Do you have a question? Post it now! No Registration Necessary
March 21, 2016, 5:30 pm

The LED in my flashlight is blinking (2/sec). It?s not the support
circuitry (constant current): the voltage across the LED is constant 4v. I
presume it?s a failure mode of the LED. It happens immediately upon
power-on.
http://imgur.com/a/rIRDG
The form-factor is close to a 5x5mm (h x diam). Standard through-hole leads.
But it?s a pretty high-intensity one. Don?t know what makes it so, but I
classify anything with a yellow square visible in the center as
?high-intensity?. Maybe not technically accurate, but there you are.
What I?ve found so far is either a standard 5mm LED but not very bright, or
SMD types requiring heat sinks.
It?s a great little light, and I?ve not found anything as small,
long-lasting, with single AA that I like as much. And this is a learning
experience, so there?s that.
Any pointers to a suitable replacement LED would be appreciated.
Thanks.
circuitry (constant current): the voltage across the LED is constant 4v. I
presume it?s a failure mode of the LED. It happens immediately upon
power-on.
http://imgur.com/a/rIRDG
The form-factor is close to a 5x5mm (h x diam). Standard through-hole leads.
But it?s a pretty high-intensity one. Don?t know what makes it so, but I
classify anything with a yellow square visible in the center as
?high-intensity?. Maybe not technically accurate, but there you are.
What I?ve found so far is either a standard 5mm LED but not very bright, or
SMD types requiring heat sinks.
It?s a great little light, and I?ve not found anything as small,
long-lasting, with single AA that I like as much. And this is a learning
experience, so there?s that.
Any pointers to a suitable replacement LED would be appreciated.
Thanks.

Re: Replacement LED?


I beg to differ with your diagnosis. Unless the LED has magically
turned into a thermostat controlled flasher, it's not going to do
that. More likely, the LED driver circuit is doing the flashing.
Based on zero detail about the actual flashlight, my wild guess(tm)
would be the big electrolytic that usually goes across the battery.
Broken or badly soldered connections on the driver PCB are also
likely.


If it's not too much trouble, could you disclose the maker and model
number of your flashlight? Extra credit for providing a link to the
manufactures web site or China source link. If there are no numbers
or sources, perhaps a photo of the assembled flashlight?

Yep. You're looking at the wrong stuff. Maybe something by Cree:
<http://www.cree.com/LED-Components-and-Modules/Products
Nope. Ok, I give up. What the photo looks like is a common dome
shaped LED (as in the Cree URL above) with a lens over it. I did some
Googling looking for the lens and couldn't find it.

I have one that meets your requirements. L3 Illumination L10:
<http://www.candlepowerforums.com/vb/showthread.php?376058-L3-Illumination-L10-%28XP-G2-R5-or-Nichia-219-1xAA%29-Review-RUNTIMES-BEAMS-VIDEO
Single cell, very bright, tolerably priced, small, adjustable
brightness, etc. However, there's a catch. It has 4 brightness
levels set by twisting the two sections of the body. No problem
except that it makes it a two handed operation. I would have
preferred a push button at the back end. I've also measured the
brightness (using my highly creative and non-standard procedure) at
about 90-110 lumens (varies with temperature).

Again, I don't think it's the LED. The driver board is a more likely
culprit. Put it under a magnifier and see if you can find the broken
trace. Put a light behind the PCB to make it easier to see the break.
If desperate, trace out the schematic and try to identify the LED
controller chip. If it uses an MLCC capacitor, use a hot air gun to
reflow, not a soldering iron tip.
You might also get some help in CandlePowerForums:
<http://www.candlepowerforums.com
Good luck.
--
Jeff Liebermann snipped-for-privacy@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Jeff Liebermann snipped-for-privacy@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
We've slightly trimmed the long signature. Click to see the full one.

Re: Replacement LED?

Nebo NU15J:
https://www.nebotools.com/prod_details.php?id31%&cid16%&subid94%&subsubcid=
I like this model for its good trade-off between brightness and battery life.
Might be ?better?, but this fits my needs. (And it ft fits in my pocket
along with my micro Swiss army knife...)
No controller chip. Looks like a boost converter (inductor, BJT, schottky
diode, ceramic cap).
I scoped the voltage across the LED: it's constant 4v (with a very
small--20mv?--rise and fall as it switches on and off). Haven?t yet
measured current. Surely if there was a bad solder joint or other failure it
would show up here.
Thanks for the referrals of other lights, but I?m not buying a replacement.
I?m doing this for fun and to learn.
Cheers.

Re: Replacement LED?

Looks like the flashing LED is a common problem:
<http://www.candlepowerforums.com/vb/showthread.php?417142-Replacement-LED

Some day, someone will design a flashlight with an automatic PWM light
dimmer. Shine the light at something bright, and the flashlight runs
at full brightness. Shine it at something in the dark, and it goes to
fairly dim.

Yep, that's about it. No controller.


Ok, I'm wrong. The flashing is not caused by the non-existent
controller chip.
Like I mumbled previously, see if there's a dome type LED under a
plastic lens. You'll probably need to unsolder the LED leads to do
this. If they really are two parts, it should be possible to find a
replacement LED.
If you can't identify the LED by the power output, try measuring the
current drain with a new battery. Multiply the current with your
measured 4V, and you should get the power in watts. That should tell
you if you should be looking for a 1/2, 1, or 1.5v LED.
--
Jeff Liebermann snipped-for-privacy@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Jeff Liebermann snipped-for-privacy@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
We've slightly trimmed the long signature. Click to see the full one.

Re: Replacement LED?

Oops(tm).

Oops 2.0(tm). I was in a rush to get out of door. Sorry. Also, I
just noticed that there is no such thing as an individual 1.5w LED.
--
Jeff Liebermann snipped-for-privacy@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Jeff Liebermann snipped-for-privacy@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
We've slightly trimmed the long signature. Click to see the full one.

Re: Replacement LED?

Sounds about right. If you can light it up, just measure the battery
current drain, and calculate or estimate the power dissipation.

If you can remove what I believe to be a lens, I think you'll find
that the actual LED is rather conventional and can be found in the
Cree catalog.
<http://www.cree.com/LED-Components-and-Modules/Products
If you sort the above list by power output, there are only 3ea 1w
LED's listed. Just find the right die size and good luck soldering
the tiny chip. You can also dig throught the current flashlight
offerings and see which 1w chips are popular.

Learn by Destroying.... then buy a new flashlight.
--
Jeff Liebermann snipped-for-privacy@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Jeff Liebermann snipped-for-privacy@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
We've slightly trimmed the long signature. Click to see the full one.

Re: Replacement LED?

Please deduct one point for spelling my name wrong.

No. I thought you said your flashlight was bright and possibly 1
watt. Those are common 5mm LED's with 0.5 watts maximum.
<https://www.google.com/search?q=5mm+white+led+0.5+watts
These photos look very much like what I would expect to be hiding
under what I believe to be a lens of some sorts:
<https://www.google.com/search?q=5mm+white+led+0.5+watts&tbm=isch
This looks a bit closer:
<http://www.ebay.com/itm/161246348498
That data sheet is also slightly insane, specifying the luminous flux
as:
Lumen typ.: 19 mcd
Lumens are measured in umm.... lumens, not millicandelas. It is
possible to convert between lumens and mcd's using the viewing angle:
<http://www.rapidtables.com/calc/light/mcd-to-lumen-calculator.htm
Anyway, 19 lumens is not very bright but probably good enough for a
pocket flashlight.
--
Jeff Liebermann snipped-for-privacy@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Jeff Liebermann snipped-for-privacy@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
We've slightly trimmed the long signature. Click to see the full one.

Re: Replacement LED?

And I tried so hard to get the ?Lei/Lie? bit right! (c; 2 steps forward,
1 step back...

One of those images (located here):
http://tinyurl.com/j4pwvuw
looks exactly like the one in my light. It?s squat, with very (relatively)
large yellow die(?) in the center. I don?t think there?s a separate lens.
Maybe it?s molded to focus the light (integral lens)?
Wish I could find that LED other than @ Alibaba...
Ah-HAH! From that Alibaba image page: ?strawhat LED?. Search turns up
similar-looking LEDs. Searching on the terms ?strawhat? and ?dimple?
tells me that this form-factor is for radial distribution of the light, not
throwing a beam. Which means the flashlight designer wanted the reflector to
shape the beam, not the LED.
So I?m looking for one of these types.
Thanks.
(Why are my search skills so crap? Google keeps returning Manga images and
cartoon faces...)

Re: Replacement LED?

Hmm, that sounds like a good idea to put in my planned LED torch project,
which was going to have a manual dimmer anyway. I guess an LDR would be
suitable? Maybe mount it in a small tube to make it directional?
I guess I'll have to find an LDR and wave it around with my multimeter
attached. Ahh, the dignity of research. :)
--
__ __
#_ < |\| |< _#
__ __
#_ < |\| |< _#

Re: Replacement LED?
On 22/03/2016 03:51, Jeff Liebermann wrote:
<snip>

Thermostat controlled flasher is probably the exact description. It
happens when LEDs are driven straight from batteries too, and is
probably the bond wire heating and cooling making intermittent contact
at a few Hz.
I have a cheap LED torch which uses nine parallel connected white LEDs
running directly from 3 AAs. After a battery replacement, one is out,
four flash at different rates, and four are on.
Cheers
<snip>

Thermostat controlled flasher is probably the exact description. It
happens when LEDs are driven straight from batteries too, and is
probably the bond wire heating and cooling making intermittent contact
at a few Hz.
I have a cheap LED torch which uses nine parallel connected white LEDs
running directly from 3 AAs. After a battery replacement, one is out,
four flash at different rates, and four are on.
Cheers
--
Syd
Syd

Re: Replacement LED?
Circuit:
http://imgur.com/YeELiHI
which is identical to the application note in the datasheet (scroll down to
the ME2108A diagrams):
http://img.ozdisan.com/ETicaret_Dosya/431770_1622138.pdf
(easily translated via Google, but a bit more confusing...)
Measured current at the battery terminals is 275 mA (due to meter insertion
loss it?s difficult to get an accurate current reading at the LED?s
terminals--the LED dims). Voltage across the LED is a pretty-constant 4v.
Estimating the efficiency of the converter at (roughly) 75 percent the LED is
using 825 mW.
I guess I?m looking for a 1W replacement?
How?s my math?
Thanks.
http://imgur.com/YeELiHI
which is identical to the application note in the datasheet (scroll down to
the ME2108A diagrams):
http://img.ozdisan.com/ETicaret_Dosya/431770_1622138.pdf
(easily translated via Google, but a bit more confusing...)
Measured current at the battery terminals is 275 mA (due to meter insertion
loss it?s difficult to get an accurate current reading at the LED?s
terminals--the LED dims). Voltage across the LED is a pretty-constant 4v.
Estimating the efficiency of the converter at (roughly) 75 percent the LED is
using 825 mW.
I guess I?m looking for a 1W replacement?
How?s my math?
Thanks.
Site Timeline
- » Help with SMB BJT identification?
- — Next thread in » Electronic Components
-
- » MSI 945P.
- — Previous thread in » Electronic Components
-
- » Timing relay providers
- — Newest thread in » Electronic Components
-
- » Atmel 328 ext. interupts
- — The site's Newest Thread. Posted in » Electronics Design
-
- » Atmel 328 ext. interupts
- — The site's Last Updated Thread. Posted in » Embedded Programming
-