Replacement LED?

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.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 3/21/2016 1:30 PM, DaveC wrote:

So it has a boost SMPS?
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload





That's probably a downconversion phosphor. White LEDs are really blue LEDs with a blob of epoxy on top, loaded with yag powder that converts some of the blue to yellow.
--

John Larkin Highland Technology, Inc

lunatic fringe electronics
  Click to see the full signature.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload



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
  Click to see the full signature.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Nebo NU15J:
https://www.nebotools.com/prod_details.php?id1&cid &subid”&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.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 22/03/2016 05:56, DaveC wrote:

Desolder the original LED, carefully , as balance of probability it will be fine. Jumper in any old high power LED and see if that flashes too.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Looks like the flashing LED is a common problem: <http://www.candlepowerforums.com/vb/showthread.php?417142-Replacement-LED >I like this model for its good trade-off between brightness and battery life.
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
  Click to see the full signature.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Jeff Liebermann sez:

That?s my post on canblepowerforums.com. (c:

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.
Will do.

You mean 1/2, 1, or 1.5 *watt* LED, yes?
Thanks.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload


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
  Click to see the full signature.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I think this is an under-used(?) 1W LED.
unit. That way can dissipate some W.
But that presents its own set of problems. Optics will need to be matched to the new LED.
Hmm...
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
  Click to see the full signature.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

[Jeff Lieberman]
I found these:
https://www.led-tech.de/en/0.5W-Power-LEDs_DB-86.pdf
Looks good, no?
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
  Click to see the full signature.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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...)
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 22/03/2016 03:51, Jeff Liebermann wrote:
<snip> > I beg to differ with your diagnosis. Unless the LED has magically

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

Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 3/22/2016 4:41 PM, DaveC wrote:

Didn't you say it used a *single* 1.5 volt AA cell? I think that would make it 412 milliwatts not counting the conversion efficiency, so more likely a 1/2 watt LED.
--

Rick

Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 22 Mar 2016, rickman wrote

1.5v boosted to 4v (measured) output from the converter. 275 mA (measured) at the battery terminals. I make that to be 1100 mW. If presume 75 percent efficiency, 825 mW.
No?
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 3/22/2016 10:00 PM, DaveC wrote:

Perhaps I am missing something. The battery terminals will be at the battery voltage, no? So why would you use 4 volts which is at the output? It would be 4 volts times the LED current or the battery voltage times the input current.
--

Rick

Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Rick
Yikes! Of course you?re right.
Thanks.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.