Emitter Swap Success... Sort of

Swapped out the emitter on my old Nitecore D10 and switched it out for a newer XM-L2 emitter, changing it from cool white to a nice neutral color. My only question is I've noticed something weird with the highest/turbo mode.. When turning it on to turbo it lasts a few seconds before fading and quickly shutting off. Every other mode from right below turbo to moonlight works perfectly fine without any issues whatsoever. Any issues what may cause this and if I can fix it? No chips were damaged in the process of swapping it out so it shouldn't be because of anything like that but it has me baffled as to why it would act this way only on turbo.

I'm no expert, but I'll bet that the new XM-L2 is sucking more juice than the driver can handle? What battery/cell are you using?

Chris

Using just a standard Eneloop AA battery. Even though this light was rated to support 14500 I have heard of some people having theirs stop functioning as a result and don't want to risk mine since these aren't in production anymore and are very difficult to find. I would think the Eneloop would be enough but maybe the new XM-L2 is pulling more juice? It's definitely not a short as the soldering was clean and nowhere close to the pill.

snowlover91 said:

Using just a standard Eneloop AA battery. Even though this light was rated to support 14500 I have heard of some people having theirs stop functioning as a result and don't want to risk mine since these aren't in production anymore and are very difficult to find. I would think the Eneloop would be enough but maybe the new XM-L2 is pulling more juice? It's definitely not a short as the soldering was clean and nowhere close to the pill.

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The Eneloops should be able to handle 3A easily, but the new LED with its higher current demand might be a mismatch for the original driver, which is used to seeing a lower load from the weaker original LED. Seems like something might be heating up and shutting down thermally, no?

Chris

It's quite possible, it does warm up a bit in the few brief seconds but nothing too bad. The lower levels seem perfectly fine and unaffected. I do know the brightness at low is much higher now with the new LED so perhaps it is drawing more current which is too much for the driver? The only way I can turn it back on when it shuts off at turbo is to unscrew and screw it back on, pressing the tail cap button/switch doesn't do anything at all.

What was the old emitter? If it was an XM-L, the swap should be fairly seamless. If it was an XP-G or XP-E or something else, then the voltage requirements for a particular brightness will be different. The driver wouldn't know this, so that's perhaps why you're seeing some weird stuff.

I think most drivers use a current-based feedback loop, hence current-controlled. So if the driver was set to produce 350mA it will be the same for both the old and the new LED. The voltage will be lower and overall output will be higher for less power, and the current-drawn from the battery should be lower (because of the lower voltage).
If the driver uses constant voltage (I think the Fenix E01 uses it), then it will probably be overloaded by the new LED (but I don't think many people would put a XM-L2 in the E01, although I would really like to see it).

(DISCLAIMER: I am NOT responsible for broken lights modded based on my (unproven) presumptions, so correct me if you know I'm wrong).

Maybe the Constant Current starts with a to high voltage on turbo and failing before it can lower the voltage to get the required current, while the lower modes don't overshoot the max voltage. Although this doesn't explain why it still works for a few seconds, which should be more than enough to adjust the voltage.
Another possibility is that the turbo mode was always unregulated, just boosting the voltage as high as it would go from the battery voltage.
(But again: armchair expert)

If the voltage is too high would it not burn the driver out? It's odd to me that once it shuts off I can't turn it back on through the switch but instead have to unscrew the head some then screw it back on to turn it on. I've seen some others on here who have swapped out this light with a Nichia 219 emitter and XM-L emitters with success and nothing like I'm describing which is why I'm trying to figure out what's going on with it. I wish I could try a 14500 battery in it but I'm afraid I might burn out the driver.

I put a N219 with a very low-forward voltage in a D10 and it drives that emitter extremely hard compared to the XP-G that was in there before. The light is probably twice as bright and overheats in only a few minutes now. I have a feeling it's probably voltage-regulated and not current-regulated but I'm not 100% sure.

The XM-L2 has a really low forward voltage so if that's the case I wouldn't be surprised if your light was hitting thermal shutdown. Since the D10 has parasitic drain (the microcontroller never shuts off unless the battery is removed) once the over-temperature flag is set it might just stay on indefinitely.

calipsoii said:

I put a N219 with a very low-forward voltage in a D10 and it drives that emitter extremely hard compared to the XP-G that was in there before. The light is probably twice as bright and overheats in only a few minutes now. I have a feeling it's probably voltage-regulated and not current-regulated but I'm not 100% sure.

The XM-L2 has a really low forward voltage so if that's the case I wouldn't be surprised if your light was hitting thermal shutdown. Since the D10 has parasitic drain (the microcontroller never shuts off unless the battery is removed) once the over-temperature flag is set it might just stay on indefinitely.

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Hmm so does your light with the Nichia LED act similar to mine or does it shut off after a few minutes? What would be the difference between an emitter having a low forward voltage vs a high one? Also what is the difference between a voltage regulated and current regulated driver? Sorry for all the questions I'm new to the world of soldering, drivers and emitter swaps so this is all a little new to me!

snowlover91 said:

Hmm so does your light with the Nichia LED act similar to mine or does it shut off after a few minutes? What would be the difference between an emitter having a low forward voltage vs a high one? Also what is the difference between a voltage regulated and current regulated driver? Sorry for all the questions I'm new to the world of soldering, drivers and emitter swaps so this is all a little new to me!

Click to expand...

Mine gets hot but doesn't shut off. If it got any hotter I imagine it would shutdown due to heat. Removing the battery resets the light which is why that's working for you.

Let's say your light shipped with a Cree XP-G2 LED. Let's also say the driver is set to supply 3.2V to the LED (voltage regulated).


At 3.2V, the XP-G2 will run at ~1.5 amp.

Now let's say you swap the LED to an XM-L2 but the driver still outputs 3.2V.


2.3 amps! Now things are getting way too hot and the light shuts off.

Current regulation works the other way around - instead of supplying a set voltage it supplies a set current. The driver outputs 1.5A and adjusts automatically for new LED's and everything is cool.

Not saying that's what is happening here but your experiences and mine seem to indicate LED's with lower forward voltages are running hotter and brighter.

Thanks for that explanation it was very helpful and makes sense. I didn't realize the D10 lights had thermal shutdown built into them to prevent overheating. The light is much brighter now with much nicer tint, it was greenish before now it's a nice neutral/slightly warm tint and much brighter even at medium brightness. Thanks for the help everyone it's a relief knowing I did the emitter swap correctly it's my first one and first attempt at soldering!

One interesting thing I noticed when swapping the emitter on my D10 and then looking at my D11.2 emitter is the LED star was made of copper in the D11.2 and was extremely tiny, say 11-12mm while the D10 star was larger at 14mm and aluminum. I would estimate the brightness of my D10 at moonlight to now be in the 2-4 lumen range vs around .5 or 1 lumen before and the max brightness on AA probably around 160-180 lumens.

As an update to this thread I'm considering swapping the high cri XM-L2 emitter out for a different one since the light seems to be voltage regulated. The original LED was a Q2 or Q5 not sure which. What current high cri (70+ and warm) would be recommended that wouldn't push the driver too hard? I was thinking maybe an XP-G2 might be a good option, or a Nichia? Any suggestions or ideas? Thanks!