Replacement LED?

DaveC · Mar 21, 2016

The LED in my flashlight is blinking (2/sec). Itâs not the support
circuitry (constant current): the voltage across the LED is constant 4v. I
presume itâs 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 itâs a pretty high-intensity one. Donât know what makes it so, but I
classify anything with a yellow square visible in the center as
âhigh-intensityâ. Maybe not technically accurate, but there you are.

What Iâve found so far is either a standard 5mm LED but not very bright, or
SMD types requiring heat sinks.

Itâs a great little light, and Iâve not found anything as small,
long-lasting, with single AA that I like as much. And this is a learning
experience, so thereâs that.

Any pointers to a suitable replacement LED would be appreciated.

Thanks.

pfjw@aol.com · Mar 21, 2016

On Monday, March 21, 2016 at 1:30:08 PM UTC-4, DaveC wrote:

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.

So, its mot a Maglite? That about covers the "suitable replacement" question. That light was never meant to be serviced, and so your best bet in terms of time/cost/effort, together with the inevitable PITA factor is to simply replace the light altogether.

Peter Wieck
Melrose Park, PA

p.s.: Only Maglites permitted in this household.

Cursitor Doom · Mar 21, 2016

On Mon, 21 Mar 2016 13:10:09 -0700, pfjw@aol.com wrote:

> p.s.: Only Maglites permitted in this household.

Make good billy clubs, the larger ones. :->

pfjw@aol.com · Mar 22, 2016

Maglite makes LED units as well. The also stand behind their products....

Peter Wieck
Melrose Park, PA

Gareth Magennis · Mar 22, 2016

wrote in message
news:e658aab4-4e65-4e77-8c26-0937bb55aceb@googlegroups.com...

On Monday, March 21, 2016 at 1:30:08 PM UTC-4, DaveC wrote:

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.

So, its mot a Maglite? That about covers the "suitable replacement"
question. That light was never meant to be serviced, and so your best bet in
terms of time/cost/effort, together with the inevitable PITA factor is to
simply replace the light altogether.

Peter Wieck
Melrose Park, PA

p.s.: Only Maglites permitted in this household.

I used to use Maglites, til LED torches came on the scene.

No way I would buy a Maglite now.

Gareth.

Bob Engelhardt · Mar 22, 2016

On 3/21/2016 1:30 PM, DaveC wrote:

... the voltage across the LED is constant 4v.
... with single AA ...

So it has a boost SMPS?

Gareth Magennis · Mar 22, 2016

"Gareth Magennis" wrote in message news:xUYHy.69876$jz.53865@fx41.am4...

wrote in message
news:e658aab4-4e65-4e77-8c26-0937bb55aceb@googlegroups.com...

On Monday, March 21, 2016 at 1:30:08 PM UTC-4, DaveC wrote:

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.

So, its mot a Maglite? That about covers the "suitable replacement"
question. That light was never meant to be serviced, and so your best bet in
terms of time/cost/effort, together with the inevitable PITA factor is to
simply replace the light altogether.

Peter Wieck
Melrose Park, PA

p.s.: Only Maglites permitted in this household.

I used to use Maglites, til LED torches came on the scene.

No way I would buy a Maglite now.

Gareth.

Oops, just discovered Maglite do LED's.

My old MiniMaglite wouldn't do 2 gigs on one set of batteries, and I would
regularly have to replace the bulb too, and the switch would always need
maintenance.
Very expensive running costs, very time consuming, but good for hammering in
nails etc.

Gareth.

John Larkin · Mar 22, 2016

On Mon, 21 Mar 2016 10:30:03 -0700, DaveC <not@home.cow> wrote:

The LED in my flashlight is blinking (2/sec). Its not the support
circuitry (constant current): the voltage across the LED is constant 4v. I
presume its 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 its a pretty high-intensity one. Dont 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.

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

Phil Allison · Mar 22, 2016

Jeff Liebermann wrote:

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.

** The OP is probably correct and I have seen the same symptoms with 3mm red LEDs. Over time, excess DC current damages the LED chips and they intermittently drop light output and blink on and off.

Caused havoc in a Mesa Boogie amplifier when most of the dropping resistors for the 20 odd LED/CdS cell opto-couplers were the wrong value, by a factor of 10, resulting in almost 100mA of drive current.

..... Phil

Jeff Liebermann · Mar 22, 2016

On Mon, 21 Mar 2016 10:30:03 -0700, DaveC <not@home.cow> wrote:

The LED in my flashlight is blinking (2/sec). Its not the support
circuitry (constant current): the voltage across the LED is constant 4v. I
presume its a failure mode of the LED. It happens immediately upon
power-on.

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.

http://imgur.com/a/rIRDG
The form-factor is close to a 5x5mm (h x diam). Standard through-hole leads.

But its a pretty high-intensity one. Dont 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.

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?

What Ive found so far is either a standard 5mm LED but not very bright, or
SMD types requiring heat sinks.

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.

Its a great little light, and Ive not found anything as small,
long-lasting, with single AA that I like as much. And this is a learning
experience, so theres that.

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).

>Any pointers to a suitable replacement LED would be appreciated.

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 jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

DaveC · Mar 22, 2016

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.

Nebo NU15J:

https://www.nebotools.com/prod_details.php?id=31&cid=16&subid=94&subsubcid=

I like this model for its good trade-off between brightness and battery life.
Might be âbetterâ, 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). Havenât 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 Iâm not buying a replacement.
Iâm doing this for fun and to learn.

Cheers.

Phil Allison · Mar 22, 2016

Syd Rumpo wrote:

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.

** Ahhh - so you have seen it really happen too !!!

Bit like sighting the Loch Ness Monster.

Bonding certainly seems to be involved and LEDs are very sensitive to high temps - way more than silicon semiconductors.

Gallium arsenide is even whimpier than Germanium, lifespan deteriorating quickly above room temp.

..... Phil

Syd Rumpo · Mar 22, 2016

On 22/03/2016 03:51, Jeff Liebermann wrote:

<snip>

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.

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

N_Cook · Mar 22, 2016

On 22/03/2016 05:56, DaveC wrote:

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.

Nebo NU15J:

https://www.nebotools.com/prod_details.php?id=31&cid=16&subid=94&subsubcid=

I like this model for its good trade-off between brightness and battery life.
Might be âbetterâ, 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). Havenât 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 Iâm not buying a replacement.
Iâm doing this for fun and to learn.

Cheers.

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.

DaveC · Mar 23, 2016

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 itâs difficult to get an accurate current reading at the LEDâs
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 Iâm looking for a 1W replacement?

Howâs my math?

Thanks.

Jeff Liebermann · Mar 23, 2016

On Mon, 21 Mar 2016 22:56:51 -0700, DaveC <not@home.cow> wrote:

Nebo NU15J:
https://www.nebotools.com/prod_details.php?id=31&cid=16&subid=94&subsubcid=

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.

No controller chip. Looks like a boost converter (inductor, BJT, schottky
diode, ceramic cap).

Yep, that's about it. No controller.

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). Havent yet
measured current. Surely if there was a bad solder joint or other failure it
would show up here.

Ok, I'm wrong. The flashing is not caused by the non-existent
controller chip.

Thanks for the referrals of other lights, but Im not buying a replacement.
Im doing this for fun and to learn.

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 jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

DaveC · Mar 23, 2016

Jeff Liebermann sez:

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

Thatâs my post on canblepowerforums.com. (c:
> 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.

Will do.

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.

You mean 1/2, 1, or 1.5 *watt* LED, yes?

Thanks.

Jeff Liebermann · Mar 23, 2016

On Tue, 22 Mar 2016 16:56:48 -0700, DaveC <not@home.cow> wrote:

Jeff Liebermann sez:

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

Thats my post on canblepowerforums.com. (c:

Oops(tm).

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.

Will do.

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.

You mean 1/2, 1, or 1.5 *watt* LED, yes?

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 jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

DaveC · Mar 23, 2016

> Also, I just noticed that there is no such thing as an individual 1.5w LED.

I think this is an under-used(?) 1W LED.

If I canĂ˘âŹâ˘t find a direct replacement IĂ˘âŹâ˘m considering flipping
the PCB itĂ˘âŹâ˘s soldered to and using the copper side to solder a SMD
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...

DaveC · Mar 23, 2016

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

Yikes! Of course youâre right.

Thanks.

Replacement LED?

DaveC

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