Multi-LED lights would be very interesting, especially after hearing that the 25/45/85 have four usable PWM channels.
Regulated output (with no PWM or very limited PWM) from zero to 3.04A also sounds really nice, and brings the driver up to par with high-end brands. I’d still put the FET on a PWM-capable channel though, to allow it to vary its output instead of jumping directly from 3A to 6A+ with nothing between.
On the attiny13a, there is one PWM counter, and it can optionally have two outputs with two different stopping points. Or it can have a single counter with a configurable ceiling. So, it has a couple different modes:
One channel: Counts from 0 to N each cycle and uses a duty cycle from 0 to X where 0 <= X <= N. N defaults to 255. This provides both pulse width modulation and pulse frequency modulation; the latter can be useful for fine-tuning output between individual PWM levels, and is used by Ferrero_Rocher/Ramping_UI_table.c .
Two channels: Counts from 0 to 255 each cycle, with one channel stopping at X and the other channel stopping at Y. The two channels are basically independent except for sharing a clock. This is what the BLF A6 does.
… and both can be configured for either a sawtooth wave (fast PWM) or a triangle wave (phase-correct PWM).
It sounds like the 25/45/85 doubles this, though the second set of PWM channels appears to have a slightly different feature set.
Oh, I thought that used the 84, not 85. And I made the mistake (for months!) of believing wikipedia’s page comparing atmel chips, which appears to be wrong or at least a bit misleading. But the 25/45/85 data sheet confirms four PWM outputs, and the differences between them.
The design I had in mind for running OTC, VDV and Esw on the same pin won’t work. Giving it another go by adding a MCU supervisor that has a built in 150ms delay. Thinking of the ADM1818 (from Analog Devices) because the RST (output) is low untill voltage level has been above a certain voltage threshold for 150ms (turning on the light). Then after the 150ms delay the + is let through to the VDV and OTC. The 150ms delay should give me enough time to read the OTC before the + voltage reaches it.
I’m no electronics guy, I just found this component by searching for a small delaying component with about the right delay. So does anyone with some knowledge about this stuff have any input? Even if it might work, are there better choices out there around the same size or smaller?
Didn't know Dr Jones driver was 85 based - actually totally forgot bout it. Soo hard following his stuff - I always seem to have a broken link to his sites. Think it's mentioned here: https://budgetlightforum.com/t/-/23510.
Edit: If he reads what we go thru, he's probably sitting back laughing - he knows all this stuff: been there, done that... We are breaking ground in making it public I suppose. Others, maybe many others, have gone through all this already. Remember the polish driver? 25 based I think.
The wikipedia article is definitely mis-leading. It shows no difference in PWM support between the 13 and 25/45/85's... Wow.
You can use pin 1 as an I/O, even on the 13, but after you do that you can't reprogram it without an HVSP programmer. That's another reason I bought a Dragon.
The 25-20SSU is guaranteed to function down to 2.7V, the 25V-10SSU will run down to 1.8V. The only other difference (besides price) is CPU speed, but for flashlight usage this doesn’t matter. I’m guessing you’ll be fine with the 2.7V 20-SSU, but there is a slight possibility that unpredictable things might happen if your voltage happens to drop below that.
For my 85 projects I only go with the 85V for peace of mind, but I bought them from Farnell that have slightly weird prices. Buying only a few and the 85 is much cheaper, but buying 25 or more and the 85V is cheaper. So I bought 25 of the 85Vs… Cheaper and don’t have to worry about the voltage specs.
I got the 25V's too. I'm running them at 8 Mhz now (still faster than the 4.8 Mhz we used on the 13A's) , so the 20 Mhz capability is pretty useless - I believe 8 Mhz is the fastest you can do on the internal clock anyway.
The only reason to consider the 2.8V version is if you’re going to build a bunch of drivers for 6V LEDs (MT-G2, XHP70). Then you might be able to save a little on getting some. Other than that, go for the 1.8V for peace of mind.
Really, the attiny25-20ssu will probably be fine. Other atmel chips usually work a bit beyond their official spec, it’s just not guaranteed. When problems do occur from running outside spec, one chip may be fine and another seemingly identical chip is unreliable. So I think it’s best to, at least do any initial testing with the 25v.
Dam, just realized that I’ve ordered ATTiny25
Need to order some ATTiny25V going to have to wait for them to turn up. Now the long wait begins.
Anybody have any good places to get some?
Try them. Often atmel chips can run fine a bit outside of the official spec. Also you can set the clock speed to 4mhz. Slower speeds are recommended for lower voltage range use. I suspect attiny25 non-V will be no problem at 4mhz.
We are breaking ground in making it public I suppose. Others, maybe many others, have gone through all this already. Remember the polish driver? 25 based I think.
