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Car LED tail lights strobe rate too slow

J

joseph2k

Jan 1, 1970
0
Chris said:
I think it's a deliberate choice to make it like that. If they ran it at a
higher frequency, you wouldn't notice that the car has "New LED Taillights"
and the marketing value would be lost.

Chris

Could be, marketing shit heads will often do anything not yet illegal to get
their product noticed. Please note that such brightness variations have
been illegal for a long time for aircraft (yes the FAA & NTSB know
something that most of USDOT and FHWA do not).
 
S

Simoc

Jan 1, 1970
0
Don said:
No, I was talking about why digital displays were strobed rather than
having each LED die being fed steady DC. I made no mention of what
frequency to strobe them at.

I see, you just seemed to have referred to intentional "strobing" by
low freq to get "the secondary benefit" as you mentioned. And you also
explained that they worked at higher efficiency by doing so...or at
least people thought so.
Most digital displays are now LCD and I don't know how those work and
they may be multiplexed. In any case, LCD responds very slowly and I
suspect it will smooth out any multiplexing if multiplexing is used.

Yeps so you meant that the LED displays aren't used so much
anymore...that I did'n't think ;-)
Meanwhile, unlike the old digital displays, modern LEDs in tail/brake
lamps (used as brake lamps), traffic signals and flashlights will
generally have little or no or downright negative gain in efficiency if
they are pulsed with the same average current or the same average power at
which they are operated steadily. Many but not all taillights use PWM
because the efficiency of the red LEDs there will be either reduced or
unreliable (varying excessively from one production run to another) with
steady low current.

Yes - I knew that already, and I, too, disagree the idea claimed by
someone here, that the taillights would be intentionally visibly
strobed to gain more efficiency or visibility.

And for the OP's question, that has anyone other here noticed the too
low PWM freq, I am, too. I really have noticed that, although I don't
find it annoying at all, but I understand that someones may. And not
only annoying, it may be dangerous for epileptics etc. and I'm hoping
that it'll be corrected, too.
 
S

Simoc

Jan 1, 1970
0
Clive said:
Multiplexing flicker can sometimes increase dramatically in old
equipment due to the increased ESR of the PSU capacitors creating enough
ripple to cause a beat effect in conjunction with the multiplexing
frequency.

Ask if it's always flickered so strongly.

No need to ask - I saw myself when it was brand new :) Yes, it has
always flickered as strongly. And I also wouldn't think that caps would
dry so much within 5 years (although not impossible if those bad
chinese caps used in motherboards are used).
Then again, the older processors ran slower and multiplexing speed was
compromised by other processing tasks.

Hmm..that I didn't think. That made a sense, that higher mux freqencies
would be more popular today.
 
P

Paul Hovnanian P.E.

Jan 1, 1970
0
Michael A. Terrell said:
Like, "Back off, idiot"? ;-)

That's one possible message.

Many years ago, I had a Mazda RX-7. One option offered was an
illuminated logo mounted between the taillights. I had considered
replacing the stock panel with a scrolling LED panel. The default
display would be "RX 7" but with a selection of alternate messages I
could call up as needed.
 
D

Daniel J. Stern

Jan 1, 1970
0
Scott said:
I have seen a lot that were in the 15Hz to 20Hz range, including the
new Cadillacs.

And the new BMWs, absolutely-every one of them. And a great many of
the standard-format round and rectangular lamp units used on trucks and
buses (but NOT all of them! It's fairly common to see buses here in
Toronto with one taillamp exhibiting no visible strobing, and the
other, of a different but still major brand, exhibiting extreme
strobing as it scans across one's field of view.

DS
 
D

Daniel J. Stern

Jan 1, 1970
0
GregS said:
I just wished they would mandate being able to see both left and right front turn signals
on vehicles like they used to.

There was never any such a mandate. Turn signal angles-of-visibility
requirements have remained largely unchanged until a couple of years
ago, when an option was inserted into the regulations for manufacturers
to certify the front signals under regulations requiring *wider*
visibility angles than the old specs.
Putting them on the side mirrors in front, would solve that problem.

But, it would also create new ones if the signals at/near the plane
tangent to the front of the car were deleted.
When I see a stopped vehicle and don't see their turn signals, I don't give them any slack. To > me
they are there and don't know what their doing, but I have to still watch out

Your solution wouldn't help if they didn't use their signals...!
 
D

Daniel J. Stern

Jan 1, 1970
0
Pete said:
The flicker also attracts attention better.

I keep fairly close track of the international research in the field,
and I haven't seen any studies demonstrating that flicker of the type
under discussion, whether perceptible or not, contributes to the safety
performance of automotive lighting devices. Can you please provide some
references? I ask because this sounds like one of those marketeering
claims (compare "HID headlamps produce light that's closer to natural
sunlight!") with no basis in even theoretical human-factors science.
 
P

Paul Hovnanian P.E.

Jan 1, 1970
0
Daniel J. Stern said:
I keep fairly close track of the international research in the field,
and I haven't seen any studies demonstrating that flicker of the type
under discussion, whether perceptible or not, contributes to the safety
performance of automotive lighting devices. Can you please provide some
references? I ask because this sounds like one of those marketeering
claims (compare "HID headlamps produce light that's closer to natural
sunlight!") with no basis in even theoretical human-factors science.

I think this is a reference to peripheral vision's increased sensitivity
to movement. Google found this: http://www.eyetec.net/group3/M12S1.htm

I think the idea behind most of these products (flickering motorcycle
headlights, etc.) is to take advantage of this effect. I'm not sure how
much real science some of these manufacturers have done (selecting the
correct rate and duty cycle) to justify their claims.

The PWM frequency used to dim taillights seems to be too high to be
designed to take advantage of this effect. Also, a continuous flashing
wouldn't seem to be as effective, as the human brain tends to suppress
repetitive stimuli. The latest LED (and strobe) cop lights are going to
randomized flash patterns to overcome this.
 
D

Daniel J. Stern

Jan 1, 1970
0
I think this is a reference to peripheral vision's increased sensitivity
to movement.

I don't agree; movement ≠ flicker.
I think the idea behind most of these products (flickering motorcycle
headlights, etc.) is to take advantage of this effect. I'm not sure how
much real science some of these manufacturers have done (selecting the
correct rate and duty cycle) to justify their claims.

You're more charitable (or at least more diplomatic) than I am; I'll
come right out and say it: Most of this homebrew nonsense — flashing
CHMSLs, blinking amber "deceleration lights", motorcycle "headlamp
modulators" and the like — are all marketeering with zero science
behind them. Unfortunately, regulation of vehicular safety equipment in
North America is often more about politics (who shouts the loudest)
than about actual safety performance. So, we get public transit systems
installing "deceleration lights" on their buses without a shred of
evidence they help anything. We get the same motorcyclist foundations
that baselessly parrot stupidities like "Loud pipes save lives!"
lobbying for -- and getting -- permission to flash their headlamps with
"modulators" all day and all night. We get completely unregulated
aftermarketeers selling kits to make your car's CHMSL flash. All with
plenty of hype and commonsensical-sounding but thoroughly unscientific
babble about why each of these is the next great safety breakthrough.

DS
 
J

Jeff Jonas

Jan 1, 1970
0
I have rolled my eyes and looked at plenty of CRT monitors and TV sets,
and consistently see quite a lack of phosphor persistence - downright
dropping something like 90% well within a millisecond.

There are times that is desirable:
some devices use the CRT blinking to transmit data like morse code
to watches and teeny devices using just photo-sensors to receive the data.
They don't work with most LCD monitors: too slow, or not bright enough.
 
D

David Lesher

Jan 1, 1970
0
That's one possible message.
Many years ago, I had a Mazda RX-7. One option offered was an
illuminated logo mounted between the taillights. I had considered
replacing the stock panel with a scrolling LED panel. The default
display would be "RX 7" but with a selection of alternate messages I
could call up as needed.

Matt Helm had better decades ago; his T-bird convertible featured
across-the-board taillights with a mike -- he spoke, it scrolled.
 
T

TKM

Jan 1, 1970
0
David Lesher said:
That's one possible message.
Many years ago, I had a Mazda RX-7. One option offered was an
illuminated logo mounted between the taillights. I had considered
replacing the stock panel with a scrolling LED panel. The default
display would be "RX 7" but with a selection of alternate messages I
could call up as needed.

Matt Helm had better decades ago; his T-bird convertible featured
across-the-board taillights with a mike -- he spoke, it scrolled.

--
A host is a host from coast to [email protected]
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Have you've seen the system referred to in a post a while back? It's at:
http://www.leftlanenews.com/2006/03/25/forget-the-spinners-pimp-rims-go-hi-tech/#more-2150
The $12-20K price is a stopper though.

Terry McGowan
 
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