FW3A, a TLF/BLF EDC flashlight - SST-20 available, coupon codes public

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4149

You don’t need a diff-amp if you can sample both signals fast enough. But I’d suggest just clamping one to +V and sampling the switched signal, gets rid of the offset once you subtract cell voltage. It might be good enough. Of course sampled in-between regular operation, that’s why I suggested it could be done in a blink, in-between normal operation.

Just a mad idea though.

Edit: If this is doing without the voltage divider to measure Vbatt, as I suspect, then it could be a bit approximate, but measured Vbatt vs. LED Vf should still track if they are coming through the same pin to the same ADC.

One way to make that happen, put a large pullup fromVbatt onto the ADC pin. Measure Vbatt with everything else turned off (7135 and FET). Then pulse the LED with one 7135 for a few milliseconds, if necessary turning up the gain, measure, subtract, calculate, job done. All through one pin (possibly multiplexed with something else).

For best precision, take a slightly different two measurements, not Vbatt open circuit but Vbatt whilst driving the pulse (two pulses required)…

4150

I’m fairly new around here and have learned a lot from BLF. I’ve since picked up a BLF A6, an Astrolux C8 (thanks to WalkIntoTheLight’s review crushing the Convoy C8) and a Massdrop/Lumintop Brass Tool AAA.

As for PWM, I’ve heard it’s used in some cheap or budget lights as a way of cutting costs. I don’t know much about it. But I do find it annoying on an older light I have.

Would someone please clarify:

a.) why the FW3A will use PWM and

b.) if/how its use of PWM will have minimal noticeable effect?

Thank you!

4151

But you don’t find PWM annoying on the BLF-A6?

If you don’t mind PWM on the A6, you won’t mind it on the FW3A. They both use the same method, except the FW3A does it better. What people dislike is slow PWM, and that’s not what the FW3A does.

It’s about more than cost. A full current regulation circuit also requires more space and fancier heat sinking, and introduces a variety of other complications depending on how it’s done.

4152

Thanks for clarifying. You’re right… It’s the slow PWM I don’t like. I don’t notice it on the A6 and am pleased it will be even better on the FW3A.

4153

Most manufacturers now seem to be doing PWM the right way: fast. I still prefer current regulation, but you generally only get that on more expensive lights. I don’t find fast PWM annoying at all, it’s more for reasons of efficiency and well-regulated output that I prefer current regulation. For budget lights, it seems that a FET driver and PWM is the way they’re all done (for the high modes).

I think the FW3A shows more promise by using 8 (or is it 10?) 7135 chips. That should get much better regulated output on higher modes. Though, I still find the Convoys that use 8x7135 chips still suffer from dropping output as the battery voltage drops, well before I would have thought the voltage should start having an effect. It’s not as bad as pure FET, though.

4154

What else can you expect, when driving a typical white LED from a LiIon cell with a crude driver ?

The voltage mis-match is great. Huge inefficiency when the cell is full, and it barely works as the cell discharges below e.g. 3V (lots of energy still left there by the way)

The efficiency is all over the place (7135 and anything linear obviously better, until they drop out), the FETs run open-loop on crude PWM at the worst efficiency, with no voltage compensation AFAIK.

There are far better ways of doing this, but they cost a tiny bit more, and take skill to design.

Boost, Buck, Buck-Boost. Choose a good one and you might double your cell life compared with a crude driver. Makes all the debate about “what is the best cell” a bit moot.

It is long past the time when 7135/FET drivers should have any credibility, no-matter how easy they are to design and cheap to manufacture.

Passim.

4155

It won’t be feasible to change the MCPCB design again before production.

The inner tube issue is already solved, I think, but we’re waiting on test results to be sure.

Voodoo.

And probably more classroom theory than I’m using. When it oscillates, the oscillations are very regular, suggesting that it probably has a more formal design than what I’m using, or at least a much better signal-to-noise ratio on the sensor data. And probably more “I” with less “D”.

What I’m doing is a form of PID, but it’s less of a proper academic “Hogwarts/Brakebills” PID and more of a hedge witch “street” PID.

I have a H17F in a solid copper host with some serious thermal mass, and did some testing on its thermal response. This plot shows the H17F and an early version of Anduril from ~10 months ago. I found that DrJones’ method appeared to drop 1 PWM level every 0.5 seconds or so, until the FET was no longer active, then drop 1 PWM level every 2 seconds or so on the 7x7135 channel, until it was no longer overheating. It took about 8 minutes to stabilize, because the adjustment was very slow. Very smooth though, and it seemed okay in such a solid host. Bumps on its graph were where I accidentally moved the light while checking its surface temperature.

Meanwhile, Anduril stabilized in about a minute. These results are not directly comparable though, due to being in different hosts with different power levels. So at some point I should probably compare them in the same host to find out if the H17F can speed up when necessary.

On the FW3A, there was a spare pin so it actually has an “optic nerve” built in to be able to use the LED as a light sensor. But the way it’s designed probably wouldn’t work for temperature for a variety of reasons. Mostly, the reading is designed to auto-center on zero over time, so edges are visible but absolute levels are not.

The first prototype will likely soon become a dev host for optical sensor features. Those aren’t planned for release, but perhaps in a later version. Configuring a flashlight from a computer screen is a neat trick, but it’s mostly not very practical so I haven’t prioritized it.

4156

People sometimes complain about linear drivers, but for the most part they work fine as long as the emitters match the power source. The main benefit of a buck/boost is being able to run mismatched voltages, like XHP35 on a single cell.

Drivers could certainly be optimized more, but it seems like a matter of diminishing returns. Fancier drivers provide benefits most people won’t really notice, and sometimes the extra complexity comes with significant baggage. Sometimes it’s worth the trouble, sometimes not.

4157

On high or lower modes? The Convoy and similar drivers have an odd quirk that causes poor regulation on lower modes.

I built my first Convoy recently using an 8x7135 Qlite driver - pretty similar to the Convoy driver, but I have STAR firmware on mine. Out of curiosity, I tested the regulation with a linear power supply. Mine held regulation at ~3 Amps until the input level dropped below 3.4V when driving a 2.8-2.9V rated 219C. It dropped to 50% of initial current draw at 3.15V.

Considering Nichia’s datasheet shows the forward voltage is 3.4V at roughly that current level, this $5 driver seemed to have perfect regulation. There are caveats for voltage binning and the temperature dependence of Vf, but they don’t change the conclusion much.

Surprisingly, regulation was far worse on lower modes.

My 750 mA target (25%) mode fell out of regulation at 3.9V.
My 90 mA target (3%) mode was already out of regulation at 4.3V.

This wasn’t actually a surprise to me. I was looking for it specifically because when shopping for a driver, I noticed HKJ documented it over 4 years ago. He speculated based on oscilloscope data that the 7135 chips respond too slowly to the 16 kHz PWM to turn on fully when the duty cycle is low. Maukka measured similar when he did a more cursory output test of an S2+.

However, the D4 also uses a high frequency PWM for its 7135 chip, yet does not share this issue. I don’t know if it is due to the specific brand of 7135 used, a driver design issue, or if Toykeeper, TomE or others know a firmware trick to avoid it.

4158

Please add me to the list (2)

4159

All of the above. The FW3A uses a few methods to avoid that problem:

  • Chip brand: “Raptor claw” 7135 chip chosen specifically for its activation speed, so it will perform well with short pulses. The low-mode problems are mostly seen on “failboat” 7135 chips.
  • Driver design: 1x7135 chip on its own channel, so it uses the 350mA Vf instead of the 3A Vf, and can thus regulate longer.
  • Firmware: Slower PWM frequency at the lowest levels, like moon, to improve stability and reduce voltage sensitivity. Also reduces total power draw significantly, so moon runs about 3X longer than it would at full speed. (the D4 doesn’t do this, but the FW3A does)

So… regulation on this thing actually works pretty well.

4160

Aha! Thanks for the reply. I spent far too much time researching this issue before I gave up trying to find answers and bought parts for my build.

I should have just created an account here earlier to ask, instead of digging through countless old threads.

But I’m glad I mentioned it in this thread, because now I know the concern is already addressed in the FW3A.

Unfortunately, it seems there are a lot of drivers out there using the lower quality chips.

4161

All this from a $30-$36 light? Outrageous!
This thread, (well, portions of it) should be required reading for all flashlight manufacturers.

“Waddaya think, Joey? High, medium, low? Or low, medium, high?”
“Howzabout medium, low, high?”
“Brilliant! We’ve got our UI,… what else?”
“Wuddabout some flashy stuff?”
“Scope creep! We’re done!”
(end scene)

4162

Sign me up for 1, maybe 10 :slight_smile:

4163

I know what you mean! I’m leaning that way thinking of a couple extra for my kids.

4164

Forfive me if this has been asked before, does FW3A will have PID for thermal control? Thanks :slight_smile:

4165

ToyKeeper just said this a couple posts above.

So yes, it will increase brightness if the light is cooled down. I assume that’s what your are asking.

4166

Didn’t realize that post, mostly because i only took a quick glance of most posts here. :person_facepalming:
Anyway thank you.

4167

Please add me to the list for one (1).

Body color is not very important to me, but I think the silvery color of the prototype looks nice, even if not quite like bare aluminum.

4168

You probably don’t need to read every post, but ToyKeeper is one of the main FW3A team members who actually posts updares on this project. It’s always good to read her posts, even if the techno stuff goes over your head. Lol

FW3A Team
Fritz15: Design
Tommy TLF: General TLF communication
DEL: Driver
Tom E: Firmware (originally), driver
ToyKeeper: Firmware / UI, BLF gardening
The Miller: General BLF communication
pepinfaxera: Interest list management
MRsDNF: Early prototyping
Neal: Facilitating tasks in China
Lumintop: Manufacturing