PWM and Animals!

Hi All!

Animals - especially cats, are no so fussed about light (which is useful when searching for them! Rescue not hunting).

However I have never tried a light with PWM. If any one either has experience, or has [for example] a cat, can you see if your cat is scared by a normal light, then try one with PWM, if you got other animals thats great too...

The big question is - are animals (with their different* vision) affected more by PWM?

*I had almost wrote superior, then I realised their different is better described as different. Depending on the Animal, they have certain advantages, we have other.

A few anecdotes.

The domestic furballs that mooch off of me are no more interested in the PWM from my keychain Fenix LD01 than they are when it's going all out with no PWM. Whenever I encounter free-roaming cats outdoors, it's pretty much the same story - they're more interested in my presence and proximity than whatever light source I happen to have.

I have different experience with rabbits. They're apt to just stare at the oncoming steady light of my bicycle's BC30 then zig-zag in front of at the last moment, but if I strobe it with the "turbo" function they're much more motivated to clear out moving steadily away from the flashing light.

I haven't noticed any separate response from any of the various critters around here when it comes to cc/pwm lights. Strobing lights yes but pwm is to fast for them to care I think.

I strobed a wild rabbit that was standing on its hind legs looking at me. It fell over. It stood back up and I strobed it again and it fell over again. Probably a seizure.
As far as PWM it only effects me. I haven't noticed any odd behavior from animals.

prnguinpoo said:

The big question is - are animals (with their different* vision) affected more by PWM?

Click to expand...

No, my cat does not respond to my CC light, nor to my PWM light. But, Im in the process of eliminating PWM from my lights.

Why would you intentionally buy PWM anyway? Now that you know better, just dont do it. And, could you please be specific, what light are you considering, that has PWM, and why is that light the one you want?

for example, I want a High CRI light with NO Pwm, so I chose the L3 Illumination L08 single aaa with N219b. I think it is excellent and recommend it, or its larger siblings the L10 or L11

Maybe the advantage of PWM when chasing cats, is that it freezes them in mid flight, LOL

Lou Minescence said:

I strobed a wild rabbit that was standing on its hind legs looking at me. It fell over. It stood back up and I strobed it again and it fell over again. Probably a seizure.
As far as PWM it only effects me. I haven't noticed any odd behavior from animals.

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I should add that when I say "strobe" the BC30 on the bike, that means I pulse it as fast as I can manually - hitting perhaps 3Hz. This sends them off with purpose whereas with steady brightness they're apt to stare at it until I'm right on top of them then zig-zag randomly in front of me, not sure if they want to actually escape or see what being squashed in two by the front tire is like.

I have a BC30 also, and that "button" can be fun, but only if running in the lower modes, so that it can make a Big difference. - 1200-1800, not so much...

Thanks,
-Chuck

I don't have a cat, so I tried this experiment on my pet planaria. After I PWMed it with a cheap, no-name light, it keeps going to the shock side of its tee-maze, not the food side.

Lesson learned: Don't PWM anything that you don't intend to permanently neurologically damage.

richbuff said:

I don't have a cat, so I tried this experiment on my pet planaria.

After I PWMed it with a cheap, no-name light, it keeps going to the shock side of its tee-maze, not the food side.

Lesson learned: Don't PWM anything that you don't intend to permanently neurologically damage.

Click to expand...

Perhaps you should repeat the experiment with non-PWM light. I suspect the outcome will be similar.

jon_slider said:

Why would you intentionally buy PWM anyway? Now that you know better, just dont do it. And, could you please be specific, what light are you considering, that has PWM, and why is that light the one you want?

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One in the give away threads. Didnt want to take it if i could not use it, especially as we agree not to sell it. I want to make sure if im entering then i cam actually give it a good home where it will see use

richbuff said:

I don't have a cat, so I tried this experiment on my pet planaria. After I PWMed it with a cheap, no-name light, it keeps going to the shock side of its tee-maze, not the food side.

Lesson learned: Don't PWM anything that you don't intend to permanently neurologically damage.

Click to expand...

LOL! I do not believe you, but stop shining lights on the poor things, any light bothers them.. you made me laugh:

http://www.biologycorner.com/worksheets/articles/planarian.html
"If given a choice, the planarian will actively seek an area of the dish that is dark or has some kind of cover….
If you shine a flashlight on the planarian, it will attempt to move out of the light…
If there is not another planarian present, one can reproduce asexually through a process called transverse fission. The organism will pull itself in half and the tail portion will regenerate a new head, and the head portion will regenerate a new tail. This process can be replicated in the lab by using a razor blade or scalpel to cut the planarian in half. In a couple of weeks, you should have two planarian swimming around in your petri dish."

prnguinpoo said:

One in the give away threads.

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I do not know which make and model of a light are you talking about. PWM wont hurt you, but, there is a reason it is being given away, it has PWM.. we dont want no stinking PWM! Just say No. Friends dont give Friends PWM. Some of my best friends have PWM, because they are ignorant, LOL!

On a more serious note, if its a new Copper Maratac, I would take it, and change the driver out .
In fact, I have a new Copper Maratac, and I just paid Vinh to remove the PWM driver and replace it with a Current Controlled driver.

you might also want to read the PWM Sticky

jon_slider, I can appreciate your distaste for PWM (and all else equal, I prefer CC as well), but you should stop insisting that is has no benefits. It reduces or eliminates tint shift at lower drive levels. Furthermore, the real bogeyman is low frequency PWM, not PWM in general. If a light is flashing at 20KHz, you wouldn't be able to detect it anyway without the use of an oscilloscope.

The light in question is a Black Shadow Terminator. PWM has nothing at all to do with the giveaway.

A friend of mine is using a LED Lenser light which uses PWM(I am sensitive to flickr), and I have used that light for photographing frogs, toads and lizards. I didn't notice any difference in their behaviour when using a PWM controlled light compared to light that uses current control.

thedoc007 said:

The light in question is a Black Shadow Terminator. PWM has nothing at all to do with the giveaway.

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Thanks! I agree. The specs for that light based on this review Blackshadow-Terminator Review say it is NOT a PWM light anyway:
Circuit : Digital CC circuit

jon_slider said:

Thanks! I agree. The specs for that light based on this review Blackshadow-Terminator Review say it is NOT a PWM light anyway:
Circuit : Digital CC circuit

Click to expand...

Check again:

candle lamp said:

PWM

The Terminator uses PWM for its lower output. (i.e., there is a flickering at Low, Med, output detected by waving the light, but can't see it at High.) The frequency at Low doesn't seem high enough to not be noticeable to sensitive user in practical use.

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thedoc007 said:

jon_slider, I can appreciate your distaste for PWM (and all else equal, I prefer CC as well), but you should stop insisting that is has no benefits. It reduces or eliminates tint shift at lower drive levels. Furthermore, the real bogeyman is low frequency PWM, not PWM in general. If a light is flashing at 20KHz, you wouldn't be able to detect it anyway without the use of an oscilloscope.

Click to expand...

I can detect the PWM in my Fenix LD01 by spinning it rapidly on its swivel and perceive a rapid and dense series of discrete light points. I would guess it's hitting 4-5 rotations per second in that photo. There look to be about 50 visible flashes in the photo covering about half the circle. So my best SWAG for base frequency is 400-500 Hz. Unless I'm snapping the beam rapidly across a scene and am looking for the flicker, I've just not found it to be noticeable in actual use. If it were in the KHz range, it would likely not be detectable at all without instruments.

Manufacturers like PWM because it's far simpler to implement than multiple current levels. Build your constant-current driver configured for the maximum current then implement additional brightness levels by switching it on and off rapidly at varying duty levels.

The effects of constant-current dimming vs PWM dimming are pretty much a settled issue:

• Here's an abstract from a study in 2005: pay close attention to figure 1.
• Even modern LED's (XML-2, XHP70, 219A) suffer shifts in output relative to current: look at the "Relative Chromaticity vs. Current" charts for Cree, "Forward Current vs Chromacity Coordinate" for Nichia. I suspect that these shifts have tightened over the years, but they're still a factor.

idleprocess said:

The effects of constant-current dimming vs PWM dimming are pretty much a settled issue:

• Here's an abstract from a study in 2005: pay close attention to figure 1.

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Thank You!


note that the Figure 1 shows large variations for the RGB LED, BOTH with DC Current Control AND with PWM. I think RGB Led systems is where the belief that tint shift happens with lower current is most true.

otoh, note that even the PWM of the PC (Phosphor Coated White) Leds that are used in my flashlights are almost entirely within the MacAdams 4 step elipse.

the linked paper says:
"within a 4-step MacAdam ellipse, the criterion for unnoticeable color variation."

"Both dimming schemes provide small chromaticity shifts using the PC white LED system"

"The RGB mixed-color system suffered large chromaticity shifts, regardless of the dimming scheme used"

My interpretation of the above study is that PWM is not needed to maintain the tint of Phosphor Coated Leds at lower current levels.

jon_slider said:

My interpretation of the above study is that PWM is not needed to maintain the tint of Phosphor Coated Leds at lower current levels.

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I think it's a matter of what percent of the emitter's useful current range you're operating in as well as how steady the thermal situation is. If you're varying from 0.1% to 100% current in a small device without enough heatsinking to maintain a more consistent junction temperature then you're going to see much more variation than you will with something that's operating in a narrower current range with better heatsinking.

Anecdotally, I can say that the situation has improved considerably over the years with LED performance becoming more consistent. Past experience is less relevant with newer parts - tint shift just isn't what it used to be.

idleprocess said:

I think it's a matter of what percent of the emitter's useful current range you're operating in as well as how steady the thermal situation is.

Click to expand...

My single AAA L3 Illumination L08 is current controlled with N219B led.
I see no difference in tint between its 3 lumen and 120 lumen mode. That is a 2.5% low.

I also see no difference in tint between the 12 lumen low and the 162 lumen high of my non PWM Thrunite Titanium with XPL. That is a 1% low

Other than being cheaper to manufacture a PWM driver, an advantage for the producer, I see no advantage to the consumer.

I think the idea that PWM gives better color fidelity to our flashlights is just marketing, derived from a reference to indoor LED lighting, that use RGB led systems. My flashlights dont use RGB leds.

Not to derail the OP's question, I dont think the PWM in the light he is hoping to win in the GAW will have any difference in effect on animals than a non PWM light would.

Oh well, didnt win the giveaway any way, although this does answer the q for future giveways!

The conclusion: PWM doesnt affect animals

Good