:

snip good reply

I'd be tempted to try it with some well known leds and see what you get.

For what it's worth Brian I think Mum has had that potentially
non-dimmable LED in there for some time now and there is no sign (that
I have noticed) of any flickering, unexpected brightness changes or
lack of response from the fitting with controlling the thing in
general. As mentioned elsewhere, it *could* be a dimmable LED in there
already but my question was initially 'what if it isn't'.

You cannot know how sophisticated or otherwise the dimmer in the lamp is of
course.

Agreed ... that said, I wasn't really sure how well a 'low energy'
lamp would respond (lumens wise) in a fitting possibly designed for an
incandescent but it works perfectly with a good range of light levels
per touch on the lamp.

FWIW, I think there were fairly expensive LEDs, eight quid or but not
that that would guarantee to tell us anything but it might suggest
they had used better electronics than a cheaper model?

On that particular fitting / LED I'll see if I can cross reference the
numbers and see if it was an actual dimmable model but if there even
could be issues using a non-dimmable in a dimmer, I'll try to avoid
it. I was thinking there must be a good reason why most LED lamps
aren't dimmable but I was just wondering 'why'.

Cheers, T i m

On Tuesday, 5 April 2016 08:58:19 UTC+1, Brian Gaff wrote:
tabbypurr wrote in message
...
On Monday, 4 April 2016 17:29:50 UTC+1, T i m wrote:

So, assuming the first LED lamp I tried was also non-dimmable and
seems to work fine, what is it about 'dimmable' that makes them so

RC power supply

please. Would there be any issues using non-dimmable LEDs with a
dimmer like that if they actually seem to work ok or could it cause
the lamp to fail prematurely or worse?

immediate failure or fire due to severe overheating of the power supply
resistor.

I'd not expect there to be any problems, but it really does depend on
several things you probably cannot know from looking at the lamp or led.
For a start, the led may be a pretty crappy switch mode supply and may not
take that kindly to the weird waveform being fed to it by the
dimmer.,Whether it will cause a failure is hard to say. Personally I'd doubt
it but at some brightness's the system may hunt up and down or just refuse
to light without it being full on first.
There could be inductive components in the led that could but probably
won't blow up the dimmer.
I'd be tempted to try it with some well known leds and see what you get.
You cannot know how sophisticated or otherwise the dimmer in the lamp is of
course.
Brian

not one single point correct of course

On 04/04/2016 19:48, wrote:
On Monday, 4 April 2016 17:29:50 UTC+1, T i m wrote:

So, assuming the first LED lamp I tried was also non-dimmable and
seems to work fine, what is it about 'dimmable' that makes them so

RC power supply

please. Would there be any issues using non-dimmable LEDs with a
dimmer like that if they actually seem to work ok or could it cause
the lamp to fail prematurely or worse?

immediate failure or fire due to severe overheating of the power supply resistor.


NT

Just for info...

I took one apart - it was 4.5W golfball (30W equivalent) and supposedly
not specifically dimmable, but I guess it would.

There was a series input capacitor feeding a full wave bridge with an
electrolytic reservoir capacitor on the DC side, then 50 ohms to a
series string of 14 white LEDs on a separate PCB. Plus other high value
resistors as bleeders.

The LED PCB was well gunked onto an aluminium heatsink with thermal
grease. Simple but it worked.

Cheers
--
Syd

On 05/04/16 10:40, Syd Rumpo wrote:
On 04/04/2016 19:48, wrote:
On Monday, 4 April 2016 17:29:50 UTC+1, T i m wrote:

So, assuming the first LED lamp I tried was also non-dimmable and
seems to work fine, what is it about 'dimmable' that makes them so

RC power supply

please. Would there be any issues using non-dimmable LEDs with a
dimmer like that if they actually seem to work ok or could it cause
the lamp to fail prematurely or worse?

immediate failure or fire due to severe overheating of the power
supply resistor.


NT

Just for info...

I took one apart - it was 4.5W golfball (30W equivalent) and supposedly
not specifically dimmable, but I guess it would.

There was a series input capacitor feeding a full wave bridge with an
electrolytic reservoir capacitor on the DC side, then 50 ohms to a
series string of 14 white LEDs on a separate PCB. Plus other high value
resistors as bleeders.

The LED PCB was well gunked onto an aluminium heatsink with thermal
grease. Simple but it worked.


And I think that is the key to why LED bulbs are pretty good. The
circuitry is much simpler than the CFLs.

And, sticking what amounts to a capacitative load on the mains is going
to make the Grid happy, to offset all those inductive loads in motrs etc.

But because its a capacitative load, don't except dimmers to behave as
expected.


Cheers


--
You can get much farther with a kind word and a gun than you can with a
kind word alone.

Al Capone

On 05/04/2016 10:40, Syd Rumpo wrote:


I took one apart - it was 4.5W golfball (30W equivalent) and supposedly
not specifically dimmable, but I guess it would.

snip

http://www.google.com/patents/US20070025109

Similar, except his diodes are of the dark emitting variety.

Good old US patent office, still at least it's only an application, not
a grant.

Cheers
--
Syd

On Tuesday, April 5, 2016 at 12:48:22 PM UTC+1, Syd Rumpo wrote:
On 05/04/2016 10:40, Syd Rumpo wrote:


I took one apart - it was 4.5W golfball (30W equivalent) and supposedly
not specifically dimmable, but I guess it would.

snip

http://www.google.com/patents/US20070025109

Similar, except his diodes are of the dark emitting variety.

Good old US patent office, still at least it's only an application, not
a grant.

Cheers
--
Syd

Sure they got a grant on something similar, LED Patents, mumble, grumble...etc.

But it is how a lot of the 5050 based lamps are built

http://www.bigclive.com/ledlmp.htm

On Tue, 05 Apr 2016 10:06:34 +0100, T i m wrote:

On Tue, 5 Apr 2016 08:58:15 +0100, "Brian Gaff"
wrote:

snip good reply

I'd be tempted to try it with some well known leds and see what you
get.

For what it's worth Brian I think Mum has had that potentially
non-dimmable LED in there for some time now and there is no sign (that I
have noticed) of any flickering, unexpected brightness changes or lack
of response from the fitting with controlling the thing in general. As
mentioned elsewhere, it *could* be a dimmable LED in there already but
my question was initially 'what if it isn't'.

You cannot know how sophisticated or otherwise the dimmer in the lamp
is of
course.

Agreed ... that said, I wasn't really sure how well a 'low energy' lamp
would respond (lumens wise) in a fitting possibly designed for an
incandescent but it works perfectly with a good range of light levels
per touch on the lamp.

FWIW, I think there were fairly expensive LEDs, eight quid or but not
that that would guarantee to tell us anything but it might suggest they
had used better electronics than a cheaper model?

On that particular fitting / LED I'll see if I can cross reference the
numbers and see if it was an actual dimmable model but if there even
could be issues using a non-dimmable in a dimmer, I'll try to avoid it.
I was thinking there must be a good reason why most LED lamps aren't
dimmable but I was just wondering 'why'.


Well, it's common practice with the lower wattage LEDs (sub 10 watts,
possibly even higher) to use a 'lossless' capacitive dropper in series
with an inrush current limiting resistor which is designed to cope with
low duty cycle switch on events as well as to typically perform as a
safety fuse - it adds a small loss in efficiency but is an essential
component in such a 'Lossless Dropper' circuit.

Conventional triac based dimmer switches use phase delay control over
triggering the triac into conduction so that at the dimmest setting, only
the tail end of each half cycle of mains is applied to the lamp (at a
hundred times per second on 50Hz mains) which reduces the average voltage
supplied to the lamp.

This works just fine with incandescent lamps but results in rather
brutal current switching transients in devices using the 'Lossless
Dropper' power supply circuit (a hundred such events per second rather
than the maximum of two or three per second that a determined on/off
switching freak might apply to the light switch in an attempt to break a
new 'personal best' record.

The worst case condition being the notional half brightness setting
where the triac turns on at the peak voltage in each half cycle to
present the trailing half of the mains waveform to reduce the average
voltage to half. I should imagine that most such LED lamps using the
lossless dropper technique will succumb rather swiftly at this setting of
the dimmer by causing the inrush current limiting/stroke safety fuse
resistor to overheat and let out its magic smoke.

If it's a cheap poundland lamp and you wanted to test whether it would
deal with such a dimmer, using the half brightness setting to run the
test should provide the answer in the shortest time possible. You'll need
to vary the setting either side of the perceived half brightness point if
it doesn't fail straight away since there's rarely a direct relationship
between light output and dimmer setting even with the incandescent lamp
types the dimmer was designed to control (in part because the response of
human vision approximates to a logarithmic one and also because of the
reduced efficacy of a filament lamp at lower average power levels - non-
dimmable LEDs can behave unpredictably unless you know and can analyse
the circuitry used by the lamp).

--
Johnny B Good

On Tue, 05 Apr 2016 10:47:57 +0100, The Natural Philosopher wrote:

====snip====

And, sticking what amounts to a capacitative load on the mains is going
to make the Grid happy, to offset all those inductive loads in motors
etc.

If enough of this type of lamp comes into common use in households
nationwide, the national grid may become rather *unhappy* at such a
destabilising level of leading current appearing in the grid.

It's not just cheap emergency gensets that suffer uncontrolled voltage
regulation due to a 3 or 4 mF capacitor being placed across their 230v
2.8KVA output which, in the case of a 4.7mF load sent such a genset's
output voltage north of the 270 volt mark.

The PSUs (Public Supply Utilties) only require that such industrial
inductive motor loads be corrected to a lagging PF of 90% which suits
both the PSU and its industrial customers since the cost of such PFC
equipment would be doubled if they required these customers to fully
correct to a unity PF.

--
Johnny B Good