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Old 31-12-2011, 15:10   #1
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Hot LED lights.

So, Since the Internet seems to have degraded into a venue for people to sell things, I can't seem to find any information.

That being said, I am wondering why it is that an LED light would heat up.

I have Tried the obvious such as checking the wiring and switching.

I have also re-soldered the connections directly to the LED plate thinking that maybe they might be loose....

Any Advice would be nice.
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Old 31-12-2011, 15:15   #2
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Re: Hot LED lights.

Greetings and welcome Aboard the CF, Dirty.

I’ve never seen a “hot” LED light; and cannot imagine why one might heat up (& not burn out).
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Old 31-12-2011, 15:19   #3
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Re: Hot LED lights.

I know.

I can't figure it out either....

The ol' "If you can't fix it yourself/ build a new one then Why is it on board" is coming true again...

Too Bad I there's no more whale fat for lamps around . HA!
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Old 31-12-2011, 15:34   #4
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Re: Hot LED lights.

All LEDs need a heat sink to get rid of thermal energy. If your design is shoddy, the heat will buildup until the temperature rises really high and bad things happen. LEDs are nearly 100% efficient, but they do produce heat (not nearly as much as other technologies.)
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Old 31-12-2011, 17:05   #5
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Re: Hot LED lights.

If too much current is being pushed through them, they will not only heat up, but the hotter they get, the more current they draw, making them hotter etc, until they burn out. Thermal runaway...
Put an ammeter on them to see how much they are drawing.
Small ones such as power indicators shouldn't draw more than 20 milliamps.
That's 0.020 amps.
At that current, you shouldn't be able to feel any heat to speak of.
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Old 31-12-2011, 17:13   #6
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Re: Hot LED lights.

I was assuming this was something more like a spotlight or high intensity nav light.
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Old 31-12-2011, 17:17   #7
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Re: Hot LED lights.

Many of the newer LEDs are much hotter than the older, low power LEDs. They also put out much more light than the older LEDs. Also, some assemblies have more than one LED on the pc board. Just search on "LED assembly heat output" and you will get lots of info.

What is the LED assembly that you are interested in?
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Old 01-01-2012, 04:05   #8
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Re: Hot LED lights.

LED, particularly high powered LEDs do develop a reasonable amount of heat. Thermal management (getting rid of the heat) is an important part of the design. Unfortunately heat sinks are expensive and bulky and many cheaper fittings skimp on them. They get hot and the lifespan and output of the LED suffers dramatically.
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Old 01-01-2012, 12:55   #9
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Re: Hot LED lights.

Quote:
Originally Posted by Dirty View Post
So, Since the Internet seems to have degraded into a venue for people to sell things, I can't seem to find any information.

That being said I am wondering why it is that an LED light would heat up?

I have Tried the obvious such as checking the wiring and switching.

I have also re-soldered the connections directly to the LED plate thinking that maybe they might be loose....

Any Advice would be nice.
First is how a LED works.

It's a semiconductor that uses different chemicals to determine the color output.

You can't control the voltage drop. It's controled by what the LED is made of. For light in the white range it's about 3.5 VDC.

Next is it is a current device. If you control the current you can make it put out light. So if you forward bias the LED (diode) with enoough voltage (3.5V) and supply a current the LED will produce light. The designers can vary the current thru the device.

The specifications from the designers specify 20ma (millamps) as a good point. You get so much light at that point. Less current for less light and more current for more light.

Heat is generated with every semi-conductor junction. The heat is measured in watts using the formular watts = volts X Current.

So for this case its the 3.5 volts times the 20 MA or 3.5 X .020 = .07 watts.

.7 watts is not much. If you touch the LED you would most likely feel some heat. The light output is much greater than of a tungston light with the same current. That amount of current thur a tungston light would most likely not cause the tungston to glow to produce light.

The more current you put thru the LED the brighter (more light) is produced. More heat is generated or consumed by the LED. Heat is one of the main cause of falure for semi-conductors.

So the designers of LED went down the path of lets have a path to get rid of the heat. They designed and manufactured LEDs on a heat sink. With this design more current can be used in the LED with the heat sink removing the heat, the LED will produce more light and last a given amount of time. I've seen design specs with 400 ma as the working current.

So now we are at 400 ma times 3.5 volts or 1.4 watts. Still a lot better than the tungston light.

So the answer to your question of ,
Quote:
Originally Posted by Dirty View Post
That being said I am wondering why it is that an LED light would heat up.
is heat is always produced in a semi-conductor (LED) junction. The amount of heat generated can by regulated by the current thru the LED.

What did you buy? Provide the link to the device so I can see exactly what you bought.

You also mentioned soldering to a plate. I can olny assume that you bought one of those so called high powered LEDs. Individual LEDs have pins not plates. Does it have a built in current regulating circuit? If you just bought the LED assembly you still have to have a way of rugulating the current thru the LED. If you don't regulate the current and put too much voltage across the LED you will generated lots of heat and most likely have a thermal runaway as others have posted.

Hope this helps.

Gordon
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Old 01-01-2012, 15:06   #10
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Re: Hot LED lights.

" I am wondering why it is that an LED light would heat up."
They are powered by the demon electricity and all demons carry hellfire and brimstone. End of question?

LEDs generate heat because there is electricity running through them. As you increase the power (mainly the current) they generate proportionately MORE heat, so if you are not properly regulating the power supply you will heat them up and burn them out. "Properly" means keeping the voltage and (mainly) current below the manufacturer's recommendations based on heat sinking and ambient temperature, and yes, there are extensive documents and charts for all that when you buy prime components as opposed to surplus parts from a junk shop.

Loose connections can cause heat but the odds are you are supplying too much power for the ambient temperature and the installation. "Too much" is also a sujective measure, because you can increase or decrease the life expectancy of an LED by more than tenfold as you change the current. And often change the birghtness, although that's more like just a twofold range before it goes POP and blows up from too much power.

"Proper" accepted ratings usually give the LED something like a 50,000-hour life before the birghtness dims by half.
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Old 01-01-2012, 15:24   #11
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Re: Hot LED lights.

An LED in the forward direction is basically a short circuit, which is why they need a resistor to limit current.

We were originally sold the idea of LEDs, because they used far less current than incandescent bulbs. That is certainly true for a single LED, versus a single incandescent bulb. But the newer bulb replacements with multiple LEDs, and an amount of heat would seem to defeat the purpose. Does anyone know how the newer multiple LED lights compare to a single incandescent bulb? I don't see much savings in actual power consumption.
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Old 01-01-2012, 15:39   #12
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Re: Hot LED lights.

I have cheap LEDs that I purchased a while ago that put out a rather impotent amount of light versus the sensibulbs that have been going strong for over a year now. The sensibulbs are bright, cool, and use almost no power. Can't love them anymore than I already do.
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Old 01-01-2012, 15:44   #13
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Re: Hot LED lights.

High quality "white" LEDs will dissipate approximately 1/7 the amount of power that an incandescent bulb will for the same amount of illumination. Quite significant yet not zero, as some of you wish for.
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Old 01-01-2012, 16:20   #14
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Re: Hot LED lights.

Cap-
"Does anyone know how the newer multiple LED lights compare to a single incandescent bulb?" You compare them by reading the power ratings that came with them. If an LED "group" consumes 1.5A that's the same power as a tungsten bulb rated at the same 1.5A, the only question left is what are the light outputs. Amps you measure with an ammeter, light output with a light meter although that gets trickier because you have to measure dispersion and area not just brightness.

If you bought cheap LEDs that use resistors to regulate current, you bought cheap and paid dearly. Using a regulator chip instead of resistors is more expensive, but it cuts the amount of power consumed. And depending on the regulator type, it may or may not cause radio interference as well.
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Old 01-01-2012, 16:24   #15
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Re: Hot LED lights.

Quote:
Originally Posted by rebel heart View Post
I have cheap LEDs that I purchased a while ago that put out a rather impotent amount of light versus the sensibulbs that have been going strong for over a year now. The sensibulbs are bright, cool, and use almost no power. Can't love them anymore than I already do.
AMEN !!

After biting the bullet of the purchase price, I'd do it all over again if I had to.

NO RFI at all.
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