| |
 |
|
|
Science Forum Index » Engineering - Lighting Forum » Repairing LEDs in situ....
Page 1 of 1
|
| Author |
Message |
| BigClive... |
 Posted: Sat Jun 14, 2008 4:12 pm |
|
|
|
Guest
|
Sorry. A rather wild title I know, but bear with me....
Those of you who suffered the early Chinese Gallium Nitride LEDs will
know that it wasn't uncommon for a random selection to fail
prematurely by flickering, going out or getting progressively dimmer.
I'm guessing that most of these issues were caused by film faults, and
interestingly latter LEDs from the same type of factories (bang 'em
out cheap) displayed a new characteristic where they would fail by
suddenly going out, but could be brought back to life by applying a
pulse of current across them, which I guess may be along the same
lines as "self healing" capacitors.
This could explain the common use of large parallel arrays of LEDs in
cheap products where an LED failing in this manner would suddenly sink
the large communal current of the parallel array and "clear" itself or
just blow completely allowing normal operation of the rest of the
array.
It follows that while building a prototype LED array I was using some
cheap ebay LEDs to test the design and was annoyed that one of the
blue's duly failed. It was one of three, but the series resistor
obviously limited the current to a level too low to do the deed on the
bad LED. With that in mind I pondered whether I could give the rogue
LED a jab with an external power supply without damaging either the
rogue LED or adjacent circuitry. It suddenly struck me that if I
applied a voltage lower then the bad LEDs normal forward voltage
across it, then it might blow clear then once it was operating again
the forward voltage would be too high for excess current to flow and
cause damage. I duly applied 2V current limited to about 1A across it
and the thing duly proceeded to work again!
I should add that it's been fine since, although I wouldn't bet my
life on it's future reliability. That said, I did the same to a loose
rogue LED a while back and then left it on 24/7 test and it never
failed again!
So in short, a quick fix fro a bad LED in a panel might be to use a
single AA cell and a couple of bits of wire to "Frankenstein" it back
to life.
Not recommended for a commercial environment, but OK for home stuff.
I see this place is still besieged with spam! |
|
|
| Back to top |
|
| Jeff Engel... |
| Posted: Sun Jun 15, 2008 8:04 am |
|
|
|
Guest
|
Hello Clive
Good to hear from you again. By comparison, my ISP's newsgroup server
has somehow filtered a lot of the spam that was flooding us a few months
ago.
BigClive :
Quote:
So in short, a quick fix fro a bad LED in a panel might be to use a
single AA cell and a couple of bits of wire to "Frankenstein" it back
to life.
Not recommended for a commercial environment, but OK for home stuff.
I see this place is still besieged with spam! |
|
|
| Back to top |
|
| BigClive... |
| Posted: Sun Jun 15, 2008 9:13 am |
|
|
|
Guest
|
On Jun 15, 3:19 pm, and... at (no spam) cucumber.demon.co.uk (Andrew Gabriel)
wrote:
Quote: In article <-rqdnTARRoNzj8jVnZ2dnUVZ_uOdn... at (no spam) comcast.com>,
Jeff Engel <searcher... at (no spam) comcast.net> writes:
Hello Clive
Good to hear from you again. By comparison, my ISP's newsgroup server
has somehow filtered a lot of the spam that was flooding us a few months
ago.
I'm not seeing any spam either.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
I'm using Gmail to view the groups at the moment. While Gmail is
great at filtering the spam on the mail it leaves it intact on the
newsgroups.
By the way, I hope you're not hosting much on your old Demon account
Gabriel. If you are I'd suggest moving it to another provider
immediately and replacing the Demon site with redirection pages until
it's not needed any more.
Lets just say that bigclive.com is NOT hosted on Demon (Thus) any
more..... |
|
|
| Back to top |
|
| Andrew Gabriel... |
| Posted: Sun Jun 15, 2008 9:19 am |
|
|
|
Guest
|
In article <-rqdnTARRoNzj8jVnZ2dnUVZ_uOdnZ2d at (no spam) comcast.com>,
Jeff Engel <searcher623 at (no spam) comcast.net> writes:
Quote: Hello Clive
Good to hear from you again. By comparison, my ISP's newsgroup server
has somehow filtered a lot of the spam that was flooding us a few months
ago.
I'm not seeing any spam either.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup] |
|
|
| Back to top |
|
| Andrew Gabriel... |
| Posted: Sun Jun 15, 2008 2:51 pm |
|
|
|
Guest
|
In article <9991a851-3a55-4c59-9e4b-ee2d26b9038c at (no spam) c58g2000hsc.googlegroups.com>,
BigClive <bigclive1 at (no spam) googlemail.com> writes:
Quote: On Jun 15, 3:19 pm, and... at (no spam) cucumber.demon.co.uk (Andrew Gabriel)
wrote:
In article <-rqdnTARRoNzj8jVnZ2dnUVZ_uOdn... at (no spam) comcast.com>,
Jeff Engel <searcher... at (no spam) comcast.net> writes:
Hello Clive
Good to hear from you again. By comparison, my ISP's newsgroup server
has somehow filtered a lot of the spam that was flooding us a few months
ago.
I'm not seeing any spam either.
I'm using Gmail to view the groups at the moment. While Gmail is
great at filtering the spam on the mail it leaves it intact on the
newsgroups.
By the way, I hope you're not hosting much on your old Demon account
Gabriel. If you are I'd suggest moving it to another provider
immediately and replacing the Demon site with redirection pages until
it's not needed any more.
Lets just say that bigclive.com is NOT hosted on Demon (Thus) any
more.....
Yes, I must move it off. I haven't used Demon as my ISP for
about 8 years, but I do still have the web pages and email
through them. I think they're in the final death throws - I
get the impression they've got no one technical left there,
combined with an anchient infrastructure which has collapsed.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup] |
|
|
| Back to top |
|
| Adam Aglionby... |
| Posted: Sun Jun 15, 2008 4:22 pm |
|
|
|
Guest
|
On Jun 15, 3:12 am, BigClive <bigcli... at (no spam) googlemail.com> wrote:
Quote: Sorry. A rather wild title I know, but bear with me....
Those of you who suffered the early Chinese Gallium Nitride LEDs will
know that it wasn't uncommon for a random selection to fail
prematurely by flickering, going out or getting progressively dimmer.
I'm guessing that most of these issues were caused by film faults, and
interestingly latter LEDs from the same type of factories (bang 'em
out cheap) displayed a new characteristic where they would fail by
suddenly going out, but could be brought back to life by applying a
pulse of current across them, which I guess may be along the same
lines as "self healing" capacitors.
This could explain the common use of large parallel arrays of LEDs in
cheap products where an LED failing in this manner would suddenly sink
the large communal current of the parallel array and "clear" itself or
just blow completely allowing normal operation of the rest of the
array.
It follows that while building a prototype LED array I was using some
cheap ebay LEDs to test the design and was annoyed that one of the
blue's duly failed. It was one of three, but the series resistor
obviously limited the current to a level too low to do the deed on the
bad LED. With that in mind I pondered whether I could give the rogue
LED a jab with an external power supply without damaging either the
rogue LED or adjacent circuitry. It suddenly struck me that if I
applied a voltage lower then the bad LEDs normal forward voltage
across it, then it might blow clear then once it was operating again
the forward voltage would be too high for excess current to flow and
cause damage. I duly applied 2V current limited to about 1A across it
and the thing duly proceeded to work again!
I should add that it's been fine since, although I wouldn't bet my
life on it's future reliability. That said, I did the same to a loose
rogue LED a while back and then left it on 24/7 test and it never
failed again!
So in short, a quick fix fro a bad LED in a panel might be to use a
single AA cell and a couple of bits of wire to "Frankenstein" it back
to life.
Not recommended for a commercial environment, but OK for home stuff.
I see this place is still besieged with spam!
I did that a while back even with some white Nichias expensive,at the
time, remember 4 quid an LED, blatting them with overvoltage would
ressurrect them , wondered wether it was a bond wire thing.
dont see any spam on sci.engr.lighting using google groups as well and
muppet with Mi5 fixation appears to have taken a walk in the woods...
Adam
P.S. LED Par36s surving well |
|
|
| Back to top |
|
| LightingMan... |
| Posted: Sun Jun 22, 2008 12:20 pm |
|
|
|
Guest
|
Hi Big Clive
I was so pleased to see you on this forum! I love your webpage "Big
Clive's Things to make and do!!!" I'm an old fan and have visited
your website from time to time for years to see what you're up to!
One of my recent favourites is your mains chandelier - absolutely
fantastic!!
- Lightingman
(Off to your website now as I see you've got something new about
remote lighting of fireworks!!) |
|
|
| Back to top |
|
| BigClive... |
| Posted: Wed Jun 25, 2008 12:30 pm |
|
|
|
Guest
|
On Jun 22, 11:20 pm, LightingMan <Tartuf... at (no spam) gmail.com> wrote:
Quote: Hi Big Clive
I was so pleased to see you on this forum! I love your webpage "Big
Clive's Things to make and do!!!" I'm an old fan and have visited
your website from time to time for years to see what you're up to!
One of my recent favourites is your mains chandelier - absolutely
fantastic!!
- Lightingman
(Off to your website now as I see you've got something new about
remote lighting of fireworks!!)
Thanks, hope you've not been disappointed at the lack of new
projects. I've just not been keeping the site up to date these days.
Demon forced me to rethink that though when they took my site down
completely, hence the pointers from their space to the new space.
They suddenly decided to enforce the 2.5GB traffic rule without
warning and simply had no upgrade option for the older demon domain
names. Lots of calls to Indian call centres who sort of tried to find
a stock answer but couldn't.
I've got a couple of new LED projects impending. The matching circuit
boards are currently on their way from the manufacturer! An RGB
floodlight assembly and a new style of RGB controller. You'll see
when I put it up.
The remote lighting of fireworks project is a lot of fun. I
guarantee, your workshop will stink of cremated resistors when you
give it a go. One resistor is not enough. ;)
www.bigclive.com/ignite.htm |
|
|
| Back to top |
|
| |
|
Page 1 of 1
All times are GMT - 5 Hours
The time now is Fri Dec 05, 2008 9:20 am
|
|