Yes, and it was a lot of try and error, some dead ends… and a lot of fun. Just like today, really. 
It’s just that in these years BLF as a whole has developed an incredible base of hardware and firmware. And it still moves on.
To me some weird historical baggage is how the E48 and E96 series don't include the E24. Sure you can get 2% spacing with fewer resistors by starting over, but then you still ALSO need the E24 resistor values on hand anyway(if you want to be stocked up), so it's actually more in the end. I suppose it makes sure nobody accidentally uses 10% resistors when 1% is needed. In practice it doesn't really work out that way since 1% tolerance E12/24 values still get used at least as often as not, probably because people don't have to look them up. How often do you see a 1% 47.5 specced? Probably almost as often as a 48.7, but not nearly as often as a 47.0.
Wow! What did I say in here that earned me a rude mark?
It certainly wasn't me.. or not unless I clicked something by accident (that could be possible). Anyway, we're cool as far as I know.
WHAT? 
:person_facepalming:
So about C1, it turns out it does want to be bigger, for the same reason many of the caps do, 4S, high voltage. I forgot that C1 is full voltage. In 0805 10uF ceramic or Ta, there are no x7R caps over 16V on digikey at least. Best I can do is a $0.57 cent 25V X7S ceramic. That should probably work for such a light load, on the other hand the cap is right next to the inductor pad. The 1206's are $0.20 in bulk, and basically one more is free if only making one driver anyway. So yeah, we can probably make due with an 0805, but ideally, it's specced as 1206.
I am not sure what all the rude clicking is about. The only one I have got was a post that everyone agreed was not rude. I just ignored it as someone having a bad day.
I will see what I can do when I rearrange things. I would not hold out high hopes though, it is really tight over there and DEL likes to see the traces as short as possible for all the MCU power leads.
Got the shopping cart almost done. This is going to be expensive. Heck it might be more fun designing it than buying it. ..yeah, looking like about $22 plus the board of course. Ouch.
Yeah, I kinda got that sense fairly early on. Glad to have it as an option but not real practical to actually use for most lights.
This is why I have been reconsidering making an op-amp driver. Not as efficient but a heck of a lot simpler, easier and cheaper.
I just have not had a lot of luck picking out an actual op-amp IC with which to start such a build.
Oh as for rude.. the button is right next to reply. I suspect that's the main cause. The op amp sounds good. It's the middle modes that are hard to get well with anything, and those are the modes I like.
Yeah, I figure the middle modes could be sorted out with a combo of pwm and resistance to keep heat under control for the higher powered setups.
In the grand scheme of things, spending $25 on a very advanced driver isn’t bad at all. Ok, so it’s not cheap, but what is these days and still holds value? So if we’re building a nice big light, it’s an essential qualifier for ultimate success. I don’t mind paying it, not every light would get a driver like this so it would remain a special build and would show the effort.
That’s one thing I’ve not understood fully… When the MCU is shut down, the OTC get’s discharged through the voltage divider? That means that the two separate pins are internally connected when the MCU is off?
I don’t understand it either but I have seen the effects first hand. Normal OTC calibration settings are in the high 100’s with the 19.1k but with the 22k resistor I had to bump it up to right at the limit of ~240 or so and it proved to be not as consistent in my testing. So I went back to 19.1k myself.
22k works fine, just more of a hassle to calibrate.
I’ve seen many report it so I don’t doubt it it all. I’d just like to understand why. Once I get home I’ll measure resistance over the pins on a MCU that isn’t connected to anything.
Please do report your findings. I never cared enough to actually figure out the reason why myself.
Sometimes when you think you understand something is when you haven't thought about it enough (referring to myself). I had missed a couple of details here at least.
Update: yeah, I was definitely confused. The rest of this is just silly, well except for the bit about the zener voltage sensing:
The zener situation is probably quite a bit different than the LDO situation. In either case though when ground is disconnected the mcu should continue to run powered by the cap(edit: I really was thinking about C1 here confusing it with OTC). The current draw on it is I guess 10x higher than the divider current so it runs fast until it reaches shutdown voltage in zener case or the ldo reaches its dropout limit in the ldo case. But this is fast compared to the divider RC anyway so doesn't contribute a significant lag. Obviously it impacts the t=0 cap voltage.
In the zener case I hadn't appreciated that the cap ) stays only at zener voltage (plus or minus the input diode vf) according to this diagram anyway:
In the LDO case it stays higher and for voltage monitoring while on that matters, but when turned off it still should drain down to a pretty similar level, but the voltage of the LDO should have a big impact on OTC timing I think, because it determines what voltage the cap is left at when it drops out. It seems this has to be higher for LDO than for zener so maybe there's some confusion comparing OTC when there's two different situations.
I assume the LDO and mcu shutdown with high resistance between vin/vcc and ground, but maybe that's different for the two cases also.
Now what I really don't get is the turn on. In either case if the mcu/ldo has enough voltage to turn back on, the cap must have already charged back up no? And always to the same level. So what's left to measure? It seems to me almost like a resistor is missing between the R5/R1 juncion and the cap (or between the cap and ground). Shouldn't the cap charging lag behind Vcc if the cap level is to be detectable? Maybe that would help with some of these "stability" issues? Obviously it works, and I'm still missing something. Still maybe it works for reasons that aren't well controlled? Or more likely it's just me.
As for price, yeah. we're talking $22 PLUS the board. What do these board run? $20 for three? Which is still $20 if you only need one. Still, yeah, the big brand lights are expensive too. Maybe folks will find ways to shave a few $. The first folks to try it better know they're taking a gamble though and just be in it "for science". I certainly make no guarantees on my part. You're lucky if this thing doesn't burn your house down.
Yeah, the boards will be about $15-20 depending on where you get them. Might get them a little cheaper from china.
So basically it will cost as much as the Q8 to upgrade the driver lol.
Hence why I am thinking about giving an op-amp a go after this one is done.