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View Poll Results: How do you feel about PWM dimming?

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  • Like it

    30 23.44%
  • Hate it

    53 41.41%
  • I don't care either way

    34 26.56%
  • What is PWM dimming?

    11 8.59%
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Thread: Do you like PWM (pulse width modulation) controlled lights?

  1. #1

    Default Do you like PWM (pulse width modulation) controlled lights?

    Multiple output is a nice feature, but I'd prefer it the regulation was done before LED and I hate PWM.

    PWM is ok for incans and motors since they have an inertia to ride through, but when it's used on LEDs, the resulting light flickers worse than old school fluorescent lights (which operates at 100 or 120Hz, because line cycle consists of a negative and a positive cycle and the lamps light up on both waves). Sinewaves don't spend much time at zero unlike PWM pulses that spend all of non-on time at zero.

    As perceived by my eyes, flickering is even more noticeable at lower on-duration (duty cycle) even with a frequency around 150-400Hz, which seems to be a common range for many flashlights.

    The phosphor in fluorescent lamps have a longer persistence than LEDs, so the effect isn't too bad. Flickering is noticeably worse on LED powered Christmas lights and such. HIDs are not nearly as bad as LEDs either as the capsule burns orange hot from heat which provides some light even during zero crossing to cushion visible flickering

  2. #2
    Enlightened
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    My ITP C8 shifts between 6 and 190 Lumen and I can't notice any flickering. However, with most car rear lights it's much worse and really annoying. So my answer would be: "Like it, if it's done right".

  3. #3
    Flashaholic McAllan's Avatar
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    Yes it really depends.

    I have a DX light (MTE C3-1 in stainless steel) which uses a very high frequency PWM. It's great. Haven't got any possibility to measure the frequency but it's quite high like a couple of kHz or something like that.

    Then there's the opposite side with lights such as the "new" mini Mag Lite. It's without discussion too low in frequency. Some of my other DX lights are quite low too but hey I don't expect as much from them as I do from a big company like MagLite. Even for a Joe Average that PWM must the on the edge of unbearable - only reason not to complain/mention if would be if he didn't knew it could be done much better. No major technical change - just up the PWM frequency and it'd be very nice.

    And then there's the AA Fenixes which don't use PWM. It's great too but they change color quite a bit on the lower modes.
    So having a hard time to decide. Don't know if I love PWM or CC but I'm quite fine with either as long is it's properly implemented and not like some monkey brain made it.
    The annoyance of having bought something mediocre lasts much longer than the joy of having saved on quality....(!)

  4. #4
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    Ive never seen PMW with my naked eye. I have a couple of lights that reportedly have this (ITP a3, qmini 123) but I have yet to visually notice PMW. The only time I've seen it was in a YouTube review (by Patriot) where the camera catches the PMW.

    So at this point, ignorance is still bliss for me.

  5. #5

    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    I don't mind it really. For me it's noticeable on the Mini Maglite Multimode but not enough to bother me. However, faster is definitely better when it comes to PWM.

  6. #6
    *Flashaholic* Flying Turtle's Avatar
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    It doesn't really bother me much, either. Of all my more recent lights I seem to notice it most in the Maratac AAA. Must be a particularly low frequency.

    Geoff

  7. #7
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    I have a couple of torches where I can see it on the lower mode but it doesn't really bother me and I think it's quite an ingenious way of managing the power levels.

  8. #8

    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    Isn't PWM the most efficient?

    What other choices are there?

  9. #9
    Flashaholic UpChUcK's Avatar
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    Quote Originally Posted by mn_doggie View Post
    Isn't PWM the most efficient?

    What other choices are there?
    Current controlled. And CC is more efficient.

    I like PWM as long as the frequency is high enough to not notice the flicker in use. PWM does give a nice low low, which I love.

  10. #10
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    I guess some people can see it more easily than others.

    My ITP A3 is a really nice light but the PWM on medium and low is really annoying - a sort of 'school disco' strobe effect. Strangely, it seems much worse than the L0D even though the frequency is not any lower . . perhpas there are sharper edges on the square wave or something, but comparing the two side by side it is clearly worse.

    The really really annoying thing about all this is that it's so easily avoided just by using a higher frequency like on the Preon. As SC says, it's OK if done right.

  11. #11
    Flashaholic* Henk_Lu's Avatar
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    While I know what PWM is and that many people complain about some lights, I can't discern any flickering in normal use on the same lights.

    So, up to this point I don't care about it as for flickering. I have loights however, which tend to a greenish tint on low modes and this is supposed as well to come from PWM, while I'm not sure about that theory of course. I surely don't like that and IIRC, current-modulation tends to a blueish tint, which would be nicer.

    Complicated all that stuff!
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  12. #12

    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    Quote Originally Posted by UpChUcK View Post
    Current controlled. And CC is more efficient.

    I like PWM as long as the frequency is high enough to not notice the flicker in use. PWM does give a nice low low, which I love.

    Does current controll use linear type regulator? Is there some type of series current controlling device (like a bypass transistor in the old days of voltage/current regulators)?

    I guess I'm not familiar with the types of current controlling devices used in flashlights. I've worked with PWM a bit over the years.

    Just did a search. I see how the current control is done.
    Last edited by mn_doggie; 03-30-2010 at 08:32 AM. Reason: found the info

  13. #13
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    Quote Originally Posted by UpChUcK View Post
    Current controlled. And CC is more efficient.

    I like PWM as long as the frequency is high enough to not notice the flicker in use. PWM does give a nice low low, which I love.
    only half true. above 20-30mA drive current CC is more efficient FOR THE LED, but PWM is (typically) more efficient FOR THE CIRCUIT.

  14. #14
    Flashaholic* John_Galt's Avatar
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    I only dislike it when it is very noticeable.

    Noticeable PWM is probably why I don't use myQuark AA, or Princeton tec Fuel. PWM on the lower modews of both give me a headache...
    I love my HDS/Ra Clicky... My only wish would be a 5th(accessible thru a 2click press) mode, and a 2AA tube.

  15. #15

    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    On some lights that reportedly use it I don't notice it, but on the ones I do notice it bothers me a lot. It can be nausea inducing (literally) if you're using it up close for a lengthy amount of time. I'll continue to live with it if it provides low lows.
    the harder I work, the luckier I get.

  16. #16

    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    I never noticed it on my Quark MiNi.

  17. #17

    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    Quote Originally Posted by Ragiska View Post
    only half true. above 20-30mA drive current CC is more efficient FOR THE LED, but PWM is (typically) more efficient FOR THE CIRCUIT.

    By "FOR THE CIRCUIT" do you mean it is more efficient on the energy source or on component count?

  18. #18
    Flashaholic Zendude's Avatar
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    I like it as long as the freq. is high enough.

    One advantage is it minimizes tint shift from high to low. The trade off being less runtime(from what I've read).

  19. #19

    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    Has there been any tests or studies on the effects PWM has on the eyes and brain for both short and longterm? Also, is there any correlation between eye twitches, hypetertension, or other scientific based syndromes or diseases and noticeable or non-noticeable PWM? Or even more simply, has anyone ever had physical side effects from viewing a subject being lit with a light with PWM?

  20. #20
    Flashaholic Zendude's Avatar
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    Quote Originally Posted by John_Galt View Post
    I only dislike it when it is very noticeable.

    Noticeable PWM is probably why I don't use myQuark AA, or Princeton tec Fuel. PWM on the lower modews of both give me a headache...

    Did you mean the Quark mini AA? Regular Quarks are current controlled. You must really be sensitive to PWM as the frequency of the mini is very high.

  21. #21

    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    Slow PWM is annoying sometimes, especially when sweeping the light. Sometimes it bugs me on my maratac AAA (I think 200hz). It's cool to point it at a PC fan in the dark and watch it appear to move slowly because of the stroboscopic effect Fast PWM is fine, above a couple KHZ there is no way you can notice it.
    Last edited by wyager; 03-30-2010 at 10:01 AM.

  22. #22
    Flashaholic* psychbeat's Avatar
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    its not noticeable (to me) on my quark mini123 or
    my nailbender sst50. kinda noticeable on my brunton headalmp.
    if its fast I dont mind it at all and the lower the low the better.
    I like that the tint is consistent.
    I use my lights outdoors mostly -except to read so
    Im not nearly as picky over these things as many.

  23. #23

    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    I suspect that the REM speed of your own eyes determines whether you see the pulsing with PWM, which is why it is so irritating for some people. I typically don't see it unless I rapidly bounce my eyes with the light running, then it becomes evident. If you don't see it, try bouncing your eyes a bit with your light running. Just like with taste testing, where the number of taste buds on your tongue dictates how food tastes to you personally, the PWM effect won't be suitable for everyone. Now, where's that Tabasco sauce?

  24. #24
    Flashaholic* Cataract's Avatar
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    If all PWM was at a high enough frequency so I can't tell, I wouldn't really mind, but I especially hate it on car lights (like Volvos and Cadillacs). I found myself slowing down or passing like a madman because my eyes where getting dangerously tired from those stupid flickering lights. Whenever I spot one of those cars with PWM lights, I pray god to take them on a different road and for the builders to change their desing.
    Cataract, Shiny things specialist.
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  25. #25
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    Quote Originally Posted by mn_doggie View Post
    By "FOR THE CIRCUIT" do you mean it is more efficient on the energy source or on component count?
    both. PWM circuits have higher circuit efficiency (less losses), and are smaller zimplier cheaper circuits to manufacture.

    that is one reason all really small multi-mode lights are PWM, a CC circuit would simply take up too much space and make the light much larger.

  26. #26
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    I guess I am quite sensitive for PWM. Without intention I regularly notice the PWM on flashlights, even those with higher frequency. But the lower frequences are really annoying. The light in my collection with the most annoying PWM is Solarforce L2R, even when moving my finger slowly in front of the beam I see multiples of the finger. The frequency has to be only slightly higher than what is visible without movement.
    Anyone who knows what frequence is required for that?10-20Hz?


    Cataract:
    ...but I especially hate it on car lights (like Volvos and Cadillacs)...
    I early noticed that on the new Volvos. I have asked friends if they see it but some have not still noticed it, so I think this confirms that I am sensitive when it comes to notice PWM.

    Regards, Patric

  27. #27
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    Quote Originally Posted by Swedpat View Post
    I guess I am quite sensitive for PWM. Without intention I regularly notice the PWM on flashlights, even those with higher frequency. But the lower frequences are really annoying. The light in my collection with the most annoying PWM is Solarforce L2R, even when moving my finger slowly in front of the beam I see multiples of the finger. The frequency has to be only slightly higher than what is visible without movement.
    Anyone who knows what frequence is required for that?10-20Hz?
    .
    Under normal use , I don't see any of the strobe effects caused by PWM ... However , if I wave a ruler in front of my Solarforces on the medium and the low settings , I can see the effect ... Other than this , it doesn't affect my use of the Solarforces ... It would certainly be nice if all torch manufacturers using PWM , would ensure that the chosen frequency was higher than it is at the moment ... It can't be too dificult to increase the carrier frequency ... I have listened to the torches and cannot hear any "buzzing" which is sometimes associated with PWM torches.

    I am not certain what the persistance is for a LED , but ideally the frequency used for the PWM should equate to this ... This could mean a very high PWM frequency which no doubt would bring its own particular problems ... Does anyone have a list of the PWM frequencies used by the drop-in manufacturers ? ... Perhaps the manufacturers don't realise the problem exists.
    .

  28. #28
    Flashaholic* rayman's Avatar
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    I like it if it's not too low.

    rayman
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  29. #29
    Flashaholic* FrogmanM's Avatar
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    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    I guess it could be annoying, but the "black box" in my SunDrop 3S seems to get the job done.

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  30. #30

    Default Re: Do you like PWM (pulse width modulation) controlled lights?

    Quote Originally Posted by John_Galt View Post
    Noticeable PWM is probably why I don't use my Quark AA...
    The Quark AA doesn't use PWM, unless you mean the Quark MiNi.

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