Author Topic: My attempts on white LED  (Read 6083 times)

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prasadbodas2000

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My attempts on white LED
« on: July 24, 2011, 07:50:23 AM »
pls see attached a LED lamp assembly I made using 24 number (supposed to be) 1/2 Watt (3.6V driven) LEDs, these have a lense which does not make a spot focus but spreads the light. I could drive only upto 1/4 Watt w/o generating much heat, but these are a nice setup in a small room of 4x6 feet (typically a toilet or bathroom). In such places a 5W CFL would be generally used, but it is seen that due to too frequent switch-on/off (20-30 per day) of the CFL it gets damaged and does not work after about 7-12 months.

As you can see there is a LM317 current limiting circuit mounted on the aluminium sheet, which is used to mount the LEDs

These are set up as 8 parallel arrays of 3 each in series.

Out here in India they costed me Rs 10 each + Rs. 10 for LM317 + others = Rs. 280 approx = 6.2 USD, and a 5 Watt CFL costs Rs 110 = 2.44 USD

Comments and suggestions please....



« Last Edit: July 28, 2011, 01:35:07 PM by kurt »

dnix71

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Re: My attempts on white LED
« Reply #1 on: July 24, 2011, 02:30:58 PM »
2 watts of LED will light a small room well enough to read if done correctly. Heat is what kills LED's, so unless you have a good heat sink, running them 1/2 rated power is the safe way.

http://fieldlines.com/board/index.php/topic,145605.0.html has a picture of my bathroom lighted with 2.2 watts of surface mount LEDs. Two 120vac candelabra-base store bought. The price is way too high for common use, even in the US, but it shows what's possible. The package says they are rated 20k hours - 3 hours/day 7 days/week for 2 years.

It should be possible to do much better than that if they aren't pushed so hard. The camping LED disk lights sold for about $10 US that use 3 AA batteries don't last very long either, but they are bright enough to light a 10'x10' room well enough to read. They also melt from overheating if left on too long.

Since you have a lot of time invested in making this, definitely keep the power down, and if you can get it for cheap, maybe put just a small dab of heat sink grease around each LED to keep them cool.


snake21

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Re: My attempts on white LED
« Reply #2 on: September 09, 2012, 02:11:53 PM »
hello,just want to share.
i have just made 2 40w car fog lights. they are around 4500lm both.
now i am on my way fabricating headlights with a 20w led bulb. i think it should be working in 2 weeks time.

i am using aluminium rod to fix the bulb and at the end of the rod,there will be a computer heatsink without fan.

i guess 20w led is equivalent to a 100w halogen bulb.

if i have some time,i might post the pictures for you guys.

DamonHD

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Re: My attempts on white LED
« Reply #3 on: September 09, 2012, 03:13:58 PM »
Sounds good snake.

Yes, I guess 5:1 lumens for LED:incandescent is about right at least as a first guess and provided that your LED driver is efficent!

Rgds

Damon

tanner0441

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Re: My attempts on white LED
« Reply #4 on: November 13, 2012, 06:29:38 PM »
Hi

I have just bought several 240V 3W LED lamp units, they were 5.99GBP each but they give the light output that compares if not exceeds the light output of a 40W incandescent lamp. They are a little bit larger than a golf ball and after running all evening they are still cold to the touch. I have one in a bulkhead light outside and it lights a 40ft by 40ft yard enough to walk about after dark, and as the dusk dawn sensor has died it is on 24hrs a day.

I tried three of them in a three way pendant fitting but although adequate in a room they c olour was a bit stark. If I have a criticism it is the colour temperature they are around the 5000K and for domestic use they would be better around 4000K.


Brian

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Re: My attempts on white LED
« Reply #5 on: November 18, 2012, 09:48:10 PM »
... and after running all evening they are still cold to the touch.

"cold" or cool is good.
Some of the cheap ones have a converter that get dang hot.
When the converter overheats, the bulb fails.
www.ghurd.info<<<-----Information on my Controller

tanner0441

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Re: My attempts on white LED
« Reply #6 on: November 19, 2012, 07:40:10 PM »
Hi

They seem to a steady temperature I put one in an outside bulkhead fitting it has now been running 24hrs a day since I put it in over a week ago. The only annoying thing is they're E27 and E14 and most of my ceiling fittings are bayonet so I have to use adapters.

Brian