LED Headlight

[redline5th]

Very cool! I enjoyed reading about your project.

[meelis11]

but what about powerleds? 3W Cree leds maybe?
Is it some way better to use more "standard" 5mm leds than fewer powerleds?

[wagonman76]

Well what I perceived as "warm" was slightly warmer than 20F. I tested them outside where I could see how far they would shine.

Even in the summer the chances of seeing 90F in Michigan is little to none. I could try running a few in a destructive test, leaving them on all day next to the woodstove and as long as they still work the amps should be ok.

One thing I like about using 3 in series is the resistor value is larger. It would handle voltage variations in the car without much change in LED amps. Using 4 in series means a smaller resistor and though they worked nice with my steady power supply, a variation in car voltage could either make them not work or could fry them.

[Nerys]

Like hell I was just at a Naram in Delton/Kalamazoo Michigan and it gets JUST as god damned hot their (over 90') as it does here in SE PA. I know I spent a week their.

I am sorry but anything colder than you can NOT be perceived as warm. its in defiance of the very definition of "warmer" and "colder" those terms are relativistic terms.

Warmer and colder THAN WHAT? well warmer and colder than YOU.

your 98' (close enough yes skin is colder than that)

Lower than 98 and your physical construct we call your body perceives "colder" higher than 98 and your body perceives warmth.

The point is if you PERCEIVE it physically as "warm" then its probably TOO WARM to be safe for the LED's unless you have a good heatsink on them.

I don't know why people are arguing with me over this crap. Its very simple.

HOT LED'S DIE. its that simple. They do not care if you believe it or not if you like it or not or percieve it as warm or not.

if you over heat an LED it will DIE. period.

Fact 2 - IT DOES NOT TAKE MUCH HEAT TO KILL A WHITE LED.

First the phosphor burns off (making them turn more blue/uv) and then they just DIE.

the higher the temp the faster the death. I had a tube of LED's hit 160's inside the tube. They were dead in 4 days.

I dropped the voltage down to 89volts (variac) so that they were 5' above ambient and they have been going for thousands of hours over the last 3 years without so much as dimming in the slightest.

I am just trying to help. I noticed you said they felt WARM and you were not even TOUCHING THEM.

this means they are way way way too hot. Don't believe me? put them INDOORS where it is warmer above 70'f plug them in at the same power and voltage and LET THEM RUN and let me know how long they last.

I give them a week. (if they really were warm feeling without you even touching them and were normal LED's with no heatsink.

Put them in an array of 50-100 LED's and see how much FASTER they kill themselves.

[Christ]

First sentence really wasn't necessary, was it?

I can see the point you're trying to get across, but I don't think those terms are doing it very tactfully.

[jonathan150cc]

Originally Posted by Nerys

I am sorry but anything colder than you can NOT be perceived as warm.

This is a faulty idea. The concept of hot and cold, warm/cool, is not based on your internal body temperature. The perceptions of these "feelings" is based on whatever climate you are accustomed to, not your physical temperature.

It's why people in FL wear jackets when the temp gets below 80 and people in Alaska are out in shorts in the 60s.

And it varies by seaons. It is completely normal and possible to enter a building in the winter where the interior temperature is regulated to something like 74 degrees and to feel uncomfortably warm. Why is that? Because you grew accustomed to the colder outside temp. You can't make the argument that somehow your core temp dropped below 74 so now you can sense the warm inside air. If that were true, you would be dead and you wouldn't be feeling anyting.

The concept of hot and cold is completely independent to the individual. You are correct that it is relative but it's not based entirely on your core body temperature.

[Nerys]

well the first sentence was supposed to be humorous "like hell" get it? (note kalamazoo was actually a fantastic place but it sure was hot that week)

Jonathan150cc. your right but your dead wrong.

If I say 2+2=4 and you say NO 2+3=5 your wrong.

are you wrong? YES you are because you provided an alternative correct answer that is completely and utterly UNRELATED to what is being discussed. so while your example is correct your still dead wrong because your correct answer is irrelevant.

MY contention is WARMER not "warm" Warmer requires something to compare it WITH (warm does not that only requires an example)

I specified if you FEEL WARMTH. this is the "compare it with" part. Not does your BODY FEEL WARMER but stick your hand onto something DOES IT SEEM WARMER do you perceive WARMTH. This has no connection or relationship to you feeling the room is too warm. Completely different concepts and sensations and conditions.

it is warmer RELATIVE TO YOU. relative to you is roughly 98' (yes I know skin temp can be in the eighties not the point)

the POINT of this is that over 100' = BAD for led's FACT

the point of this is that anything that FEELS WARM to a human being (not IS WARM but "FEELS WARM" is something your BODY says "hey" thats warm. will ALMOST ALWAYS be over 98' (humidity changes this for air temps hence why 80' and 90% humidty feels unbearable but 80' and 5% humidity barely even feels warm) this is more to do with YOUR ability to get RID of heat than of you feeling heat from outside. Another subject

We are talking localized here (stick your hand on it) your "entire body" warm concept is altered by the fact that we are WARM BLOODED so while a 90' room might be the same as your body temp YOUR BODY will alert you this is too much BECAUSE YOUR GENERATING HEAT and its harder to get RID of that heat into a heatsink that is 90' than one that is 75' so even though the 90' heatsink IS COLDER THAN YOU its not enough to work as an effective heat sink.

The POINT WAS I am trying to give you a sensible simple easy understandable way to determine if your LED fixture

IS GOING TO FRAKING MELT ITSELF

this is simple. TOUCH IT. if its warm to your touch ITS TOO WARM.

thats it.

I don't care about the concept of hot or cold.

I care about WARMER OR COLDER THAN YOUR TOUCH. this is NOT independent of the individual because WE ALL run at about 98' give or take a tiny margin.

NO its not because you grew accustomed to 74. its because your body started PUMPING OUT HEAT to keep you warm and now suddenly you in an environment that is much warmer than the last one you were in (outside) so your pumping out this heat and now can not get rid of it because your heat sink (the air) is not as good at sucking the heat from you anymore (because its warmer than outside)

SO your body tells you "i'm too warm" until it adjusts and cranks down the heat production to be inline with the environmental temperature. You forget that your SKIN is essentially a large RADIATOR and that we are WARM BLOODED we are essentially a heat furnace we MAKE OUR OWN HEAT and when there is too much we must get RID of that heat. This is why you sweat.

and last I checked the "air inside" never actually touches your "core" body parts. I imagine that would be pretty lethal since you would to be pretty darned broken to allow that to occur and the warmth of the air would be the last thing on your mind I imagine.

Think about it this way. WHY does your car have trouble cooling itself in 100' high humidty weather?

the air temp is LESS THAN HALF what your cars operating temperature is? its because while the temp is lower its ability to DRAW HEAT ie to Exchange heat with your radiator is much more limited. Colder but not enough.

[meelis11]

Nerys, has somebody told you that you speak too much?

Your answers are so long that I just give up.
No hard feelings, just wanted to say that you can make your point with much less words and sentences.

[Nerys]

except that the fewer the words I use the more "stretching" the answers become.

I guess I am not the greatest as expressing the concepts so I use more words to compensate for this lacking to hopefully reduce clarity problems.

Plus I started off pretty simple. If it FEELS WARM when you touch it its likely too warm since its likely over 98' and anything over 100' is bad for LED's

So I did start off pretty darned simple.

Was I unclear or were others just dense? (genuine question)

[meelis11]

That short version is clear enough to me.
Sometimes less is more

I asked before that why not to use few powerleds instead lots of normal leds. Anyone has the answer?