What current is drawn by LED mains night light?

How much current is drawn by an LED night light which runs off the
mains?

BTW what sort of circuit is used for a LED to run off the mains. Is
it just a drop down resistor and a rectifier?


--
(The one I have also has a photocell to switch off the light in the
day but I don't think that bit of the circuit affects the current
drawn.)

Peter wrote:
> How much current is drawn by an LED night light which runs off the
> mains?
>

A web search engine would help. It shows the information right on your
computation machine :-)

This one is 250mW:

http://www.leviton.com/OA_HTML/ibeCC...&section=11773


> BTW what sort of circuit is used for a LED to run off the mains. Is
> it just a drop down resistor and a rectifier?
>

http://www.discovercircuits.com/H-Co...d-led-nite.htm

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

On Wed, 23 Sep 2009 13:37:22 -0700, Joerg <(E-Mail Removed)>
wrote:

><snip>
>http://www.discovercircuits.com/H-Co...d-led-nite.htm

The author there makes an interesting comment.

"... after only three months, the light gradually faded until it was
virtually useless. This has happened to me several times before with
other lights I have tried and results from the use of cheap inferior
white LEDs, which have phosphors that quickly fade."

I had no idea people were using phosphors that would be significantly
damaged by blue LED emissions. I am trying to understand exactly how
that would happen, besides. So I guess the author must mean that the
phosphors are simply chemically unstable to begin with.

Does anyone happen to know precisely which phosphor material is being
used in these "cheap inferior white LEDs," as the author wrote? I'd
like to know.

Jon

Jon Kirwan wrote:
> On Wed, 23 Sep 2009 13:37:22 -0700, Joerg <(E-Mail Removed)>
> wrote:
>
>> <snip>
>> http://www.discovercircuits.com/H-Co...d-led-nite.htm
>
> The author there makes an interesting comment.
>
> "... after only three months, the light gradually faded until it was
> virtually useless. This has happened to me several times before with
> other lights I have tried and results from the use of cheap inferior
> white LEDs, which have phosphors that quickly fade."

I suppose it depends how cheap and nasty your white LED supplier is. I
have had a white LED based night light running for best part of 5 years
and the amazing thing is that the minimum current required for a dark
adapted eye to see by is around 10uA. So in principle you could just run
a night lite off a capacitive divider and rectifier with a suitable
choke/resistor in series to protect the diode from any nasty transients
that come down the line. Power used by that at 3mW would be hard for a
normal mains electricity meter to detect.

Mine uses a 9v rechargable that lasts about a year in its standby state
- it will run as a torch if switched on. But it is never quite off which
makes the torch a lot easier to find if the power drops after dark.
>
> I had no idea people were using phosphors that would be significantly
> damaged by blue LED emissions. I am trying to understand exactly how
> that would happen, besides. So I guess the author must mean that the
> phosphors are simply chemically unstable to begin with.
>
> Does anyone happen to know precisely which phosphor material is being
> used in these "cheap inferior white LEDs," as the author wrote? I'd
> like to know.

It is a surprising claim. I expect there are some yellow organic dyes or
pigments like rubrene that do degrade fairly quickly under the influence
of blue to near UV light. But I'd be very surprised if the normal
inorganic phosphors of white LEDs ever failed in that way.

Question now is which brands of white LED are using unstable phosphors
(if any).

Regards,
Martin Brown

Jan Panteltje wrote:
> On a sunny day (Wed, 23 Sep 2009 21:06:53 +0100) it happened Peter
> <(E-Mail Removed)> wrote in
> <(E-Mail Removed)>:
>
>> How much current is drawn by an LED night light which runs off the
>> mains?
>
> I have one, it says 1W.
> Pretty bright though, it says 'Deco LED', and is made by Philips,
> maybe not really a night light.
>
>> BTW what sort of circuit is used for a LED to run off the mains. Is
>> it just a drop down resistor and a rectifier?
>
> No, I think it could be some switcher.


Hold an AM radio next to it, then you'll know.

[...]

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Jon Kirwan wrote:
> On Wed, 23 Sep 2009 13:37:22 -0700, Joerg <(E-Mail Removed)>
> wrote:
>
>> <snip>
>> http://www.discovercircuits.com/H-Co...d-led-nite.htm
>
> The author there makes an interesting comment.
>
> "... after only three months, the light gradually faded until it was
> virtually useless. This has happened to me several times before with
> other lights I have tried and results from the use of cheap inferior
> white LEDs, which have phosphors that quickly fade."
>
> I had no idea people were using phosphors that would be significantly
> damaged by blue LED emissions. I am trying to understand exactly how
> that would happen, besides. So I guess the author must mean that the
> phosphors are simply chemically unstable to begin with.
>
> Does anyone happen to know precisely which phosphor material is being
> used in these "cheap inferior white LEDs," as the author wrote? I'd
> like to know.
>

John Larkin once said that everything electronic that emits something
such as light doesn't live forever. On every project I was involved in
with serious LEDs on there lifetime was one of the agenda items to discuss.

I assume it's like with CFL. Our first round died within the year, well
short of their 10x light bulb claims. So I gave up on this technology
for many years. Then I tried again, this time Philips Marathon. They
seem to last forever.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

On Wed, 23 Sep 2009 14:47:04 -0700, Joerg wrote:
>
> I assume it's like with CFL. Our first round died within the year, well
> short of their 10x light bulb claims. So I gave up on this technology
> for many years. Then I tried again, this time Philips Marathon. They
> seem to last forever.

I saw one of those whiny "green" shows on "edjamacational" TeeVee, and
they said, "Don't throw incandescents in the trash. The glass takes
hundreds of years to break down."

What a bunch of idiots. Glass is ALREADY DIRT!!

Cheers!
Rich

John Larkin wrote:
> On Wed, 23 Sep 2009 14:47:04 -0700, Joerg <(E-Mail Removed)>
> wrote:
>
>> Jon Kirwan wrote:
>>> On Wed, 23 Sep 2009 13:37:22 -0700, Joerg <(E-Mail Removed)>
>>> wrote:
>>>
>>>> <snip>
>>>> http://www.discovercircuits.com/H-Co...d-led-nite.htm
>>> The author there makes an interesting comment.
>>>
>>> "... after only three months, the light gradually faded until it was
>>> virtually useless. This has happened to me several times before with
>>> other lights I have tried and results from the use of cheap inferior
>>> white LEDs, which have phosphors that quickly fade."
>
> They should still emit a bunch of blue.
>
>>> I had no idea people were using phosphors that would be significantly
>>> damaged by blue LED emissions. I am trying to understand exactly how
>>> that would happen, besides. So I guess the author must mean that the
>>> phosphors are simply chemically unstable to begin with.
>>>
>>> Does anyone happen to know precisely which phosphor material is being
>>> used in these "cheap inferior white LEDs," as the author wrote? I'd
>>> like to know.
>>>
>> John Larkin once said that everything electronic that emits something
>> such as light doesn't live forever. On every project I was involved in
>> with serious LEDs on there lifetime was one of the agenda items to discuss.
>
> I bought a bunch of cool blue led night lights, a year or so ago, and
> set one aside as a reference to check against once in a while. No
> visible diff so far. Must have got lucky.
>

Blue for a night light? Yuck.


> Neons usually last a few years. ELs fade and do other weird things.
>

We still use the little incandescent ones. They last several years and
have a nice spectrum.


>> I assume it's like with CFL. Our first round died within the year, well
>> short of their 10x light bulb claims. So I gave up on this technology
>> for many years. Then I tried again, this time Philips Marathon. They
>> seem to last forever.
>
> If they're left on all the time, they last a lot more than if they're
> cycled. 7 watts isn't a lot of power to leave on.
>

I think they have 14W or so. But they are way too bright as a night
light. Also, these don't seem to mind cycling and their brightness is
usable right after turn-on (except in winter). The CFL flood light
outdoors, different thing. Easily takes a minute to get from near-IR to
white. Or several minutes in winter.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

On Wed, 23 Sep 2009 14:47:04 -0700, Joerg <(E-Mail Removed)>
wrote:

>Jon Kirwan wrote:
>> On Wed, 23 Sep 2009 13:37:22 -0700, Joerg <(E-Mail Removed)>
>> wrote:
>>
>>> <snip>
>>> http://www.discovercircuits.com/H-Co...d-led-nite.htm
>>
>> The author there makes an interesting comment.
>>
>> "... after only three months, the light gradually faded until it was
>> virtually useless. This has happened to me several times before with
>> other lights I have tried and results from the use of cheap inferior
>> white LEDs, which have phosphors that quickly fade."
>>
>> I had no idea people were using phosphors that would be significantly
>> damaged by blue LED emissions. I am trying to understand exactly how
>> that would happen, besides. So I guess the author must mean that the
>> phosphors are simply chemically unstable to begin with.
>>
>> Does anyone happen to know precisely which phosphor material is being
>> used in these "cheap inferior white LEDs," as the author wrote? I'd
>> like to know.
>
>John Larkin once said that everything electronic that emits something
>such as light doesn't live forever. On every project I was involved in
>with serious LEDs on there lifetime was one of the agenda items to discuss.
>
>I assume it's like with CFL. Our first round died within the year, well
>short of their 10x light bulb claims. So I gave up on this technology
>for many years. Then I tried again, this time Philips Marathon. They
>seem to last forever.

Well, I didn't want to be as vague as all that. I work with rare
earth phosphors, regularly. And they are pretty hardy materials,
fired usually at highish temperatures and not prone to changing
structure by the fly-speck energies found in near-400nm photon. I
mean, this is only 3eV or so. Most I've worked with are fine at 5eV
almost forever.

I find Martin's response just about exactly how I feel about it. There
are organic/laser dyes that do degrade. But these aren't what I
thought they were using in white LEDs. As he points out in what I
consider to be broad agreement with me, rare earth ceramic/inorganic
phosphors pretty much just work all day long.

I think the LED itself can indeed fail. But not the phosphor. That's
hard for me to imagine, right now. In the case you talk about with
CFLs, I've opened up just about every CFL that has ever failed in my
home and taken a close look -- dismantling every single part, in fact.
There is a particular brand I find to have very dangerous designs (it
is sold at Costco) and those burn up for just about every imaginable
reason. I've had capacitors explode and burn, transistors literally
blow their sides out, inductors which overheated and caught fire, etc.
I think they under-design the entire thing. It's all at risk. On the
other hand, as you say, the Marathon units are much better designed.
hehe. In fact, they also use a more complex method to actually attach
the circuit board between the screw end and the bulb that makes it
harder for me to gain access, too. But when they fail, it seems to be
that the parts do NOT burn up. (I've only had two fail so far from
them and I think both cases related to the fluorescent bulb itself --
but NOT the failure of its phosphor material.)

Jon

On Wed, 23 Sep 2009 14:42:56 -0700, Joerg <(E-Mail Removed)>
wrote:

>Jan Panteltje wrote:
>> On a sunny day (Wed, 23 Sep 2009 21:06:53 +0100) it happened Peter
>> <(E-Mail Removed)> wrote in
>> <(E-Mail Removed)>:
>>
>>> How much current is drawn by an LED night light which runs off the
>>> mains?
>>
>> I have one, it says 1W.
>> Pretty bright though, it says 'Deco LED', and is made by Philips,
>> maybe not really a night light.
>>
>>> BTW what sort of circuit is used for a LED to run off the mains. Is
>>> it just a drop down resistor and a rectifier?
>>
>> No, I think it could be some switcher.
>
>Hold an AM radio next to it, then you'll know.
>
>[...]

Now that's how I used to "listen" to my software operating on the
Altair 8800! Wonderful way to detect loops, etc.

Jon