# LED vs. Incandescent tail lights



## NewBie

I've known that LEDs are faster to come up to brightness than Incandescent bulbs, but didn't realize how much different they really were. Looking over a bunch of video, frame by frame (easiest method at hand right now), I see about 0.2 seconds faster, and really 0.3 seconds faster for the LEDs to hit full brightness. The circuit used on the LEDs takes 0.0002 seconds to hit full brightness, from when the brake pedal is touched.

So, lets say it takes 0.2 seconds. Assume you are driving 60 mph on the highway. There are 5,280 feet in a mile. 60 mph * 5,280 ft = 316,800 feet per hour.

There are 60 minutes in an hour, 316,800 feet per hour / 60 minutes = 5,280 feet per minute.

There are 60 seconds in a minute. 5280/60 = 88 feet per second.

88 * 0.2 seconds = 17.6 feet

So, an LED brake light could allow a person to <font color="red">*stop 17.6 feet sooner*</font> than with Incandescent.

But there is more. I've noticed that folks react alot quicker to the instant on effect of an LED vs. the slow ramp up in brightness of an incandescent. What this equates to in reaction time is unknown to me.

Here is a compressed video, sorry about the loss of frames and poor quality due to the compression, notice how the LED light, the top 3rd tail light comes on faster than the lower two normal incandescent tail lights:

http://www.molalla.net/~leeper/dougta~6.avi

(I had to watch the video about 20 times to get my mind and eyes sync'd to actually appreaciate it)


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## PhotonWrangler

Wow, thanks for doing the math!

Yes, the LED's ramp-up is virtually instantenous, which is why they can use them in communications as well as video screens. It's possible to modulate the light REALLY fast. /ubbthreads/images/graemlins/smile.gif

I've noticed that the on/off transition of LED tail-lights and traffic signals is much crisper looking and thus more attention-getting, which is definitely beneficial in terms of reaction time on the roads. The highly monochromatic nature of LED light is also more noticeable against a background of visual clutter. At least until all of the other lighted "clutter" is changed to LEDs also!


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## MaxaBaker

I've have read that the tail lights on the Maybach 57 (car) consist of something like 500 led's. I would NOT want to stop behind one of those /ubbthreads/images/graemlins/duh2.gif.

Wow. 17.6 feet could definitely save some lives.


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## ACMarina

The problem with them right now seems to be a lack of good aftermarket bulb replacements for cars that originally had incandescents. My car not only severely limits the light output from LED replacements, it also makes the lighting control module think there's a bulb burned out because of the difference in resistance from LED to bulb. It's a fast changing market, though, and I'd expect some good LED replacements soon. .


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## PhotonWrangler

[ QUOTE ]
*ACMarina said:*
My car not only severely limits the light output from LED replacements, it also makes the lighting control module think there's a bulb burned out because of the difference in resistance from LED to bulb. 

[/ QUOTE ]

I ran into the same thing. Replace the bimetal-strip-based flasher module with an electronic one and that'll take care of it. The electronic ones are direct plug-in replacements and look the same from the outside, so they use the same mounting.


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## ACMarina

That's where I run into the problem. My buddy and I put LEDs in his Tahoe, and everything went okay after we replaced the flasher module with a no-load flasher, kinda like you'd use on a semi or something.

My car has no flasher module. It's controlled by a huge black box of gadgetry and doodads, and while someone with a ton of skill could bypass the bod to make it use a different flasher, that someone isn't me by a long shot. The only option would be to wire in a resistor, I guess. .


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## James S

problem is that it won't save any lives because people learn to adjust to anything /ubbthreads/images/graemlins/wink.gif Take anti-lock brakes for example, initially they did reduce fender benders, but over time people learned that they could tailgate closer at higher speed cause their cars would stop anyway and as far as I know they have completely negated the safety gains. Same thing will happen for brake lights, they will learn that they can ignore your brake lights for an extra half second or so and then when they are too close or you are stopping they will still plow into you.

for myself, I really like led brake lights. I don't like the PWM dimmed ones though,, I find them to be distracting as I look around and they leave the trail of flashes. There are some cars that are obviously current limited that really do look very nice.


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## PhotonWrangler

[ QUOTE ]
*James S said:*
for myself, I really like led brake lights. I don't like the PWM dimmed ones though,, I find them to be distracting as I look around and they leave the trail of flashes. There are some cars that are obviously current limited that really do look very nice. 

[/ QUOTE ]

I've noticed that also and it is very distracting. It's so easy to spot an LED array that's being multiplexed or driven with PWM.


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## MaxaBaker

[ QUOTE ]
*James S said:*
problem is that it won't save any lives because people learn to adjust to anything /ubbthreads/images/graemlins/wink.gif Take anti-lock brakes for example, initially they did reduce fender benders, but over time people learned that they could tailgate closer at higher speed cause their cars would stop anyway and as far as I know they have completely negated the safety gains. Same thing will happen for brake lights, they will learn that they can ignore your brake lights for an extra half second or so and then when they are too close or you are stopping they will still plow into you. 

[/ QUOTE ]


But if no one else knows about it.......

Then again, the d*** media will make the story public and what you have stated above will come true.

Don't ya just hate how they do that: "Marines in Baghdad know where Saddam is hiding and are planning a secret attack..... but we can tell you this because it is impossible for them to be watching this newscast on a portable TV in a cave." <-- sarcasm

^not a real quote.(just so I don't get anyone pissed.)

Sorry to change the topic.


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## Justintoxicated

[ QUOTE ]
*James S said:*
problem is that it won't save any lives because people learn to adjust to anything /ubbthreads/images/graemlins/wink.gif Take anti-lock brakes for example, initially they did reduce fender benders, but over time people learned that they could tailgate closer at higher speed cause their cars would stop anyway and as far as I know they have completely negated the safety gains. Same thing will happen for brake lights, they will learn that they can ignore your brake lights for an extra half second or so and then when they are too close or you are stopping they will still plow into you.

for myself, I really like led brake lights. I don't like the PWM dimmed ones though,, I find them to be distracting as I look around and they leave the trail of flashes. There are some cars that are obviously current limited that really do look very nice. 

[/ QUOTE ]

I was goign to say, if people would just stay off my @$$ then I would not need LED brake lights lol. I was actualy going to put some on my trailer but someone told me they would be way to bright. People really get on my *** when I am pulling my trailer because they know they can stop faster than me. I don't even have Anti-Lock Brakes! Hell I don't even have disc brakes all around I have drum brakes in the rear! So I think it might be a good thing to blind them a little when they get to close, that would surely teach them a lesson. Or maybe I could wire up a middle finger in an LED array to take care of two things at once /ubbthreads/images/graemlins/smile.gif

IMO the best thing about LED tail lights is that they never burn out well, ok they might have burned out on my truck by now! But they arent going to to just go out like an Incan, which helps to avoid tickets.


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## NewBie

Well, it's probably not legal, but you could add a third tail light, and aim it down. That way they don't get blasted unless they are too close...

In my tailight, I am utilizing 6 1W LEDs and a fast current regulator. I was going to use some faster parts, but got to thinking, and 1/100,000 second time for comming up to full current regulated brightness is plenty fast enough.


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## Justintoxicated

why 6 1 watters?
In my experience 2 is MUCH brighter than a stock taillight?


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## NewBie

Depends on the designed flood/beam angle, and the size of the reflector. This one had an 18W incandescent in it.


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## Darell

You got pictures of that 6-banger, Newb? I'm curious how you're sinking the heat, and how much room you have. I've been building LED third brake lights for a while now, and I'm still not happy with the design. I REALLY wanted a Lux5 in red, but that just didn't happen, officially.


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## IsaacHayes

I have a lot of leds on my spoiler, and that comes on a lot faster than my regualar lights so that does help. My stock brake lights are behind smoked black lenses (they are like that from the factory) so I'm sure that cuts down on brightness. I do have a total of 4 bulbs in them though. Good incase one burns out on one side, there is still one bulb glowing..

The narrow angle of the LED 3rd brake light in my spoiler is pretty cool to see road signs way behind me on the high way light up at night!!


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## Paul_in_Maryland

[ QUOTE ]
*Justintoxicated said:*
[ QUOTE ]
*James S said:*
So I think it might be a good thing to blind them a little when they get to close, that would surely teach them a lesson. Or maybe I could wire up a middle finger in an LED array to take care of two things at once /ubbthreads/images/graemlins/smile.gif


[/ QUOTE ]Feel free to join me in being reviled in the thread, Blinding an aggressive driver?


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## DUQ

I'll be converting my car to LED's this fall. Brake, indicator,running and reverse lights. Everything. To correct any probs, you may need to add a load equaliser. If the correct amperage isnt being drawn, then the computer thinks theres a light out. Here's a link.

http://autolumination.com/equalizers.htm


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## bfg9000

The main problem with aftermarket replacement LED socketed bulbs is they are all just too dim behind a colored lens. A standard 1157 brakelight draws 2.1 amps at 14.4v which is over 30 watts. You'd need a LOT of cheap LEDs to equal that, which is the strategy taken by the car manufacturers with hundreds of LEDs.

For a retrofit it may be a good idea to add the LEDs rather than replace the stock bulbs with them. No load sensing problems and the two-stage brakelights would draw more attention, too. It's not like you will ever be replacing them so a drill and some glue would do the trick.


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## jtice

your vid explains it well Jar,

I agree, the LEDs are ALOT faster, and you are correct, the INSTANT on of LEDs catches your attention alot better than the rampup incans have.

I am seeing alot of emergancy, rigs, garbage trucks, etc using LED lights
and I dont think its just cuz they dont burn out.
I think they realize, or have been told that they are much faster.


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## hotbeam

Very noticeable turn-on time. Thanks for the vid Jar


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## Neuralgia

Actually, I just bought a scooter, and started a thread about some changes I want to make on my light system.
http://candlepowerforums.com/vb/showthread.php?t=92412

1st because I've read so much about car drivers NOT realizing you're coming and they turn left and WHAM. If you're concerned about safety, you can imagine how bike drivers are about it.

The other reason is because of the LED's "coming up" much faster, and breaking is something very important.

My scoot comes with H4 18w/18w (low/high) HeadLights, and I'm pretty sure those aren't good enough for my needs (planning to get H4 halogen 35w/35w)

Just like Intoxicated, but for a different reason I'm tryng LED's on my tail lights (both to prevent an accident, but in my case to save my life  )


The thing is, that for the turnlights you'll need a equalizer as DUQ said. (great link BTW). I saw this one: http://www.customdynamics.com/loadequalizer.htm#Universal Turn Signal



I've even heard you can use a "flasher" instead, but since I'm new in all this LED and candle world, I'm not sure which one should i get.
http://www.customdynamics.com/trick_flasher.htm

Any suggestions?



I found this site www.superbrightleds.com. They have the lowest prices I've found online http://www.superbrightleds.com/cgi-bin/store/commerce.cgi?product=CAR

the only thing you have to look very carefully is for the base, those are BA15 (15mm base) and they look just like BA20D base (200mm).


and form the same page DUQ posted http://autolumination.com/dcell1.html


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## NewBie

hotbeam said:


> Very noticeable turn-on time. Thanks for the vid Jar




No problem, anytime!


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## spock

just a small comment. few years back, some college did a study on perceived night distance using red, green, and blue lights. people had to judge how far they were from these simulated tail lights. red was judged to be further away than it actually was. green was judged to be the most accurate distance. blue was judged to be closer than it actually was. their conclusion: the safest tail light color was green, especially for rear end collisions. this did not take into consideration factors such as road conditions, tires, etc.. this summer i am going to see if i can duplicate these results on a small scale.


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## NewBie

spock said:


> just a small comment. few years back, some college did a study on perceived night distance using red, green, and blue lights. people had to judge how far they were from these simulated tail lights. red was judged to be further away than it actually was. green was judged to be the most accurate distance. blue was judged to be closer than it actually was. their conclusion: the safest tail light color was green, especially for rear end collisions. this did not take into consideration factors such as road conditions, tires, etc.. this summer i am going to see if i can duplicate these results on a small scale.



Unfortunately, Green means put the pedal to the medal!


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## NewBie

I just thought I'd mention, the tail light is still working great as we approach 2 years now.


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## PlayboyJoeShmoe

When I was experimenting with LED replacement 1157s, I found that the reflector in all the lights I tried was ineffectual with the narrow angle LEDs. And just the bulb itself radiating forward didn't have the needed power/brightness.

The LEDs that are on the vast majority of the 18 wheelers are round or oval rubber mounted modules that are indeed BRIGHT and NOTICEABLE!!!

I've given more than a bit of thought to adding a pair of those either in holes cut in my liftgate or with add on brackets...

I know I don't have the skill/knowledge to LED mod my tail lights!!!


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## MikeHunt79

Thanks for the info Newbie.  This gives me even more incentive to finish my conversion.

The red lux III's will give out 190 lumens at 1.5amps. This will probably be similar brightness to a 20w incan after it's been thru a red filter.

I'm currently replacing all my rear light on my car with LED's. It should be good when finished, and my car is 15 years old so the electrical system is nice and simple.  Also, a 3.3v DC-DC PSU can be made for around $15 so this shouldn't cost the earth to do either.


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## Eugene

Hey, perfect timing. I need a LED brake light, well CHMSL to be exact. I picked up a cap for my truck but it doesn't have the light and blocks the one from the cab. I don't want some young girl in a little Toyota to mess up her car rear ending me again like the one did a few years back because she "didn't see any brake lights" because my old truck didn't have one there. Anyone know of one for a good price, I stopped by Napa and found one there for $60. Since there isn't a light there I can't just use one of the bulb replacements listed above.


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## PlayboyJoeShmoe

If you were to somehow mount one of those oval multi LED modules I see on a LOT of 18 Wheelers I think no one would miss it!


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## Eugene

Good Idea, I found one at Waytek Wire for around $20, think I will order it. The cap is an earley fiberglass one, its a thin fiberglass shell with a frame under like the old aluminum ones so I could easily cut a hole in it to mount one.


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