In for 2
In for 2
I did some testing on FW3A proto2 running at full power with a fresh 30Q cell, with the thermal ceiling set to 45 C. It was laying sideways on a table with a fan pointed at it. Here was its regulation pattern:
The main difference between options is whether that initial plateau exists. The light gets a bit hot to hold during that.
Although not shown here, beyond the right edge of this graph I put a few drops of water on the light, and it started getting brighter. Then I touched it with ice and it got brighter faster. So… it does step back up when the temperature drops; it’s just not shown on the graph.
Vickers, E., (2010)
The Loudness War: Background, Speculation and Recommendations
AES 129th Convention, San Francisco, CA, USA 2010 Nov 4-7 (Conference Proceedings - non periodical)
Serrà, J., Corral, Á., Boguñá, M., Haro, M., & Arcos, J.L. (2012).
Measuring the Evolution of Contemporary Western Popular Music.
Scientfic Reports, 2, Article 521.
Percino, G., Klimek, P., Thurner, S., (2014)
Instrumental Complexity of Music Genres and Why Simplicity Sells
PLoS ONE 9(12): e115255
Mauch, M., MacCallum R.M., Levy, M., Leroi, A.M. (2015).
The evolution of popular music: USA 1960-2010
Royal Society Open Science, DOI: 10.1098/rsos.150081.
Askin, N., Mauskapf, M. (2017)
What Makes Popular Culture Popular? Product Features and Optimal Differentiation in Music.
American Sociological Review, Vol: 82 issue: 5, page(s): 910-944.
I think the important thing is to remember these studies focus on ‘popular’ music ie what is marketable to the lowest common denominator in order to maximize sales.
I would always squeal with glee whenever another engineer would demolish the cherished subjective world view of the audiophile cognoscenti. Bob Carver remains a hero of mine.
That seems roughly equivalent to what Okcupid found when looking at people who try to make their profile appeal to a general audience instead of showing the things which make them unique. They end up with a lot of 3-star and 4-star ratings but virtually no 5-star ratings.
Whatever the 10% is which counts as “not crud”, I think at least most people can agree that pop music isn’t it. Being too generic makes it bland and mediocre.
As someone who grew up in the singer-songwriter era, it is especially shocking to me that the majority of popular songs over the past decade + have essentially come from two writers; Max Martin & Lukasz Gottwald (Dr Luke). There have always been prolific writers who sold songs to other artists, but I don’t think there has ever been an era when virtually all the top acts are little more than pretty facades.
Sigh…I’m going to go listen to some Alabama Shakes now to remind myself there are still amazing & unique talents out there.
Wow, I’m late on this one. I guess I have a lot of reading to do to catch up, but in the meantime, I’m in for one! This project sounds pretty hot, lol. :person_facepalming: :heart_eyes:
I sometimes put a light in a cool glass of water, where the cooling is usually sufficient to enable quite a lot higher output. I want the 1100>turbo range to have some sort of regulation in it, so that I can place the light in the water when it’s been running at the thermal limit and have it step up to the new equilibrium.
I’ll throw my voice in as someone who has a D4 and wants option A. I think the times I would use FET instead of the 7135 mode would be A) When I only want to use turbo for as long as possible before regulating down to whatever I can get and B) When I have enough cooling whether because it’s cold or wet enough to sustain more heat than the 7135 mode produces. Or if for whatever other reason it had more cooling than otherwise, or if I was less bothered by the heat or something.
This is the conundrum, fitting 3/4 of a Q8 into an S2 sized package.
“Ye cannae change the laws of physics”.
“I’ve got to have 30 minutes” …
Perhaps filling the head with a phase change material could keep it going on turbo for more than a minute before step down. Much much better than simply relying on thermal mass.
Quick estimate: Paraffin wax, heat of fusion 250 kJ/kg.
Find a way to fit say 25g, that could soak up 6.25 kJ, lets say on turbo its pulling 4A from 3.7V = 14.8 W ignoring the light coming out of the front.
So the wax could maintain the head at a safe level for 422 seconds = 7 minutes of full turbo before step down became necessary. Of course there would then have to be a lengthy cooling off period before giving it another full blast. Meanwhile it would make a nice handwarmer on cold days.
Another wacky idea: monitor the LED forward voltage shift with temperature to get a precise reading of the LED junction temperature rise. Saves the need for an MCPCB sensor and measures it where it really matters. Use high melting point solder too, in case of accidents.
PS: if there are going to be FW3Ti and FW3Cu in future, the thermal control may need some re-tuning to cope with the very different thermal properties in case A (particularly for Ti), hopefully the “universal” system will adapt when in 7135 mode.
PPS: I think there is still a place for “hotwires” in bright torches, at least the incandescent bulb chucks it’s waste heat out of the front instead of into an MCPCB, and of course the CRI is perfect Make a handy fire-starter in emergencies too.
Another vote for option B - safest option!
First off - thank you!
I’ll say I haven’t followed every minute of this behemoth thread, so pardon if this has already been discussed extensively…
My first thought is if we want the PID to function perfectly and be the sole method (over months and years of operation and thousands of samples!) keeping this thing from going to skin blistering temperatures is to have a dedicated thermal sensor as close to the (primary) heat source as possible. It’s very common practice now for bigger name manufacturers to have an NTC thermistor on the MCPCB. Measuring this far upstream will make it possible to get AHEAD of the temp control, and not require so much host calibration or predictive/preemptive throttling. One major concern I have with using the current temp sensor location, besides the obvious and previously stated shortcomings, is the driver retaining ring possibly coming loose on the F3WA. Most of you with a convoy tube light with right-hand-threaded tailswitch retaining rings has come across it loose over repeated use and battery changes. This could cause a serious change in thermal resistance in the sense circuit and potentially lead to extreme over temperature conditions. Small chance maybe, but one that’s avoidable IMO.
That said, if this can’t be done at this point in the project, then I really hope the safest and most reliable options are employed to limit the >1000 lumen modes. If timed step-down from turbo to high is necessary, that’s fine! Everyday carry is exactly what a light like this exists for, and no reasonable person would prefer burnt clothing and/or skin over an extra click to keep it in turbo if necessary.
Just for perspective, I remember the Eagle Eye X6 group buy, when we were hoping the light would be able to ACHIEVE 1000 lumens.
A MCPCB-mounted sensor would be awesome, but won’t be feasible on this light. Maybe in a later version, with a redesigned driver.
So for now the MCU is stuck making predictions based on a laggy and noisy built-in sensor.
Despite that though, the normal regulation works pretty well… except for the specific case of turbo, which it allows to run long enough to make the light uncomfortable to hold. But perhaps that could be avoided by adding a drop of thermal goo in production. That just makes the driver really hard to reflash. I hope future drivers will have programming pin access on the battery side of the driver, though the FW3A may not have room for that kind of thing.
The retaining ring doesn’t actually touch the body tube, so it’s far less likely to get loose over time. In the prototypes it does sometimes touch the inner tube though, which is a main factor holding up the project. Can’t go to production until that’s solved, because spurious button presses are bad. It’s easily fixed with a short strip of kapton tape around the end of the inner tube, but a better solution is needed.
Given how hot most of the electronics can run safely versus the low temperatures we’re expecting of them, and the fact that burns to clothing and such from lights like the d4 and this come from the intense light and not the body of the light itself, I don’t think that the non-muggle mode should be quite so cautious that being even a degree over the setpoint for a few moments would prompt a stepdown. I think it should just be allowed to get a bit uncomfortable for a few moments to allow you to see whatever it was you activated turbo to see, then let the thermal control figure itself out and lower it down into the sweetspot of the regulation range. And of course the potential of operating it in a cold or wet environment where the full turbo heat would be easily dissipated is a big point - if I used this as a handwarmer or in water to keep it cool.
In full turbo, and when approaching it, as the FET PWM ratio increases the 7135s contribute less and less to the current flow, so less heat is generated on the driver/MCU temp. sensor hence the increased lag.
A quick and dirty way to fix this might be to mount a power resistor as close as possible to the MCU, connected to the LED drive output. This way the parasitic loss in this heater resistor would provide the quick response needed for PID type strategies, compensating for the lower contribution from the 7135s.
If the driver was arranged so the resistor was only powered by the FET, not the 7135s, there would be no parasitic loss in 7135 modes, but that might require a second small FET just to drive it.
Edit:, or use a gate-able constant current source, shorted to ground, as the heater, rather than resistor+FET.
Otherwise the classic method is to use feed forward in addition to PID, but this requires a pretty good model of the overall behaviour and is not for the faint hearted.
Since we are not trying to thermally control it, simply to turn it down just before it overheats, I reckon some straightforward mapping of the behaviour could work.
Mapping could be attempted by taking a series of step response measurements using a thermocouple on the head and timing the duration from start temperature to critical temperature. Maybe map 8 or 16 different power levels, from full 7135 to full FET. These could then be used, factored by the head temperature measured at the MCU, to determine a step-down time for each power setting, the step down being either smoothed out, or left to step to give visual indication of what’s happening.
Once back down to full 7135 the universal algorithm taking over again.
PS: some more detail on how to use the LED Vf as it’s own temperature sensor:
PPS: You already have a constant current source on the driver (x1 7135) so if you could arrange a second set of wires to the LED (4 wire probe) feeding an ADC input to the MCU, you could do it, with just the tiniest flicker when taking the measurement. Guessing at 2mV/degreeC slope, you’d be looking to resolve say 200 mV over the range 0-100C, on the say 3V Vf, which sounds do-able.
How does Zebralight implement their thermal PID control? Because, it’s very response, doesn’t overshoot, and will quickly react both up and down to keep the light at the set thermal level. Granted, the brightest Zebralight is 2300 lumens, so not quite as bright as this light, but it’s still pretty powerful and needs to ramp down in a minute or so. It gets hot, but not too hot to hold.
My reference to “classroom theory” is because in this torch the temperature sensor is not closely coupled to the parts that are trying to be controlled. So it is a lot more difficult to do, and I am impressed by how well it works.
I regard what TK is doing as a pragmatic approach, using empirical methods, rather than a theoretical analysis.
Control engineering is quite a deep subject, I only studied it just enough to realise how little I understood.
to get an idea of some of the complexity.
No idea about Zebralights, but clearly they are doing something right. ISTR from posts here that DrJones has developed some impressive temperature control as well, but can’t find the details.
Edit: found DrJones’ work: H17F - programmable driver with full thermal regulation
PS: here is some less highbrow explanation, from the great Robert A. Pease, Applications Engineer for Nat. Semi back in the day, I’ve probably read every application note he ever wrote, required reading for any analogue engineer.
Oh man, that brings back memories. I used to subscribe to EDN just for Pease Porridge.