Led bulbs

[Grall]

Incandescents probably have a lag on the order of half a second or so, at least when the bulb is cold. That's actually a lot more than the reaction time of an attentive human being, but still probably a lot less than your average fast food-eating, texting, lipstick-applying, crotch-scratching, big gulp-sipping driver. Not an order of magnitude for sure, though.

 

[AlphaWolf]

there's no way in hell it takes an incandescent (or halogen) half a second to light up

 

[Mize]

there's no way in hell it takes an incandescent (or halogen) half a second to light up

Yeah, the CF bulb here on my desk (at room temp) lights up so fast I cannot perceive any delay. Can't imagine an incandescent or halogen would be slower.

 

[Grall]

Looking at a blinker signal on a car (where the light switches on and off a lot), there's a noticeable delay before the light reaches full brightness. If I am able to notice it, then the delay exists...

 

[AlphaWolf]

why are you using indicators as your example?

And I certainly don't see any delay (other than the actual switching from on off), perhaps you're seeing an actual fade in effect.

 

[Gubbi]

The lag from a tungsten incadescent light bulb is the time to warm up the filament until radiative cooling (light) kicks in.

Google says a typical tungsten filament weighs on the order of 15mg.

Typical temperature of the filament is between 2000 and 3300 K, or 1700-3000 C. Specific heat capacity for tungsten is 0.13J/g/K

For a 40W bulb this gives us a lag of 0.13*0.015*(1700 to 3000) / 40 ~= 80 to 145 ms

Fast, but perceptible.

Cheers

 

[Jawed]

I'm kinda shocked that none of you guys have ever noticed that a car fitted with incandescent brake lights on its rear corners and a LED high-level brake light shows quite clearly that the high-level brake light is seen earlier. This layout is still very common.

 

[Mize]

I'm kinda shocked that none of you guys have ever noticed that a car fitted with incandescent brake lights on its rear corners and a LED high-level brake light shows quite clearly that the high-level brake light is seen earlier. This layout is still very common.

Such cars exist?

 

[Mize]

On another note, if the typical reaction time for brake lights is 0.67 seconds (found that somewhere) and drivers remain 2 seconds behind cars (you all do that, right?) then either should work fine.

I realize most people in my rear view mirror (meaning most of you too) tailgate (tailgate being < 2 full seconds behind), but the point is no amount of safety will overcome poor driving.

If you make it idiot proof, they'll just build a better idiot.

(I'm all for LED tail lights btw)

 

[zed]

Such cars exist?

Aye? Theyve been commonplace on roads for maybe 2 decades
oddly couldnt quickly find a good picture but
you often see them (where the 626 is) so next time youre following watch them apply the brake (unless the ones in the corner are the same), the LED in the middle will light up a fraction of a second before the corner lights do.

from a pdf

Standard incandescent brake lamps have a relatively slow rise time. It takes
approximately a quarter of a second for them to reach 90% of asymptotic light output, causing
potential delays in responses by following drivers. The present study evaluated reaction times
to brake signals from standard incandescent brake lamps and from three alternative brake
lamps with substantially faster rise time: neon, LED, and fast incandescent. The study,
performed in a laboratory, simulated a daytime driving condition. The subject’s task was to
respond as quickly as possible to the onset of either of two brake lamps in the visual
periphery, while engaged in a central tracking task. Brake signals were presented at two levels
of luminous intensity.
The results showed that reaction times to the alternative brake lamps were faster than to
the standard incandescent lamp, with the advantage averaging 166 ms for the LED and neon
lamps, and 135 ms for the fast incandescent lamp. A reduction of the signals’ luminous
intensity from 42 cd to 5 cd increased the reaction time by 84 ms. For the neon, LED, and
fast incandescent lamps all at 5 cd, the frequencies of reaction times longer than 1 s were all
similar, and they were comparable to the frequency for the standard incandescent lamp at 42
cd.

http://deepblue.lib.umich.edu/bitstream/2027.42/64045/1/84696.pdf

 

[Grall]

High-level LED brake lights are very common today, because of the fast reaction time I suppose, but probably also for the shallow design depth LEDs allow; no parabolic reflector needed for the bulb, or room to mount the lamp socket. However, corner-mounted LED lights are a lot rarer, even Toyota Priuses don't offer full LED rear lights. That's quite disappointing.

It can't be just a matter of cost either, as long as you don't need high-intensity white LEDs then a bunch of them don't cost much at all. Bright red and yellow LEDs are cheap and plentiful since around two decades or so, I have to assume the slow adoption rate is just a conservative, lazy car industry.

 

[Mize]

I have to say, based on what people have posted here, using anything but LEDs for brake lights should be illegal.

 

[Grall]

Just for S&G's, here's a Cree prototype LED-powered 18,000 lumen self-contained, hand-held floodlight:

According to the info the guy in the vid states (~160lm/W), this thing would draw about 120W at full power. Since the vid was made about a year ago, the thing is now "in production" - IE, you may pre-order it for $2500...... Kek!

 

[Silent_Buddha]

Manufacturing quality for LED bulbs needs to go WAY up. I'm avoiding them like the plague not only since they aren't cost effective, but because from what I've seen they have a really horrible failure rate.

Out of 24 lights (different batches from different manufacturers) a friend of mine has had 8 of them die within a few months of purchase. And the light that they produce is still very harsh and unnatural which is why he's gone through 24 of them.

He's still trying to find a good bulb, both in build quality and light quality.

I'm actually more excited about the potential for OLED lighting. Maybe we'll get more natural and less harsh lighting from that. Probably just wishful thinking.

Regards,
SB

 

[Mize]

I have 10 LED bulbs in use. Two are outdoor floods, two are outdoor porch lights and the rest are in the house. I like them roughly a bazillion times better than the CFs I've been using for years. I have 7 incandescent bulbs that were in use when we bought the house in 2005 that *ARE STILL WORKING* while we've replaced every CF (all the rest of the bulbs in the house up until LEDs) multiple times. CFs are, IMHO, utter shit and I will never, ever, buy another. I'll take LED or incandescent over CF every single day.

 

[Grall]

Osram CFs are great IMO. They should be available in the states too I think. Slight warm-up time on the light I use above the PC, but nothing significant really. Even baseline light level is quite strong, unlike with some cheaper brands I've used in the past.

It's certainly not significant enough to go overboard and never ever want to buy any CF whatsoever...

(Funny, the computer geek in me keep thinking CF = Compact Flash...)

 

[Sxotty]

Why not call them CFL?

BTW mize what is breaking on your CFLs? It is likely the power converter which LEDs have as well, if so it won't help you much.

 

[Mize]

CF/CFL (do we have to call them incandescentL now?), whatever, my experience with them is that they're crap and multiple studies show the same.

Sxotty, if you're saying that the ballast for cfLs is the same as that for an LED, I doubt it. Fluorescent tubes require high voltage/low current. Diodes are low voltage.

Edit: actually the CFL ballast has to provide high voltage, low current, DC to initiate the tube and then low-voltage, high-current AC during run time. Diodes are always low-voltage DC. I would posit that the latter circuit is much more reliable than a traditional CFL ballast.

 

[Blazkowicz]

I run 25W incandescent on my fixtures (narrow screw size).
twin 25W bulbs do put out light you can live with, supplemented with lamps. meanwhile the bluish 1W LED one I had bought as an experiment (10 euros mind you) is relegated to the closet (NOT for lighting it) : not only it's a spot on a fixture pointing upwards, but the result is moon lighting.

I like LED as it feels indestructible, cold running. a child playing with the light switch wouldn't break it.
I have low income so I will only ever buy incandescent (dirt chip, buy cost measured in cents) or something that doesn't break.

I've noticed that bulb which is given as 100W-incandescent equivalent. it's interesting on all counts, it's high power, actually shaped like a bulb with LEDs spread around it, has a nice heatsink and it's cheap!

twice the price I paid for my (outdated in the store) 1W spot, but over 15x the power.
waiting out for LEDs will pay off soon.

are the "warm spectrum" ones not that good, though?

 

[Sxotty]

Mize you are right about the ballast probably, but I don't know what is actually breaking there.

For your information when we moved I replaced all the incandescents with CFLs and only had CFLs fail in one light fixture over the 5 years.

I rewired that light eventually b/c it was hooked to some sketchy wiring and the lights quit failing. Anyway anecdotal evidence is anecdotal, but I have had good luck. There seems to be a lot of quality difference between various CFLs.