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Old 09-08-10, 09:47 PM   #11
RobertSmalls
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When I saw Edison screw LEDs at Sam's Club (the kind that fit in a light bulb socket), I was excited. Then I crunched the numbers on lumens per Watt, and I was disappointed. They're a little more efficient than CFL's, but not much.

My GE EnergySmart 13W bulbs are rated for 825lm, or 63lm/W.

The white StarLED is rated for 87lm/W, before the 120VAC->3.3VDC power supply and regulator.

LEDs have advantages over fluorescents, but the ones I've seen so far don't save substantial energy when you need hundreds of lm.

LEDs have a big advantage if you only need a few dozen lm, though. I'm using a 12V T10 automotive LED to light my desk at night, which saves me from having to turn on a 13W CFL. It's powered by my PC.

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Old 09-09-10, 05:37 AM   #12
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One point I should have mentioned for those who might want to try this out: the variable resistor (trimpot, trim potentiometer) has three pins. Use the center pin and one of the outside pins, either one.

This system is meant for a non-technician like me to be able to build. Generally, in an LED circuit, a current controller is preferred over a voltage regulator. I don't know of a current controller than can be easily built. The LM317 can be used as a current controller, but it needs a 2W resistor to do that. I could not find resistors of the right ohm value in 2W. Voltage control is easy and uses cheap components. A constant current controller or pulsed system would be better but then the cost goes up.

There are 3W star LEDs on the same page as in the link above. I recommend trying them out. They should work with the same circuit. I have not tried the 3W LEDs yet.

Running 4 of these LEDs would require a voltage of just under 13.2V. They might work on a 12V battery, depending on your battery state of charge. The LEDs would dim as your battery voltage dropped. However when you turn a battery charger on, there would be voltage over the rating for these LEDs.
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Old 09-09-10, 07:41 AM   #13
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Quote:
Originally Posted by RobertSmalls View Post
When I saw Edison screw LEDs at Sam's Club (the kind that fit in a light bulb socket), I was excited. Then I crunched the numbers on lumens per Watt, and I was disappointed. They're a little more efficient than CFL's, but not much.

My GE EnergySmart 13W bulbs are rated for 825lm, or 63lm/W.

The white StarLED is rated for 87lm/W, before the 120VAC->3.3VDC power supply and regulator.
Ditto, I have yet to see LED far surpass CFL efficiencies. Also, work is still being done with CFLs to increase efficiency further.


Quote:
LEDs have a big advantage if you only need a few dozen lm, though. I'm using a 12V T10 automotive LED to light my desk at night, which saves me from having to turn on a 13W CFL. It's powered by my PC.
Thats a great idea. How did you tap into the 12V supply? Got any pictures of the setup?
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Last edited by Daox; 09-09-10 at 07:44 AM..
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Old 09-09-10, 08:11 AM   #14
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Quote:
Originally Posted by skyl4rk View Post

Running 4 of these LEDs would require a voltage of just under 13.2V. They might work on a 12V battery, depending on your battery state of charge. The LEDs would dim as your battery voltage dropped. However when you turn a battery charger on, there would be voltage over the rating for these LEDs.
There are on-line programs for building lm317 regulators on the web.
I built one last July.. http://ecorenovator.org/forum/projec....html#post7318

And, there are wiring diagrams & component layout info too.
Building this supply should be pretty easy for novice techs.
However, if the 317 gets hot, you might want to think about a heat sink.

Anyways, heating up a regulator chip is actually wasting power,
when you could just stick in a 4th LED..

And of course don't try to charge your battery!

I'm thinking a 4-LED 12v lamp for battery only. I have a big lug-able
12v LA battery that we use during short grid failures.
http://i46.photobucket.com/albums/f1...Solar/r068.jpg
Normally it has a 12v halogen lamp plugged in, but I think 4 LEDs
might give more light for less watt hours.
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Old 09-15-10, 11:20 PM   #15
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Most of the lighting in our motor home (we are full timers) are LED, we paid $29 each for 8 MR16 lamps in track lighting, and about $21 each for about 7 superbright leds 9emitter circuit boards, we don't even think about the energy consumption when we are living off grid - most of the winter, our PV panels and batteries provide lots of light.
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Old 09-15-10, 11:25 PM   #16
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There are emitters now on the market that put out well over 100lumens/watt. Cree has announced a 208 lumens / watt emitter, that will be on the market soon, Unless you want stark light, make sure you buy warm white 3,000K +/-
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Old 11-01-10, 11:28 AM   #17
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I was just looking at those 3.3v 1W Warm White LEDs again..

Then, I went down stairs and looked at my two 12v batteries.
Both were indicating a full charge. Both measured at 13.2 volts.

13.2 / 4 =3.3 volts, so I'm thinking that 4 of those LEDs might be plug-n-play on one of my batteries..


The LED lighting would be off during the day.. So charging voltage should not be a problem..

A 4.62w lamp, off a fully charged car battery should last a while..


So, what is the operating temperature of these LEDs??
Do they need to be installed on a heat sink?

Thanks,
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Old 11-01-10, 07:38 PM   #18
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The star acts as a heat sink so you don't need any additional heat sink. They do get warm, not quite finger burning warm but close to pain warm.

I would give them a try with 4 stars at 13.2V. You may want to pay a bit more for the 3W version. I have not tried them yet but will soon when the next shipment gets in from Futurelec. I am hoping that 3 - 3W warm whites will be equivalent to a 100W incandescent bulb.
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Old 11-01-10, 09:59 PM   #19
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I've not seen any specs on the 3w LEDs. They seem to have the best w/$
at $1.63 per watt. (vs $3.20 a watt for the 1w LEDs).

Is the forward voltage 3.3v ??


And, how is the shipping cost at Futurlec?

Thanks,
Rich
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Old 11-02-10, 05:48 AM   #20
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Shipping cost is pretty low, it is based on the dollar value of your order. Futurelec is in Thailand and charges you in Australian dollars so there is also a fee for that on the credit card, a dollar fifty for my card.

I'm not sure that Futurelec is the cheapest or best place to get them, there may be better places.

Shipping time is slow, three weeks is not uncommon.

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