sci.electronics.repair@googlegroups.com

Today's topics:

* Color changing LEDs - 3 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/0dbbdbcf6a7c8155?hl=en
* Task Light just Flickers - 5 messages, 4 authors
http://groups.google.com/group/sci.electronics.repair/t/200662dd1f69bd0a?hl=en
* - 1 message, 1 author
http://groups.google.com/group/sci.electronics.repair/t/?hl=en

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TOPIC: Color changing LEDs
http://groups.google.com/group/sci.electronics.repair/t/0dbbdbcf6a7c8155?hl=en
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== 1 of 3 ==
Date: Thurs, May 6 2010 12:44 am
From: "Phil Allison"

<mister_friendly@the-newzgroups.com>

>I keep seeing these little solar power sidewalk lights. Last year
> they were all white (blueish white). Lately I see them where they
> change color. Yet, they only have one LED. How can a LED change
> color?

** Bi-colour LEDS like this have been around for 30 years.

http://www.effled.com/images/products/bicolor-led/throughhole-led/3mm_Bin_Color_LED_RG.jpg

... Phil

== 2 of 3 ==
Date: Thurs, May 6 2010 6:13 am
From: Meat Plow

On Thu, 06 May 2010 01:20:36 -0500,
mister_friendly@the-newzgroups.comwrote:

>I keep seeing these little solar power sidewalk lights. Last year
>they were all white (blueish white). Lately I see them where they
>change color. Yet, they only have one LED. How can a LED change
>color? I thought the color was determined by dopeing it with a metal.
>So how can they change? This has me puzzled.

Bi-color LED have two LED inside with a common cathode. Change the
polarity and you switch on the other LED.

== 3 of 3 ==
Date: Thurs, May 6 2010 8:21 am
From: Cydrome Leader

Meat Plow <mhywatt@yahoo.com> wrote:
> On Thu, 06 May 2010 01:20:36 -0500,
> mister_friendly@the-newzgroups.comwrote:
>
>>I keep seeing these little solar power sidewalk lights. Last year
>>they were all white (blueish white). Lately I see them where they
>>change color. Yet, they only have one LED. How can a LED change
>>color? I thought the color was determined by dopeing it with a metal.
>>So how can they change? This has me puzzled.
>
> Bi-color LED have two LED inside with a common cathode. Change the
> polarity and you switch on the other LED.

this probably has nothing to do with bicolor LEDs. Who the hell would make
a red/green sidewalk light anyways?

Anyways, white LEDs are sort of like flourescent lights. They junction
makes bright blue light and there is a phosphor that then converts this
into "white". Quite a bit of the blue leaks out.

The quality of white can vary (and does so more with cheap LEDs) in
addition to the phosphor actually aging.

so a visible color change from a cheap white LED isn't all that
surprising.

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TOPIC: Task Light just Flickers
http://groups.google.com/group/sci.electronics.repair/t/200662dd1f69bd0a?hl=en
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== 1 of 5 ==
Date: Thurs, May 6 2010 4:57 am
From: PeterD

On Thu, 6 May 2010 00:32:36 -0500, "don" <don@panix.com> wrote:

>I have a Luxo asymmetrical task light which takes an 18 watt bulb, which is
>starting to give me trouble. Most of the time it will just flicker as if it
>is trying to come on, but sometimes it will flicker once or twice and then
>come right on. When it does come on it shines bright. Luxo will not support
>this task light anymore because they say it is too old??? even though it
>was supposedly guaranteed for life. What is causing this intermittant
>problem and how could I fix it? I hate to throw the light out because it
>was around $200 when I bought it and it does work fine after it lights up.
>
>

Uh, did you replace the bulb?

== 2 of 5 ==
Date: Thurs, May 6 2010 5:04 am
From: "William Sommerwerck"

> Uh, did you replace the bulb?

Indeed. This sounds like an intermittent filament. Assuming it's an
incandescent lamp.

Is this a fluorescent lamp? It could be the bulb, or the "ballast".

== 3 of 5 ==
Date: Thurs, May 6 2010 5:09 am
From: "Geoffrey S. Mendelson"

> On Thu, 6 May 2010 00:32:36 -0500, "don" <don@panix.com> wrote:
>
>>I have a Luxo asymmetrical task light which takes an 18 watt bulb, which is
>>starting to give me trouble. Most of the time it will just flicker as if it
>>is trying to come on, but sometimes it will flicker once or twice and then
>>come right on.

PeterD wrote:

> Uh, did you replace the bulb?

Or the starter? I've had several bug zappers with replaceable bulbs, that
did not get fixed by replacing them. Then I decided to ignore the "no user
servicable parts inside" stickers, and opened them up. Inside was a regular
floursecent starter in a socket for each bulb.

I've replaced them each time I've replaced the bulbs, which makes a makes it
a $7 repair instead of a $40 replacement.

Yes, these are big bug zappers.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the situation.
i.e possessing less facts or information than can be found in the Wikipedia.

== 4 of 5 ==
Date: Thurs, May 6 2010 9:44 am
From: Smitty Two

In article <hrub8s$nus$1@news.eternal-september.org>,
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote:

> > Uh, did you replace the bulb?
>
> Indeed. This sounds like an intermittent filament. Assuming it's an
> incandescent lamp.
>
> Is this a fluorescent lamp? It could be the bulb, or the "ballast".

I haven't seen too many 18w incandescent lights ...

== 5 of 5 ==
Date: Thurs, May 6 2010 9:46 am
From: "William Sommerwerck"

>>> Uh, did you replace the bulb?

>> This sounds like an intermittent filament. Assuming it's an
>> incandescent lamp.
>> Is this a fluorescent lamp? It could be the bulb, or the "ballast".

> I haven't seen too many 18W incandescent lights ...

No, but there are low-wattage tungsten-halogen lamps used in such products.

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