List Lights that use NO PWM

[TheBelgian]

true, the PWM weasel clause applies to Zebras. They use Pulses that are not PWM by technical definition, since the Pulses do not drop to Zero.
However the fact Zebras do not use PWM does not mean they use Constant Current. In fact, Zebras do NOT use Constant Current.. clic pic for more info

I see there is some fluctuation of the output of the sc5fc, but it isn't pwm and more importantly, the fluctuations are said to be so low they can't be seen by eye. I don't know the absolute scale of the scope diagrams, but if say the light fluctuates between 100% and 90% that won't be noticable and has no notable impact on effeciency, so for all intents and purposes it has no PWM. Other lights like for instance the Fenix LD60 should be constant current but there the fluctuations are so great it does cause visible flickering which is as bad as having PWM.
This should be a list of lights with no visible flickering (although extreme high frequency PWM should still be counted as flickering)
<\2cents>

 

[TheBelgian]

Double post, crazy smartphone

 

[TheBelgian]

The scope traces you've shown are zoomed in on the fluctuations, on the absolute scope traces the fluctuations are in the 10% range, not perceptible.
Also, constant current circuits always have some noise. Perfectly flat constant current output is impossible (unless using linear regulators, with lower efficiency as downside), especially in small form factor lights like the Zebralight.
I'm not advertising for Zebralight, but I find excluding Zebralight for invisible output fluctuations (which many if not all constant current lights have) seems unfair.

 

[bykfixer]

None of the PKDL line up uses PWM.
Heck no step down for that matter.

Streamlight is getting away from PWM in 016 lights.

 

[jon_slider]

None of the PKDL line up uses PWM.
Streamlight is getting away from PWM

very helpful, thank you

on the absolute scope traces the fluctuations are in the 10% range, not perceptible.
...
I find excluding Zebralight for invisible output fluctuations (which many if not all constant current lights have) seems unfair.

I respect and appreciate the points you've raised.
I've added zebra to the list of lights with no PWM while we continue our discussion.

I don't own a zebra, if you do, could you please test: the beam close up, waving, and water drops tests listed below?

Suggested PWM/pulsed/ Non Constant Current Perceptibility tests that can be photographed:

1. it's visible on the scope as x% pulses
2. Lines visible in photographs of close up beam shots, or close ups of the led turned on.
3. Dots visible in photographs, while waving the light.
4. Dots visible in photos of shower water drops.

Additional areas of inquiry:
At what x% flux and at what frequency on scope traces, is there no photographic evidence from waving or water drop tests?

What is the %flux of zebralights and at what frequency.

List the %flux and oscilloscope measured frequency of some representative lights that use pulses that are visible in beam and led photos.

 

[TheBelgian]

I don't hhave a scope, but I'll try to do a photographic shower test next week.
An eyeball shower test doesn't show anything, but lets get some cold hard scientific objectivity. Next week.

 

[bykfixer]

Just aim it at a fan turned on and take pix of the fan...


With PWM


Without

 

[jon_slider]

for anyone interested in helping reconcile the pulses maukka showed, and the opposing view of selbuilt, below is some reference info to consider.. (these are why the Zebralight is on the lights with PWM list, with a disclaimer that it is controversial). note maukka has since posted that PWM was a bad choice of words, as the pulses dont drop to full zero, per the technical definition of PWM.. which is why IM now asking for the other photographic tests…. (besides the scopes)

I don't hhave a scope, but I'll try to do a photographic shower test next week.
An eyeball shower test doesn't show anything, but lets get some cold hard scientific objectivity. Next week.

thanks
the scope pics for SC5 are pretty much covered by maukka


====
maukka's review of the SC5
"PWM
PWM is used to control output on all modes except H1. The PWM is not visible to the eye, because of its low amplitude, but possibly shows up on camera. The cycling frequency is higher on higher output modes and ranges from 775 Hz to 5000 Hz. The amplitude however is higher on the higher modes."


maukka's SC5 scope readings http://imgur.com/a/IbSg6


====
selfbuilt's opinion on the SC5 (no scope shown)
http://www.candlepowerforums.com/vb/showthread.php?403440
"PWM/Strobe
As with my other Zebralight lights, I don't see any signs of pulse width modulation (PWM) on any the lower output modes. The light appears to be fully current controlled at all levels. "

 

[TheBelgian]

I don't have a SC5, only an SC52, so I can't do a straight apples to apples comparison. But I can still check for flicker.
I'll check all my lights (way to many) to see if I find non PWM flickering (I have no PWM lights)

 

[chillinn]

...it isn't pwm and more importantly, the fluctuations are said to be so low they can't be seen by eye...

All things being equal, you have 2 near identical Zebralights, one pulses like the stock version, but the other uses a legitimately constant current and true constant light output, no pulsing or PWM-like tricks. Battery life is identical, and because Zebralight is already a premium cost light, the retail price is identical. Which would you choose?

Herein lies the problem with the argument others have long made, saying, more or less, if you can't see PWM, then PWM doesn't matter. If I hid something in your living quarters that smelled like feces, but wasn't actually feces, somewhere you couldn't smell it, you won't mind? Not being able to detect PWM instantly with normal vision has no bearing on the evils of PWM. Sometimes, one only suspects PWM, and doesn't literally detect it, because after using a light for 2 hours a migraine sets in, or exhaustion. It is hard to predict that beforehand, and afterwards it's too late to do anything about it.

The argument seems to always be between one side that doesn't care, and the other side that does... but somehow, oddly, the side that doesn't care often ends up evangelizing, campaigning for, PWM, which is absurd, because they don't care.

PWM is bad, and so is anything even remotely like PWM, such as pulsing 10% dips in brightness on a frequency of 75kHz. There is nothing one can argue from the vantage point of "I don't care about PWM" to mitigate the evil of PWM.

And it's frustrating because it is not a "different strokes" kind of thing. You have a population that doesn't care their lights use PWM, or variable light output somehow or are unaware of it, and a minority population that ranges from prefer to not have PWM to can't tolerate PWM, and because the I-don't-care's are large enough to drive what is made and sold, the minority will be ignored by major manufacturers. But I bet most of the i-don't-care's or i-don-know's that are made aware of it, if offerred an identical light for an identical price without PWM, would choose the one without PWM. Wake up people! Don't be so complacent with "good enough," we deserve not just better... we deserve the best possible, and we are glad to pay a premium for it.

 

[Lexel]

So if you buy a DC psu, that has 2% ripple at 21kHz from switching is that not a DC power supply anymore?
or good old style PSU just AC 4 bridge rectifier with proper sized capacitor
I can plug in my DC stuff and it works, while it would smoke on AC

if a light gets a few % ripple and the only way to detect it is zooming in on my Oszilloscope why should that not be a CC light?

 

[chillinn]

So if you buy a DC psu, that has 2% ripple at 21kHz from switching is that not a DC power supply anymore?
or good old style PSU just AC 4 bridge rectifier with proper sized capacitor
I can plug in my DC stuff and it works, while it would smoke on AC

if a light gets a few % ripple and the only way to detect it is zooming in on my Oszilloscope why should that not be a CC light?

PWM, or switching, used elsewhere in the circuit where it is not affecting light output, where it is not an intentional scheme to trick the eye into thinking the light is constant, but is as constant as CC is, then that's not what we're complaining about.

Let's not confuse one PWM with another. jon_slider is pretty specific, but just saying 'PWM and the like' is apparently ambiguous to some. What I believe he is specifying with NO PWM is any engineered circuit intended to trick the eye into thinking the light output is a constant level when in fact it is flashing faster than the eye detects, whether to zero or 2%, whether for 200ms or Planck time.

idky the convesersation always ends up like this... https://www.youtube.com/watch?v=anwy2MPT5RE

I understand flashaholics have their favorite lights, and they are their favorite even if they use PWM, but taking the worst feature out of your favorite light shouldn't scale to all other lights, yet this is what has happnened. Because a favorite light has PWM, the PWM wars continue.

Would anyone anywhere ever complain if PWM simply vanished from the Earth never to return? Honestly, I have no idea what I'm trying to accomplish. Thanks jon_slider. Peace.

 

[vadimax]

So if you buy a DC psu, that has 2% ripple at 21kHz from switching is that not a DC power supply anymore?
or good old style PSU just AC 4 bridge rectifier with proper sized capacitor
I can plug in my DC stuff and it works, while it would smoke on AC

if a light gets a few % ripple and the only way to detect it is zooming in on my Oszilloscope why should that not be a CC light?

Imagine two bottles of water: one from deep drill mineral water source, another is sewerage recycling product. They look the same and have no smell. Which one would you drink?

PWM is poor engineering to make things as cheap in production as possible to get the most interest selling that crap. I prefer not to buy crap and sewerage recycling.

P.S.: Regarding "ripple" in supposed to be DC -- any inductive coil and the whole circuit becomes an EM emitter, making the whole system less energy effective and more noisy in radio band.

 

[Lexel]

Imagine two bottles of water: one from deep drill mineral water source, another is sewerage recycling product. They look the same and have no smell. Which one would you drink?

PWM is poor engineering to make things as cheap in production as possible to get the most interest selling that crap. I prefer not to buy crap and sewerage recycling.

P.S.: Regarding "ripple" in supposed to be DC -- any inductive coil and the whole circuit becomes an EM emitter, making the whole system less energy effective and more noisy in radio band.

there are enough drivers which use buck converters and CC to drive the flashlight
it is needed in all lights with single cell and XHP35, 50 and 70 LEDs
so we do also classify them now PWM lights as their voltage gets amplified by PWM and it is impossible to get a CC without ripple/HF noise out of it

while PWM is clearly definied to adjust output by switching On/Off!

 

[vadimax]

"Constant Current" is what everyone used to refer to "NO PWM" as, often abbreviating CC. While it sounds more ambiguous, it is deceivingly more accurate. Micro-electronics, I have figured out after decades of being in awe of even digital watches, can be pretty complex, and there even exist flashlights with circuits that use PWM and yet the brightness of the emitter is legitimately constant, actually without any PWM artifacts or pulsing schemes, visible or invisible, and it has nothing to do with frequency rates. I think also any incandescent that utilizes PWM is possibly a decent light source with a constant light output. I don't think this waters down the problematic issue that there are too many LED flashlights that use PWM the way we hate, and there is no way to know about it until you have already spent the money and used it, meaning, it's not exactly the kind of feature that ever makes feature lists used in marketing materials, unless it is the opposite, an affirmation of a constant current design.

So it can be a sticky subject with so many lights with so many things right with them losing a customer ultimately because of their lucky realization the designer/manufacturer/seller has a "what the customer doesn't know won't hurt them" underlying philosophy.

I am sorry, but you cannot compare LEDs and incandescent bulbs in regard to PWM. White-hot tungsten wire works as a stabilizing scheme -- it just physically unable to cool down during an "off" phase and thus effectively eliminates PWM in its emission. On the contrary LED is capable to pass on-off front instantly.

 

[eraursls1984]

I hate easily visible PWM, but overall its not that bad IMO. One thing no one seems to take into account is the bad tint shift from constant current lights. Maybe you guys only use max mode, but I use moonlight and low modes most often. Newer CC lights seem to be better, I'm not sure if it's the improved electronics or LED.

IMO, crappy low frequency PWM lights been to die. However , there is a place for high frequency PWM, constant current , and in between (Zebralight pulsing).

 

[jon_slider]

Gentlemen, thank you for the dialogue. Before this thread devolves into polarized perspectives on the pros and cons regarding PWM in flashlights, the merits of Chinese manufacturing priorities, etc, I would like to propose that we use some specific criteria to determine whether the circuit in any specific light has measurable effects.
----

Suggested PWM/pulsed/ Non Constant Current Perceptibility tests that can be photographed:

1. it's visible on the scope as x% pulses
2. Lines visible in photographs of close up beam shots, or close ups of the led turned on.
3. Dots visible in photographs, while waving the light.
4. Dots visible in photos of shower water drops.

----

Can someone who owns a Zebralight please provide the results of those 4 tests?

 

[TCY]

I emailed ZL about this and here's their reply:
Constant current regulators always use a feed back circuitry to measure the output current (that passes through the LED) and adjust the supplying power (up and down) to the LED accordingly. The action itself has (up and down) ripples. Good circuitry designs usually make the ripples so minuscule and/or fast enough, relative to the LED output, that they won't be seen by human eyes.
You'll need a digital camera with a global shutter (rather than a typical rolling shutter) or a traditional film camera to detect flashlight PWMs properly.

I did tests 2-4 and see no signs of flickering or PWM. If I get some time today I'll see if I can repeat this and upload the photos.

 

[jon_slider]

I found a photo of Zebralight that shows me it uses a type of Pulses that is not full PWM, but can be photographed.

As you can see in the photo below, in the sweep of the Zebralight, the dots blur together, almost completely, because the LED is getting brighter and dimmer, really quickly, but without turning all the way off. (I suspect this increases battery life)

Only the Malkoff in the photo uses true PWM, note that the dots have dark spaces between them, while the "circuit noise" lights have blurry light between the dots pictured.

My opinion: Zebralight and Eagletac, to me, are not techically Constant Current lights, but technically they also are not PWM. For me the bottom line is that both lights have dots that can be photographed.

Since we are splitting hairs, I think this old photo (a time exposure sweep) is a pretty good visual representation of the progression from "oscillation noise" to true PWM. L to R: SC52, Quark AA, D25A and MDC AA. I swept them all together, and fast as I can possibly swing my arms. Focus on the very bottom of the beam swipes.

IMHO: the SC52 and Quark show oscillation noise, and are undetectable with the naked eye (which I consider myself pretty good at), and an HDS will look similar, but this is not PWM. By my definition, the D25A crosses the line of true PWM (on ~3 modes) but I really need to concentrate to see this one (and it's one of my favorite lights, own a half dozen).... it is the fastest PWM frequency I've seen/photographed. The MDC AA is kinda slow, and it see it annoyingly frequently.


But if you don't know how or what to look for, my advice is - do not learn!

I am listing the "controversial" lights, such as Zebralight, on both the lights with PWM and the lights with NoPWM threads, with explanations.

 

[jto]

I happen to have an interest in the PWM characteristics because video cameras yadda yadda, I really want temporally smooth light (and high CRI). Asked Zebralight directly, and they were quick to respond:

None of our flashlights or headlamps in production now uses PWM (or any other type of pulsing mechanisms) in controlling different brightness levels. That said, constant current brightness control, being a control system, will have circuit noise or ripple no matter how small it is. But I don't think you'll be able to see any of these (relatively) small amplitude noise in still photos taken by a digital camera with either a global or rolling shutter. Not sure about the video though, especially if the scene involves fast moving objects with a dark background and a rolling shutter camera.There is no need for ND filters for shifting to particular brightness because all levels are controlled by the same (constant current) circuitry.

It should be noted that this may apply only to the H600/SC600 series or newer, as those what was I told I was interested in. Seems to be in line with the picture in the above post, "minimal ripple" seems more accurate description than any kind of "pulse".