I replaced a load of ceiling lights in the house yesterday with LED
fitments. I noticed that one of them continued to glow for some time
after being turned off. The others don't do this.

I swapped the light out, and the replacement doesn't glow.

Just to treble-check, I wired up the glowing light to a 13 amp plug, and
it still glows after being unplugged.

https://www.tlc-direct.co.uk/Products/GLCPL6CT.html

On Fri, 4 Nov 2022 15:13:38 +0000
GB <NOTsomeone@microsoft.invalid> wrote:

> I replaced a load of ceiling lights in the house yesterday with LED
> fitments. I noticed that one of them continued to glow for some time
> after being turned off. The others don't do this.
>
> I swapped the light out, and the replacement doesn't glow.
>
> Just to treble-check, I wired up the glowing light to a 13 amp plug,
> and it still glows after being unplugged.
>
> https://www.tlc-direct.co.uk/Products/GLCPL6CT.html
>

Sounds like phosphors. LEDs certainly don't glow after removal of the
current. Some 'white' LEDs are actually UV, some are blue, and both use
phosphors to simulate white. Perhaps your odd one used different,
longer-glowing phosphors than the others.

In the days of real oscilloscopes, with some high-end models the
phosphor glow time could be chosen from two or three values.

--
Joe

On 04/11/2022 15:13, GB wrote:
> I replaced a load of ceiling lights in the house yesterday with LED
> fitments. I noticed that one of them continued to glow for some time
> after being turned off. The others don't do this.
>
> I swapped the light out, and the replacement doesn't glow.
>
> Just to treble-check, I wired up the glowing light to a 13 amp plug, and
> it still glows after being unplugged.
>
> https://www.tlc-direct.co.uk/Products/GLCPL6CT.html

It could be that there is supposed to be a resistor in place to
discharge any capacitors in the PSU when it is powered down, and also
reduce the possibility of inductive pickup causing flickering when
turned off. If that were missing or faulty it might not be spotted
during inspection and testing since it would still appear to work
correctly.

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

On 04/11/2022 16:30, John Rumm wrote:
> On 04/11/2022 15:13, GB wrote:
>> I replaced a load of ceiling lights in the house yesterday with LED
>> fitments. I noticed that one of them continued to glow for some time
>> after being turned off. The others don't do this.
>>
>> I swapped the light out, and the replacement doesn't glow.
>>
>> Just to treble-check, I wired up the glowing light to a 13 amp plug,
>> and it still glows after being unplugged.
>>
>> https://www.tlc-direct.co.uk/Products/GLCPL6CT.html
>
> It could be that there is supposed to be a resistor in place to
> discharge any capacitors in the PSU when it is powered down, and also
> reduce the possibility of inductive pickup causing flickering when
> turned off. If that were missing or faulty it might not be spotted
> during inspection and testing since it would still appear to work
> correctly.
>
>

That makes good sense. I'm not intending to open it up at any stage, so
is it worth returning it for that?

On Fri, 4 Nov 2022 16:17:15 +0000, Joe <joe@jretrading.com> wrote:

>On Fri, 4 Nov 2022 15:13:38 +0000
>GB <NOTsomeone@microsoft.invalid> wrote:
>
>> I replaced a load of ceiling lights in the house yesterday with LED
>> fitments. I noticed that one of them continued to glow for some time
>> after being turned off. The others don't do this.
>>
>> I swapped the light out, and the replacement doesn't glow.
>>
>> Just to treble-check, I wired up the glowing light to a 13 amp plug,
>> and it still glows after being unplugged.
>>
>> https://www.tlc-direct.co.uk/Products/GLCPL6CT.html
>>
>
>Sounds like phosphors. LEDs certainly don't glow after removal of the
>current. Some 'white' LEDs are actually UV, some are blue, and both use
>phosphors to simulate white. Perhaps your odd one used different,
>longer-glowing phosphors than the others.
>
>In the days of real oscilloscopes, with some high-end models the
>phosphor glow time could be chosen from two or three values.

Doesn't it depend on the circuitry in the base of the bulb? For
example if there is a capacitor in there that holds charge for a few
moments after the power is turned off, the bulb will continue to glow
until that capacitor loses all its charge through the bulb. Other
circuits may not have such a capacitor and the bulb extinguishes
almost instantly.

--
Chris

On Fri, 04 Nov 2022 16:35:12 +0000
Chris Hogg <me@privacy.net> wrote:

> On Fri, 4 Nov 2022 16:17:15 +0000, Joe <joe@jretrading.com> wrote:
>
> >On Fri, 4 Nov 2022 15:13:38 +0000
> >GB <NOTsomeone@microsoft.invalid> wrote:
> >
> >> I replaced a load of ceiling lights in the house yesterday with
> >> LED fitments. I noticed that one of them continued to glow for
> >> some time after being turned off. The others don't do this.
> >>
> >> I swapped the light out, and the replacement doesn't glow.
> >>
> >> Just to treble-check, I wired up the glowing light to a 13 amp
> >> plug, and it still glows after being unplugged.
> >>
> >> https://www.tlc-direct.co.uk/Products/GLCPL6CT.html
> >>
> >
> >Sounds like phosphors. LEDs certainly don't glow after removal of the
> >current. Some 'white' LEDs are actually UV, some are blue, and both
> >use phosphors to simulate white. Perhaps your odd one used different,
> >longer-glowing phosphors than the others.
> >
> >In the days of real oscilloscopes, with some high-end models the
> >phosphor glow time could be chosen from two or three values.
>
> Doesn't it depend on the circuitry in the base of the bulb? For
> example if there is a capacitor in there that holds charge for a few
> moments after the power is turned off, the bulb will continue to glow
> until that capacitor loses all its charge through the bulb. Other
> circuits may not have such a capacitor and the bulb extinguishes
> almost instantly.
>

Yes, but I wouldn't expect so. The power wasn't mentioned, but I'd
guess around 4-5W. About a third to half an Amp of current, depending
on how many LEDs. That's a hell of a capacitor.

--
Joe

On 04/11/2022 18:07, Joe wrote:
> On Fri, 04 Nov 2022 16:35:12 +0000
> Chris Hogg <me@privacy.net> wrote:
>
>> On Fri, 4 Nov 2022 16:17:15 +0000, Joe <joe@jretrading.com> wrote:
>>
>>> On Fri, 4 Nov 2022 15:13:38 +0000
>>> GB <NOTsomeone@microsoft.invalid> wrote:
>>>
>>>> I replaced a load of ceiling lights in the house yesterday with
>>>> LED fitments. I noticed that one of them continued to glow for
>>>> some time after being turned off. The others don't do this.
>>>>
>>>> I swapped the light out, and the replacement doesn't glow.
>>>>
>>>> Just to treble-check, I wired up the glowing light to a 13 amp
>>>> plug, and it still glows after being unplugged.
>>>>
>>>> https://www.tlc-direct.co.uk/Products/GLCPL6CT.html
>>>>
>>>
>>> Sounds like phosphors. LEDs certainly don't glow after removal of the
>>> current. Some 'white' LEDs are actually UV, some are blue, and both
>>> use phosphors to simulate white. Perhaps your odd one used different,
>>> longer-glowing phosphors than the others.
>>>
>>> In the days of real oscilloscopes, with some high-end models the
>>> phosphor glow time could be chosen from two or three values.
>>
>> Doesn't it depend on the circuitry in the base of the bulb? For
>> example if there is a capacitor in there that holds charge for a few
>> moments after the power is turned off, the bulb will continue to glow
>> until that capacitor loses all its charge through the bulb. Other
>> circuits may not have such a capacitor and the bulb extinguishes
>> almost instantly.
>>
>
> Yes, but I wouldn't expect so. The power wasn't mentioned, but I'd
> guess around 4-5W. About a third to half an Amp of current, depending
> on how many LEDs. That's a hell of a capacitor.

If it is a SMPSU, then the capacitor is usually on the mains side after
a rectifier - so it will be a fraction of a watt at ~330V. So that is
only a few mA

(I certainly have some lamps that glow for a few secs on power off - it
tends to be the more traditional LED ones rather than the "filament"
versions)

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

On 04/11/2022 18:07, Joe wrote:
> On Fri, 04 Nov 2022 16:35:12 +0000
> Chris Hogg <me@privacy.net> wrote:
>
>> On Fri, 4 Nov 2022 16:17:15 +0000, Joe <joe@jretrading.com> wrote:
>>
>>> On Fri, 4 Nov 2022 15:13:38 +0000
>>> GB <NOTsomeone@microsoft.invalid> wrote:
>>>
>>>> I replaced a load of ceiling lights in the house yesterday with
>>>> LED fitments. I noticed that one of them continued to glow for
>>>> some time after being turned off. The others don't do this.
>>>>
>>>> I swapped the light out, and the replacement doesn't glow.
>>>>
>>>> Just to treble-check, I wired up the glowing light to a 13 amp
>>>> plug, and it still glows after being unplugged.
>>>>
>>>> https://www.tlc-direct.co.uk/Products/GLCPL6CT.html
>>>>
>>>
>>> Sounds like phosphors. LEDs certainly don't glow after removal of the
>>> current. Some 'white' LEDs are actually UV, some are blue, and both
>>> use phosphors to simulate white. Perhaps your odd one used different,
>>> longer-glowing phosphors than the others.
>>>
>>> In the days of real oscilloscopes, with some high-end models the
>>> phosphor glow time could be chosen from two or three values.
>>
>> Doesn't it depend on the circuitry in the base of the bulb? For
>> example if there is a capacitor in there that holds charge for a few
>> moments after the power is turned off, the bulb will continue to glow
>> until that capacitor loses all its charge through the bulb. Other
>> circuits may not have such a capacitor and the bulb extinguishes
>> almost instantly.
>>
>
> Yes, but I wouldn't expect so. The power wasn't mentioned, but I'd
> guess around 4-5W. About a third to half an Amp of current, depending
> on how many LEDs. That's a hell of a capacitor.

But the capacitor could be at mains voltage and the circuitry may allow
only a very low current during discharge after switch off.

In article <20221104180758.465ada39@jrenewsid.jretrading.com>,
Joe <joe@jretrading.com> wrote:
> > Doesn't it depend on the circuitry in the base of the bulb? For
> > example if there is a capacitor in there that holds charge for a few
> > moments after the power is turned off, the bulb will continue to glow
> > until that capacitor loses all its charge through the bulb. Other
> > circuits may not have such a capacitor and the bulb extinguishes
> > almost instantly.
> >

> Yes, but I wouldn't expect so. The power wasn't mentioned, but I'd
> guess around 4-5W. About a third to half an Amp of current, depending
> on how many LEDs. That's a hell of a capacitor.

But does it stay at full brightness after the power is turned off? An LED
will stay lit at a very small proportion of the full current, but
obviously not at full level.

--
*If you think nobody cares about you, try missing a couple of payments *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

On Fri, 4 Nov 2022 16:35:09 +0000
GB <NOTsomeone@microsoft.invalid> wrote:

> That makes good sense. I'm not intending to open it up at any stage,
> so is it worth returning it for that?
>
C: "I wish to complain about this light bulb."
S: "Of course, sir. Does it not produce light?"

On 05/11/2022 17:45, Rob Morley wrote:
> On Fri, 4 Nov 2022 16:35:09 +0000
> GB <NOTsomeone@microsoft.invalid> wrote:
>
>> That makes good sense. I'm not intending to open it up at any stage,
>> so is it worth returning it for that?
>>
> C: "I wish to complain about this light bulb."
> S: "Of course, sir. Does it not produce light?"

Reminds me of the trick light bulbs that light up when you hold them in
your hand. "Amaze your friends!" (Until they get so bored with your
silly tricks that they aren't your friends any more.)

--
Max Demian

On 05/11/2022 13:31, Dave Plowman (News) wrote:
> In article <20221104180758.465ada39@jrenewsid.jretrading.com>,
> Joe <joe@jretrading.com> wrote:
>>> Doesn't it depend on the circuitry in the base of the bulb? For
>>> example if there is a capacitor in there that holds charge for a few
>>> moments after the power is turned off, the bulb will continue to glow
>>> until that capacitor loses all its charge through the bulb. Other
>>> circuits may not have such a capacitor and the bulb extinguishes
>>> almost instantly.
>>>
>
>> Yes, but I wouldn't expect so. The power wasn't mentioned, but I'd
>> guess around 4-5W. About a third to half an Amp of current, depending
>> on how many LEDs. That's a hell of a capacitor.
>
> But does it stay at full brightness after the power is turned off? An LED
> will stay lit at a very small proportion of the full current, but
> obviously not at full level.
>

My one is just a faint glow.

On Sun, 6 Nov 2022 19:50:07 +0000
GB <NOTsomeone@microsoft.invalid> wrote:

> On 05/11/2022 13:31, Dave Plowman (News) wrote:

> > But does it stay at full brightness after the power is turned off?
> > An LED will stay lit at a very small proportion of the full
> > current, but obviously not at full level.
> >
>
> My one is just a faint glow.

Like CFLs?

--
Joe

LEDs can easily remain on purely by induced voltages along wires close to
each other. Not much you can do but some of them have a small bleed resistor
inside that makes them discharge anything that might otherwise make them
glow eerily.
Neons in pieces of gear back in the day used to glow purely by the pick up
in the wiring loom, Once again a resistor of around 470k fixed it.
Brian

--

--:
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"GB" <NOTsomeone@microsoft.invalid> wrote in message
news:tk935f$39kgf$2@dont-email.me...
> On 05/11/2022 13:31, Dave Plowman (News) wrote:
>> In article <20221104180758.465ada39@jrenewsid.jretrading.com>,
>> Joe <joe@jretrading.com> wrote:
>>>> Doesn't it depend on the circuitry in the base of the bulb? For
>>>> example if there is a capacitor in there that holds charge for a few
>>>> moments after the power is turned off, the bulb will continue to glow
>>>> until that capacitor loses all its charge through the bulb. Other
>>>> circuits may not have such a capacitor and the bulb extinguishes
>>>> almost instantly.
>>>>
>>
>>> Yes, but I wouldn't expect so. The power wasn't mentioned, but I'd
>>> guess around 4-5W. About a third to half an Amp of current, depending
>>> on how many LEDs. That's a hell of a capacitor.
>>
>> But does it stay at full brightness after the power is turned off? An LED
>> will stay lit at a very small proportion of the full current, but
>> obviously not at full level.
>>
>
> My one is just a faint glow.

On Monday, 7 November 2022 at 09:31:26 UTC, Brian Gaff wrote:
> LEDs can easily remain on purely by induced voltages along wires close to
> each other. Not much you can do but some of them have a small bleed resistor
> inside that makes them discharge anything that might otherwise make them
> glow eerily.
> Neons in pieces of gear back in the day used to glow purely by the pick up
> in the wiring loom, Once again a resistor of around 470k fixed it.
> Brian
>
> --
>
> --:
> This newsgroup posting comes to you directly from...
> The Sofa of Brian Gaff...
> bri...@blueyonder.co.uk
> Blind user, so no pictures please
> Note this Signature is meaningless.!
> "GB" <NOTso...@microsoft.invalid> wrote in message
> news:tk935f$39kgf$2...@dont-email.me...
> > On 05/11/2022 13:31, Dave Plowman (News) wrote:
> >> In article <20221104180...@jrenewsid.jretrading.com>,
> >> Joe <j...@jretrading.com> wrote:
> >>>> Doesn't it depend on the circuitry in the base of the bulb? For
> >>>> example if there is a capacitor in there that holds charge for a few
> >>>> moments after the power is turned off, the bulb will continue to glow
> >>>> until that capacitor loses all its charge through the bulb. Other
> >>>> circuits may not have such a capacitor and the bulb extinguishes
> >>>> almost instantly.
> >>>>
> >>
> >>> Yes, but I wouldn't expect so. The power wasn't mentioned, but I'd
> >>> guess around 4-5W. About a third to half an Amp of current, depending
> >>> on how many LEDs. That's a hell of a capacitor.
> >>
> >> But does it stay at full brightness after the power is turned off? An LED
> >> will stay lit at a very small proportion of the full current, but
> >> obviously not at full level.
> >>
> >
> > My one is just a faint glow.

Also most LED are actually very small solar panel like and can produce up to 2V in bright lighting conditions.
There's a light flasher circuit in elekor mag using 2 x 10Meg resistors 2 x 100nf caps and a push switch.
Under office lighting conditions it takes about a miniute for the caps to charge and then pressing the switch you get a faint flash
of the LED. In reasonable sunlight it just takes a few seconds to charge.

On Sat, 5 Nov 2022 17:56:37 +0000
Max Demian <max_demian@bigfoot.com> wrote:

> Reminds me of the trick light bulbs that light up when you hold them
> in your hand. "Amaze your friends!" (Until they get so bored with
> your silly tricks that they aren't your friends any more.)
>
Apparently you can do the same by holding a fluorescent tube under a
high voltage distribution line.

On Sat, 12 Nov 2022 11:09:11 +1100, Rob Morley <nospam@ntlworld.com> wrote:

> On Sat, 5 Nov 2022 17:56:37 +0000
> Max Demian <max_demian@bigfoot.com> wrote:
>
>> Reminds me of the trick light bulbs that light up when you hold them
>> in your hand. "Amaze your friends!" (Until they get so bored with
>> your silly tricks that they aren't your friends any more.)
>>
> Apparently you can do the same by holding a fluorescent tube under a
> high voltage distribution line.

Not when the mains have failed.