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Old 07-09-2007, 05:18 PM
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How much faster do LEDs illuminate???

I asked myself this question several times, and just could not for the life of me believe that they light up that much faster.

Today, on my way home from work, I was following a semi/container truck, that had LEDs and incadescent lamps on the rear. All wired together.
2 LED and one regular on each side.

When this guy signaled or applied his brakes---THE LEDs CAME ON 1/2 SECOND FASTER!!!

I never would have believed this if I had not seen it for myself.

This is just a general observation for those that may or are considering LED lightin in the rear.

Bryan

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Old 07-09-2007, 05:39 PM
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Doc here,

This might be the way the two systems you were watching were multiplexed..(assuming each system had it's own trigger separate from the other system for isolation) I.E. the LED Brake Lamp may come in to contact a smidge faster than the one for the incandescent lamps because of mechanical adjustment..

Granted LED's are way faster in Strobe applications an incandescent could not keep up..but in static applications I doubt the naked eye could detect the difference..given all else being equal. Speed of light is the speed of light..

Might be an interesting bench test though..Your bench or mine?

Doc
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Old 07-09-2007, 06:51 PM
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I don't know if this proves anything or not, but when the NHRA switched to LED lamps on the starting tree it took a while for the drivers to get used to them and get their reaction times dialed in. It was said that driver concentration was so intense that they could actually see the filaments in the incandescent bulbs begin to glow. LEDs don't have filaments and the drivers had to adjust to them.
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Old 07-09-2007, 09:22 PM
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Doc here,

I hear that..you'd have to have an awful sharp Eye to see the gas fire across the Cathode and anode of an LED..

Plus , I believe those are diffused light..which makes it much harder to "focus" on in a Tree application..

Doc
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Old 07-09-2007, 09:46 PM
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Quote:
Originally Posted by Bryan59EC
I asked myself this question several times, and just could not for the life of me believe that they light up that much faster.

Today, on my way home from work, I was following a semi/container truck, that had LEDs and incadescent lamps on the rear. All wired together.
2 LED and one regular on each side.

When this guy signaled or applied his brakes---THE LEDs CAME ON 1/2 SECOND FASTER!!!

I never would have believed this if I had not seen it for myself.

This is just a general observation for those that may or are considering LED lightin in the rear.

Bryan
I've noticed this before too. The bus I ride to work has LED and incandescent lighting on it. Here's what I'm thinking. Incandescent bulbs use more energy, they create heat and light. LEDs create little, if any, heat. Just light. Meaning they would illuminate faster. Right?

LEDs are way cool, I bought a set for my boat trailer. I wonder how they would work as household lighting if they used with a diffuser? How about as high beam head lights?
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Old 07-09-2007, 10:20 PM
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Quote:
Originally Posted by Blazin72
I've noticed this before too. The bus I ride to work has LED and incandescent lighting on it. Here's what I'm thinking. Incandescent bulbs use more energy, they create heat and light. LEDs create little, if any, heat. Just light. Meaning they would illuminate faster. Right?

LEDs are way cool, I bought a set for my boat trailer. I wonder how they would work as household lighting if they used with a diffuser? How about as high beam head lights?

Doc here,

They DO make LED's for home use..IIRC, very Expensive though last time I looked..

I don't know if the Tech is up to High Beams yet though..

In theory..(only) If both were on separate Circuits..side by side..the naked eye should not be able to see a difference if both were lit at exactly the same time..

My thoughts on this is possible use of duel trigger switches for isolation of circuits between the incandescent and the LED circuits (as we see they don't play well with others on their own..) and one triggers slightly after the other.

OR If a load resistor was being used, For draw against standard Flasher, that might account for the delay..

I think , I am going to set up a test on a piece maybe next week or so, of perfboard with both Lamp forms on it from a common supply, and see if there is a delay or if both light at the same time..(which they should) Would be interesting to know..

Doc
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Old 07-09-2007, 10:30 PM
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Quote:
Originally Posted by docvette
Doc here,

They DO make LED's for home use..IIRC, very Expensive though last time I looked..
I think , I am going to set up a test on a piece maybe next week or so, of perfboard with both Lamp forms on it from a common supply, and see if there is a delay or if both light at the same time..(which they should) Would be interesting to know..
I wonder how the light would turn out for home use. LEDs strike me as having a somewhat harsh light. I might have to find a place to check them out and see what they're like.

I'd like to hear what you come up with when you do your comparison. Should be cool.
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Old 07-10-2007, 06:12 AM
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My wife saw some info about the home LED's. I looked them up and they were approx. $30 - $60 per bulb. Plus, the ads weren't clear as to whether you could just screw them into a regular socket or if you had to have special fixtures and transformers. Additionally, they didn't seem to have a good correlation to standard bulb wattages so you would know if you would be living in a black hole or blinded. I think it is more of a "green Heathkit" type of program for now. Primarily for the ultra save the earth types or the fringe DIYers.

I haven't raced since they went LED bulbs on the tree. I know that with the old 1/2 second (or 0.400 second) bulbs, I could see the filament start to glow, grow to full bright, and then dim to off. That would be how I would adjust my leaving time. My understanding is that the LED's are much closer to instant on and the naked eye can't see changes.
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Old 07-10-2007, 02:46 PM
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Light bulbs take a lot of current to heat the filament hot enough to glow. As Doc said, LED's have no filament and thus use a lot less current. It takes time to heat the bulbs filament hot enough to glow, while LED's produce light almost instantaneously, or at least fast enough that you would need a high speed camera to catch it.


The best example on the roads today are pickup trucks/suv's that have the LED turn arrows in the mirrors. I see them all the time and yes, the LED's light noticeably earlier than the bulbs. If you watch close enough, you can see the LED go out before the bulb as the filament cools.
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Old 07-10-2007, 03:33 PM
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Quote:
Originally Posted by docvette
Granted LED's are way faster in Strobe applications an incandescent could not keep up..but in static applications I doubt the naked eye could detect the difference..
i assure you you can tell the difference, its easy

the "warm up" time for an led vs an incandescent its pretty different, so is the "cool down" time

try it, place an led and an incandescent next to each other behind a sheet of paper, right next to each other, hook up the grounds, and mix up the positive wires ... tap the wires one at a time on the battery post

hence why led's make better strobes ... if the human eye couldn't tell the difference then incandescents would make just as good of a strobe, right?
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Old 07-10-2007, 04:56 PM
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LED's are way faster than normal bulbs. An LED can turn on and off in milliseconds, basically instantly. it is on before your eye knows it.

For example LED clocks scan the LED's turning digit one on, then off, then the next digit untill they all have been updated, then do it again. Each digit is turned on and off something like 1000 times a second ( or more I forget )

an incandesent takes forever to heat up, I believe the 1/2 second guess above.

Keith
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Old 07-10-2007, 05:03 PM
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Quote:
Originally Posted by lowROLLERchevy
i assure you you can tell the difference, its easy

the "warm up" time for an led vs an incandescent its pretty different, so is the "cool down" time

try it, place an led and an incandescent next to each other behind a sheet of paper, right next to each other, hook up the grounds, and mix up the positive wires ... tap the wires one at a time on the battery post

hence why led's make better strobes ... if the human eye couldn't tell the difference then incandescents would make just as good of a strobe, right?

Doc here,

Actually, and I guess most people don't know it..

AC Incandescent Lamps are Strobes..It's the way they work..

Every 60 Hz The cycle reverses, effectively shutting the filament down for a micro second..while that process occurs..this is / May be why we perceive DC Lighting more Harsh to the Eye than AC lighting..

DC incandescent Must heat and warm the filament to glow..that takes time..a Gas Filled or LED lamp only has to blast a spark through the media to produce 100% peak output..as far as candle power..

Another reason there is very little draw from LEDS..No filament resistance (like 1.0 Ohms ..you do the math..) To ground. Just whatever small amount of resistance the media offers.

Doc
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Old 07-10-2007, 05:10 PM
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Originally Posted by redsdad
My wife saw some info about the home LED's. I looked them up and they were approx. $30 - $60 per bulb. Plus, the ads weren't clear as to whether you could just screw them into a regular socket or if you had to have special fixtures and transformers. Additionally, they didn't seem to have a good correlation to standard bulb wattages so you would know if you would be living in a black hole or blinded. I think it is more of a "green Heathkit" type of program for now. Primarily for the ultra save the earth types or the fringe DIYers.
Doc here,

That's one of the reasons those "Home LED's" are so spendy..

The base of the bulb is actually a small step down transformer, an AC to DC rectifier, and some sort of output ripple filter (semiconductors Don't like AC at all.)

When they figure out how to reduce it down to a single chip smaller than your fingernail, and can produce them at 1/8 of a cent per..the costs will come down..Then the only hurdle is the power producers

Doc
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Old 07-10-2007, 05:27 PM
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Originally Posted by lowROLLERchevy

hence why led's make better strobes ... if the human eye couldn't tell the difference then incandescents would make just as good of a strobe, right?
Doc here,

LED's Make better strobes because of the way they operate..and the speed at which they can obtain an "ON" state..

As we all agree..an incandescent must start and warm a filament through series resistance to ground..that requires Time..an LED only must shoot a spark through media to gain full potential with little resistance to ground. Whatever leaks across the Cathode and anode through the media..but no direct coupling to a ground.

At certain slow speeds I assume both operate *almost* (to the naked eye..be advised..I have bad ones ) comparable (Dono..never tried it..but I will be benching it maybe later next week for something to "Play" with , I'll let ya now..) But as that speed increases , or the speed of the time base powering the LED, It leaves the Incandescent in the dust..

Much like the age old.."Why is a Module faster and more Efficient than a set of points.." Because you take both the Analog and the mechanical out of the equation..at a given speed each pulse produces the same pulse as the last without mechanical error, or "drop Off" of analog..

Doc
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Old 07-10-2007, 05:55 PM
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Originally Posted by docvette
Doc here,
At certain slow speeds I assume both operate *almost* (to the naked eye..be advised..I have bad ones )
Doc

Was gonna make a comment on this earlier, but had no opportunity to put a humorous spin on it

'Self proclaimed blind guy doing speed checks'

Anyway Doc, be real cool to find out for sure----be sure to let me (and the rest of us) know what you discover.

(new 'puter--new keyboard--Microsoft Vista------All pissn me off------won't let me do what I want it to do )
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