LED lights - Page 2 - Fiberglass RV


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Old 12-24-2011, 12:47 PM   #15
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Compare: LED Lights vs CFL vs Incandescent Lighting Chart

Here is a site that shows useage
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Old 12-24-2011, 01:42 PM   #16
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LED efficacy

I would be careful with some of these efficiency claims especially if they use 60W incandescent bulb as reference point instead of lumens/watt. There are some LEDs with 250 lumens/watt efficacy but it will take some time to see them in real life. The following two PDF documents could have too much information but it is good stuff. One is from 2008 and the other one from 2009 but I still think they are relevant.

http://apps1.eere.energy.gov/buildin...white_leds.pdf

http://cool.conservation-us.org/byor...white_leds.pdf

George.
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Old 12-24-2011, 02:14 PM   #17
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Originally Posted by GeorgeR View Post
I would be careful with some of these efficiency claims especially if they use 60W incandescent bulb as reference point instead of lumens/watt. There are some LEDs with 250 lumens/watt efficacy but it will take some time to see them in real life. The following two PDF documents could have too much information but it is good stuff. One is from 2008 and the other one from 2009 but I still think they are relevant.

http://apps1.eere.energy.gov/buildin...white_leds.pdf

http://cool.conservation-us.org/byor...white_leds.pdf

George.
Don't be mislead. These comparisons are lamps used in household current fixtures. LED's are approximately 2volt devices and DC devices, perfect for 12 volt trailers. However they require some different technical stuff for 120AC applications.
My measurements for an 1157 LED replacement lamp
Current = .2 amps
Power = (.2x12) 2.4Watts)
Lumens = 252 (per specifications)
efficiency in Lm/W = 252/2.4 105 Lm/W

In this case the efficiency in Lumens per Watt is higher for LEDs than any other light.
I agree with the findings shown in those documents for 120VAC applications. It's a bit more difficult to efficiently alter AC to work with DC devices, than to use DC devices with DC. However, improvements are happening rapidly.

I won't go into all the technical jargon to explain why.


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Old 12-24-2011, 03:08 PM   #18
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Get the Alternating Supply down to the correct voltage and the LED works without a problem as a half wave rectifier.

Take your Christmas LED rope light and wave one end back and forth with the light on and it will appear as though the light is blinking on and off and that is because it is only on during the AC cycle.

If it does not blink on and off when you do that then it is full wave rectified and turned on , on both cycles of the AC
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Old 12-24-2011, 03:23 PM   #19
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Originally Posted by Darwin Maring View Post
Get the Alternating Supply down to the correct voltage and the LED works without a problem as a half wave rectifier.

Take your Christmas LED rope light and wave one end back and forth with the light on and it will appear as though the light is blinking on and off and that is because it is only on during the AC cycle.

If it does not blink on and off when you do that then it is full wave rectified and turned on , on both cycles of the AC
Agree, and if 30/25Hz is too annoying full wave bridge is just a little more money.
George.
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Old 12-24-2011, 05:42 PM   #20
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Originally Posted by Darwin Maring View Post
Get the Alternating Supply down to the correct voltage and the LED works without a problem as a half wave rectifier.

Take your Christmas LED rope light and wave one end back and forth with the light on and it will appear as though the light is blinking on and off and that is because it is only on during the AC cycle.

If it does not blink on and off when you do that then it is full wave rectified and turned on , on both cycles of the AC
That also means only half the light output.
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Old 12-24-2011, 06:57 PM   #21
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[COLOR="rgb(154, 205, 50)"]
Quote:
It's a bit more difficult to efficiently alter AC to work with DC devices, than to use DC devices with DC.

That also means only half the light output.
[/COLOR]
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Byron, You are absolutely right, 1/2 the light on a 1/2 wave with nothing more than the correct resister in line with the LED. AC Altered in the simplest form.

Merry Christmas to all.
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Old 01-03-2012, 03:06 PM   #22
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It is difficult to trust any site that is trying to sell new product. When I looked into it about five years ago, LED`s were slightly less efficient (lumins / watt) then florescent. I am sure that as technology progresses, the LED have become more efficient then florescent. The claim that they are twice as efficient seems doubtful to me, but maybe.

I generally laugh at people who quote Wikipedia, but the numbers on Wikipedia look believable to me.
Luminous efficacy - Wikipedia, the free encyclopedia
For a florescent light, the ballast has a large effect on the efficiency. With an electronic ballast, florescent has an efficiency of 80 to 100 lm/W vs. 4.5 to 150 lm/W for a raw LED. With a theoretical efficiency of 300 lm/W, (44%).

LED's have many other advantages as well. Bulb life is hard to beat, cold temperature performance, compact form, fits in existing fixtures, cheep, low voltage performance, arguably better light quality, .... LED's are obviously the future.

The only point I was trying to make is that it may not yet make sense from a cost vs benefit point of view to change from florescent to LED.
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Old 01-05-2012, 01:26 PM   #23
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It's a bit more difficult to efficiently alter AC to work with DC devices, than to use DC devices with DC.

Appears there is no dificulity at all to make a DC LED to operate on AC.
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Old 01-05-2012, 01:40 PM   #24
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Originally Posted by Art VanDelay View Post
It's a bit more difficult to efficiently alter AC to work with DC devices, than to use DC devices with DC.

Appears there is no dificulity at all to make a DC LED to operate on AC.

Would you mind describing how it done in both AC and DC cases?
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Old 01-06-2012, 02:14 PM   #25
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Originally Posted by Art VanDelay View Post
It's a bit more difficult to efficiently alter AC to work with DC devices, than to use DC devices with DC.

Appears there is no dificulity at all to make a DC LED to operate on AC.
It depends a bit on the device. I have several "AC" devices, like my little Radio/DVD/TV system that are designed for installation under a kitchen cabinet, that use "wall wort" AC adapters that step down to 12 volts. To install devices like these all you have to do is wire up a connection between the correct sized plug for the device and your trailer's 12V system and (potentially) add a 12v voltage regulator.

A voltage regulator is helpful for sensitive electronic devices (including many LEDs) because trailer 12v charging systems charge the battery at 14-18 volts. The aforementioned radio/DVD/TV draws less than an amp most of the time with short peak draws of 1.2 amps when the DVD tray is inserting or ejecting a disk, so my regulator is a group of three bridge-wired 1-Amp 7812 voltage regulator chips.
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Old 01-06-2012, 06:27 PM   #26
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It appears to me that Art is having a bit of fun at Byron's expense.
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