Why is PWM so Undesirable?

I've been owning and handling LED lights since they've been available, however, I have never taken the time to study PWM.

I know that most could care less, but some are totally against it. Why?

this_is_nascar said:

I've been owning and handling LED lights since they've been available, however, I have never taken the time to study PWM.

I know that most could care less, but some are totally against it. Why?

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Same here as long as i cannot see it pulsing, or it give me a headache i don't really care, I don't shake it around the walls on an normal basis, that how you end up in a SJ

John.

The major problem is, there are a lot flashlights that have a too low PWM frequency. If the frequency is low enough you recognize the flickering.

In general PWM is not bad as long as the PWM frequency is high enough.

If you dim your LED with lowering the current you will have at low currents a tins shift (mostly to green). This is also not really nice a greenish beam.

WarriorOfLight said:

The major problem is, there are a lot flashlights that have a too low PWM frequency. If the frequency is low enough you recognize the flickering.

In general PWM is not bad as long as the PWM frequency is high enough.

If you dim your LED with lowering the current you will have at low currents a tins shift (mostly to green). This is also not really nice a greenish beam.

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Always best to read a few reviews before you buy so hopefully any nasty tint at low power will be noted, or buy from a retailer you can return for a refund or replacement.


John.

PWM increases eye strain. Some people may have even head aches for "unknown" reason. If a user deals with moving parts/machinery there is a risk of a strobe effect when a violently rotating part will look like static. And I have no idea how might react people suffering from epileptic seizures.

I don't care as long as I can't tell it with the naked eye. Just read up on PWM last night. Tested a couple of my lights but they are very high frequency. I can see it being a problem if you take pics or vids of the beam as from what I can tell it shows best through a camera.

OP, I believe you are asking the wrong question, and the exact opposite question that you should be asking. Allow me to rephrase...

Why is PWM so desireable?

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FTFY

And personally, I would like to know why, myself, why some defend it as though they can't live without it. Tint shift? At the expense of efficiency and the possibility of using a light source that can trigger a migraine in those susceptable?

I have a feeling the answer is none other than brand/model loyalty, such that if that brand/model that uses PWM, instead did not... no one would be complaining that the PWM was taken away.

For my own self-preservation, I won't be posting in this thread again, but I'll be monitoring in anticipation of a satisfactory answer, if intellectual honesty could somehow push out brand/model loyalty to get to the deeper truths.

For some it's undesirable because it affects their coordination in the rain or snow. Some see eye strain. Some get headaches. Some just don't like it because the crowd says they aint supposed to like it.

If it doesn't show up in my photos (when I don't want it to) or cause my world to look like a discoteque when I walk in the rain it don't bother me.
But.... I have noticed some updates of lights that used to use it no longer using it. So perhaps some engineers don't like it either.

bykfixer said:

...So perhaps some engineers don't like it either.

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Maybe some engineers don't like it, but I believe the perception of PWM being bad in-of-itself hurts sales, so the advertisement people are against it. And with advertising, it is primarily the sizzle, not the steak, that is important.

Trolling post removed. I know this is a sensitive subject, and this has the potential to be a short lived thread... Keep it on topic and not personal, folks.

That colony would not been have save on the sttng if the tractor emitter power was not pulsed to encrease it`s power so they could move that stella core fragment. :twothumbs

John.

Speaking as an engineer, I do appreciate the increase in efficiency that often occurs in current-controlled low modes. More specifically, I recall when the 1xAAA Fenix LD01 went from the (PWM) XR-E to the C-C XP-G; additional runtimes were achieved on the low level beyond what would have been achieved by merely changing the PWM duty cycle.

I actually EDC both versions at the same time, and do appreciate the add'l efficiencies of the low mode on the later version.

Another example is when the Solarforce multimode XP-G dropins first came out; their lower modes utilized PWM and were considerably less efficient than the constant-current Malkoff 'L' & 'LL's. And tint wasn't even any better with the PWM Solarforce, as Malkoff used better LED's.

Had one for a while in an inexpensive backup, but eventually just gave it away & upgraded to a Malkoff 'L'.

scout24 said:

Trolling post removed. I know this is a sensitive subject, and this has the potential to be a short lived thread... Keep it on topic and not personal, folks.

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If you feel this thread is going to quickly spiral into the crapper, go ahead and lock it down. As the OP, I'd have no problem with that.

Let's keep this one open - the start of a new week and all.

KITROBASKIN said:

Maybe some engineers don't like it, but I believe the perception of PWM being bad in-of-itself hurts sales, so the advertisement people are against it. And with advertising, it is primarily the sizzle, not the steak, that is important.

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Good point. Perhaps sales departments often dictate an engineers adgenda, with the boss somewhere in the background saying to both parties"sales are sliding downward, fix the problem"....

I usually don't like PWM. Still I have nothing against PWM as long it isn't easily noticeable, the stroboscopic effect is annoying.

I'm also in the camp of "At long as the frequency is high enough, I don't care about it". I've got no idea what my personal cutoff for PWM frequency is, but I never saw it in my HDS lights, McG lights, etc. until it was pointed out to me. Once it's noticeable, I find it distracting. Never had headaches, etc. but ymmv.

Kestrel said:

Speaking as an engineer, I do appreciate the increase in efficiency that often occurs in current-controlled low modes........

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Agree. I've always felt that current-controlled lights, if designed right will be more efficient than PWM lights. Part of the hobby for me is to measure efficiency with a data logging light meter. You can't really measure the output on a PWM light, because, depending on the instance that data is taken, the light output may be anywhere in a PWM duty cycle.

Part of the art of a well designed LED flashlight in my opinion is in the driver circuit and its efficiency. I always pass on PWM driven lights.

Unfortunately as I age I am more susceptible headaches and general discomfort with flashing lights in general. In my early flashlight days, I had a Rayovac Indestructible 2AA that I used outside in the rain. I could see the effect, but it didn't do it with my maglite and it took a look on here to find out what was going on. For me, there is no sacrifice in choosing a non-pwm light so its just like choosing neutral white over a cool white light option so I don't own any lights that have PWM just on the chance I might detect it in other situations.