Location: (469219) 2016 HO3 // I get way more privmsgs than I can respond to, so please ask in a public thread if possible, for a faster answer.
I often hear people suggest the shower test as a way to detect whether a light uses PWM or if it delivers constant current. The test is: Shine the light at fast-moving water, like a shower head. Then look for dotted lines. If it has dots or spots, it uses PWM. If the streaks are smooth, it’s constant current.
But I find the test unreliable and error-prone. So I took some pictures of how this test looks in real life, and I want to know if people can determine the correct answer.
Here’s the pic. The poll choices refer to this picture:
Both lights were running at 30 lm, and both pictures used the same camera settings. Clicking the picture provides a larger version.
If the only light source on rhe shower has PWM you should see it in all water beams, not just in some. So in both pictures the shower is illuminated with a non-PWM light source, or too fast to even notice this way.
I have trouble telling from that photo. I use a bicycle hanging in the garage; spin the front wheel and shine the light at the spokes. The bike is always there unless it is being ridden. If it’s being ridden I probably have little interest in checking PWM right then.
I think TK is playing a trick on us and one or both are not using PWM. I would normally say right and left is both PWM, but I think the trick is left is no PWM and right is PWM. Possibly no PWM at all.
…But I find the test unreliable and error-prone. …
It is.
I use the manual control on my camera/phone camera to check for any “flickering”, normally between 1/1000 to 1/2000 exposure the “flickering” will show clearly. I’m awfully sensitive to mid to low frequency “flickering”, even those that claims by some as “high-enough” or not PWM in its strict sense. For me, it doesn’t matter whether it’s On-Off or “Stay-On but does square wave”, as long as it’s not constant current, it’s being put to “flickering” category for me.
It’s like there’s 2 light sources. I get that the water droplets can move at different speeds which isn’t accurately represented with a still picture. But as pointed out by TK it seems like a pretty flawed test.
The dots in the second picture aren’t necessarily PWM, they just look like the “ripples” in a stream of water reflecting light at different angles to me.
all you have to do is wave your finger back and forth rapidly, in the beam
or point at a rotating ceiling fan
wle
—
"You never have the wind with you - it's either against you,or you're having a good day." Daniel Behrman, "The Man Who Loved Bicycles". It never gets easy, you just go faster. -Greg Lemond. ,ø¤º°`°º¤ø¸,ø¤º°`°º¤ø¸,ø¤º°`°º¤ø¸
all you have to do is wave your finger back and forth rapidly, in the beam
or point at a rotating ceiling fan
wle
There’s zero chance someone will be able to see 10kHz or faster PWM doing that.
maybe but
a. at that frequency, isn;t it imperceptible?
b. would the shower test work for that, assuming PCM/no PCM matters at that frequency?
—
"You never have the wind with you - it's either against you,or you're having a good day." Daniel Behrman, "The Man Who Loved Bicycles". It never gets easy, you just go faster. -Greg Lemond. ,ø¤º°`°º¤ø¸,ø¤º°`°º¤ø¸,ø¤º°`°º¤ø¸
firmware discussion thread
I often hear people suggest the shower test as a way to detect whether a light uses PWM or if it delivers constant current. The test is: Shine the light at fast-moving water, like a shower head. Then look for dotted lines. If it has dots or spots, it uses PWM. If the streaks are smooth, it’s constant current.
But I find the test unreliable and error-prone. So I took some pictures of how this test looks in real life, and I want to know if people can determine the correct answer.
Here’s the pic. The poll choices refer to this picture:
Both lights were running at 30 lm, and both pictures used the same camera settings. Clicking the picture provides a larger version.
Edit: The answer is here.
Neat! I voted CC for the left and PWM on the right.
Chris
I voted for both, as they have dotted lines that look very artificial to me.
did this a long time ago, like 1m below shower head its a lot better to see
with the right shutter speed you can even get very close to the PWM frequency with calculation of drops/shutter speed
[Reviews] Miboxer C4-12, C2-4k+6k, C2, C4 / Astrolux K1, MF01, MF02, S42, K01, TI3A / BLF Q8 / Kalrus G35, XT11GT / Nitefox UT20 / Niwalker BK-FA30S / Sofirn SF36, SP35 / Imalent DM21TW / Wuben I333 / Ravemen PR1200 / CL06 lantern / Xanes headlamp
[Mods] Skilhunt H03 short / Klarus XT11GT, XT12GTS / Zebralight SC50+ / Imalent DM21TW / colorful anodisation
[Sale]
Drivers: overview of sizes and types
DD+AMC based drivers Anduril or Bistro OTSM 12-24mm, S42, 24-30mm L6, Q8, MF01(S), MT03, TN42
Anduril or Bistro 8A buck driver for 20-30mm, MF01/02/04, TN40/42, Lumintop GT, MT09R
UVC and UVC+UVA drivers
programming key
Remote switch tail DD board with FET
Aux boards:
Emisar D1, D1S, D4, D4S, D18, Lumintop FW3A, Fireflies ROT66, Astrolux MF01, Tail boards like S2+
If the only light source on rhe shower has PWM you should see it in all water beams, not just in some. So in both pictures the shower is illuminated with a non-PWM light source, or too fast to even notice this way.
I guess..
Nice pic Lexel
link to djozz tests
I have trouble telling from that photo. I use a bicycle hanging in the garage; spin the front wheel and shine the light at the spokes. The bike is always there unless it is being ridden. If it’s being ridden I probably have little interest in checking PWM right then.
BLF Member Map, add yourself
My 8th Annual contest entry My 7th Annual contest entry My 6th Annual contest entry My 5th Annual contest entry My 4th Annual contest entry
My DBSAR inspired SRK lantern hand made mod
For the poll would “PWM” be any at all, or PWM at a frequency slow enough for a human eye to see it?
Any PWM at all.
But, specifically, the kind which pulses on and off. Not the kind which stays on but does a square wave oscillation between two different levels.
I voted left=constant, right=pwm. But I’m really unsure.
The Cycle of Goodness: “No one prospers without rendering benefit to others”
- The YKK Philosophy
Norman Bates would know.
“Electricity is really just organized lightning”
― George Carlin
I think TK is playing a trick on us and one or both are not using PWM. I would normally say right and left is both PWM, but I think the trick is left is no PWM and right is PWM. Possibly no PWM at all.
I can't tell. I'd use a control picture as reference, and compare, if this were my test.
To test for visible PWM, I use a fan. After that, I use a camera with very short exposure time
Streaks and dots in both pics to me
This…
It is.
I use the manual control on my camera/phone camera to check for any “flickering”, normally between 1/1000 to 1/2000 exposure the “flickering” will show clearly. I’m awfully sensitive to mid to low frequency “flickering”, even those that claims by some as “high-enough” or not PWM in its strict sense. For me, it doesn’t matter whether it’s On-Off or “Stay-On but does square wave”, as long as it’s not constant current, it’s being put to “flickering” category for me.
yup both have PWM but the right pic is worst
Nico -.-
…and what about the streaks?
It’s like there’s 2 light sources. I get that the water droplets can move at different speeds which isn’t accurately represented with a still picture. But as pointed out by TK it seems like a pretty flawed test.
oh I didnt see that
Nico -.-
I shine a light at my spinning usb fan to test for pwm. Works well
Is it just me, or is there a face in the water on the right side? Creepy!
There is a face there for sure.
Looks kinda like a caricature of Stan Laurel with his little hat.
Kind of a mirror-image of
Anyhoo, when I put my face close, stare at the image, and kinda go cross-eyed, I kinda see a 3D image of a swan.
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
The dots in the second picture aren’t necessarily PWM, they just look like the “ripples” in a stream of water reflecting light at different angles to me.
all you have to do is wave your finger back and forth rapidly, in the beam
or point at a rotating ceiling fan
wle
"You never have the wind with you - it's either against you, or you're having a good day."
Daniel Behrman, "The Man Who Loved Bicycles".
It never gets easy, you just go faster. -Greg Lemond.
,ø¤º°`°º¤ø¸,ø¤º°`°º¤ø¸,ø¤º°`°º¤ø¸
There’s zero chance someone will be able to see 10kHz or faster PWM doing that.
Fast movement of light source – the best PWM test.
WANTED Zebralights. My flashlights
maybe but
a. at that frequency, isn;t it imperceptible?
b. would the shower test work for that, assuming PCM/no PCM matters at that frequency?
"You never have the wind with you - it's either against you, or you're having a good day."
Daniel Behrman, "The Man Who Loved Bicycles".
It never gets easy, you just go faster. -Greg Lemond.
,ø¤º°`°º¤ø¸,ø¤º°`°º¤ø¸,ø¤º°`°º¤ø¸
Ha ha. It was a trick question. She’s not even using a flashlight.
“Electricity is really just organized lightning”
― George Carlin
She’s screwing with us… “PWM” are the initials of the person whose face is on the right side
Lol…..Selene is playing a game for sure…
I just read her response. Sounds like both are PWM however, just at different frequencies or types….
… (this space intentionally blank, to put the answer at the top of page 2 instead of the bottom of page 1) …
Pages