Wow, thanks for taking the time to make this big writeup djozz. I think it’s full of great insight/perspective for those of us who “know this stuff”. I’ll probably re-read it a couple more times to really get it to sink in.
I couldn’t help but smile when I noticed that you didn’t mention the part # of the Zener, just the effort required to find it. For others it’s this info:
I can’t explain the behavior of the Zener build with the reverse voltage protection diode in place (it’s not supposed to work, but I’d have expected that configuration to damage the Zener pretty quickly). After placing the 220k resistor I expect that the Zener was unable to drop enough voltage “(current too low)”:What is a Zener Diode | REUK.co.uk and thus the MCU was fried due to the battery voltage.
EDIT: My personal advice would be to discard the MCU and the Zener used in that failed Zener mod and use new components for your next effort. The other components should be just fine.
i thought i for got something in my mouser kart :( CRCW0805200RFKEB,j guess i have to wait for my next order im not going to pay another $5 for shipping
Thanks for providing the zener link, should have done that :-)
Btw, I wrote the story to give a lttle insight in how these builds are for the 'less gifted' ;-) , but it by no means is a plea to do things different than how they are done now. I think all these developements are great!
Do not use Y5V instead of X5R. You may use X7R. Which capacitor are you having trouble finding? You should have no trouble with that.
At a glance, either FET looks acceptable to me. On the first page of this thread we talked a little about both FETs you linked to. (At the time I mentioned that PSMN1R2-25YL might not work well with Zener mods, but I don’t remember why. Maybe I was concerned about Qg. Anyway it’s probably fine, I wouldn’t worry about that.)
Thanks djozz for the build writeup,
The threshold to really know all the ins and out to know everything needed is very high, i am trying to assemble all the knowledge the last couple of months to get started with this driver building also, the problem is i have to learn about everything else needed about flashlights at the same time :weary:
Now i am probably making this more complicated than i really have to :-), but i started from 0 flashlights before October last year so this whole hobby is a lot to learn and comprehend to do all the fun mods you guys are doing.
What do you think of the PSMN1R5-25YL and SIR850DP-T1-GE3. Here i make a quick comparison, i included the PSMN3R0 / PSMN6R0 from previous page to compare it.
I can see that the PSMN1R5-25YL has a higher Gate Charge and Input Capacitance, is that bad? The SIR850DP-T1-GE3 has lower Gate Charge and Input Capacitance but higher Rds On (Max) @ Id and Vgs(th) (Max) @ Id.
I suspect that SiR850DP will not give the best performance for single-cell applications.
I’ve looked again at PSMN1R5-25YL. It still looks strong. The turn-on/off/etc delay is high, much higher than PSMN3R0-30YLD. This will probably affect the structure of your modes (I think that they may compress upwards? PWM frequency may need to be turned down? I dunno.)
I see no show-stoppers, I’d go with PSMN1R5-25YL if those were my choices.
Hmm, I did not notice the higher input capacitance. That’s probably related to the slow turn-on time. That could be a problem, but I don’t know. It might be OK.