It looks pretty interesting. Any idea how it handles lower-voltage LEDs? Like, a red XP-E2 or XQ-E, for example, is down around 2V. I’m curious if it might be able to handle that or if it’d get too hot burning off so much extra voltage.
Voltage delta times current equals dissipated power. In this case it may be too much for a linear, though it depends on available cooling.
A buck converter is a lot better for low Vf emitters. Easy current output tuning and high efficiency. Used one a couple months ago for a friend's custom red XP-E2 SK98 build.
Can understand you may want to port your software, though. Porting to PIC or related microcontrollers found on available buck converters would help. Good luck in any case.
Cheers ^:)
The first few post and TK pretty well covered why there so popular but the history of the driver has alot to do with it to. These linear drivers came about in a completely different era than what we have now. Alot of batteries back then could hardly sustain 3 amps , especially the cheap fire brands. The top leds back then had a higher vf than now. Couple the higher vf leds with the tremendous voltage sag of most batteries back then and the linear driver was quite efficient in that era. It was the single best single cell driver out there. Easy to change the current by adding more 7135’s or unsoldering a few for less current. They were easy to mod and very very popular. As things progressed it’s hard to let go of what you know works good even if it’s outdated and starting to not be the best option. As it’s already been pointed out with today’s lower vf leds and the higher capable voltage of batteries under load it’s becoming not as efficient. But it’s still cheap, dependable, easy to find and highly moddable. Back when they came out they were the hottest thing since sliced bread. The very first one I remember looked like this.
It had no mcu for modes just on or off controlled by the switch. We use to master, slave two or more to achieve higher current’s, then the simpler 7135 piggy back method was born.
You have to keep in mind back when these came out, a led running at 1.5 amps was over driven. My memory’s a little foggy on this but I think it was the multi-die emitters that finally exceeded that. The SSC-P7 and the Cree MC-E, both had a high vf compared to today and the T6 xml was in there somewhere close.
Times change and their still very popular but I do feel its just a matter of time before the truth sets in and something better is developed.
I hope it comes from the good people right here on BLF. 
Thanks for the narrative, and well said! That’s why I welcome ideas such as what dsk3 brought up in the OP. Even if it’s not the exact idea that gets brought to life, it sparks good discussion and might get some wheels turning in many minds. 
Why would you want to know “it’s on it’s way out” when the battery is still 70% full…
Because that’s how it is most of the time.
There already are drivers which dim or blink when a certain voltage is reached as a warning, there is no need to have a constantly decreasing brightness over half or more of the usable runtime.
If you have an LED with a low enough Vf that it doesn’t decrease most of the time then you end up with low efficiency like 75% or worse, which is stupid. That could be another 30% longer runtime if you used a proper regulated driver.
Yes, it is. But I have a specific use in mind which is very small and needs four channels… and it wouldn’t have room for four separate buck converters. It also needs to be very resistant to impact, so I’d like to avoid any large components if possible.
I haven’t done too much testing yet, but Mike C has done a bit. He said their built-in temp regulation seems to do a good job of dialing down current automatically to keep things in check.
What can we do to support our developers?
Financially, there was a R&D fund that to my knowledge was never used to help driver developers. And really flopped - which may make people resistant to support another of its kind.
Is there some other way to help their budgets?
Is there non-financial support that we could provide?
Yeah, temperature throttling works pretty nicely, at least during my initial test, post #39: Driver giveaway: Constant current 17mm drivers, winners (finally) announced, post #2. - #39 by Mike_C
I had a fair amount of voltage to burn off, worked nicely and was very smooth. I’ve played with CAT4104s and they have temperature shutdown which is very annoying. They overheat rather quickly and then start a blinky party. Too bad really, they are rated up to 25V.
ToyKeeper, I’ll get around to responding to your post in my driver thread shortly. It was pretty heavy and I’m heading out the door. I’ll be back in a day or so!