Low cost LED lights
 

Here is a homemade LED light that puts out roughly the equivalent of half of a 60W incandescent bulb, using 4W.

must ... reach ... 5 ... posts ....

This type of light could be used by people with a small solar/battery system to live off grid.

Parts list

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3 pcs 1W Star LED, rated at max 3.3V, $3.20
STARLED_1W_WW
Star LED

1pcs LM317T voltage regulator, TO-220 type, 1.5 amp design current, $0.65
LM317T LM317 - 1.5A Adjustable Positive Regulator
LM317 datasheet
Linear Series - Voltage Regulators

1pcs R220R12W 220ohm 1/2W 5% Carbon Film Resistor, $0.15 for 10
Resistors 1W

1 pcs TRIM5K 5K 1/4W Min. Horizontal Pot, $0.15
Trimpots

The voltage regulator circuit is shown on this pdf, on page 1.
LM317T Datasheet

Note that when looking at the LM317, the left pin is Adj, the middle is Vout, and the right is Vin.

To make the voltage regulator, connect the 220 ohm resistor between the Vout pin and the Adj pin. Connect the 5k variable resistor between the Adj pin and ground. Connect a 12V (nominal) battery power positive to the Vin pin, and negative to the ground.

The output voltage positive is at Vout, negative at ground. Adjust the variable resistor to get a voltage of just under 9.9V, which is three times the maximum voltage of the LED. The resistance is about 1400 ohms, but measure the voltage output.

Use 14 gauge solid insulated wire to connect the LEDs. This stiff wire allows the LEDs to be aimed as needed. There are positive + markings and negative - markings on the star LEDs. Connect the three LEDs in series, positive to negative. After making sure the voltage regulator output is not above 9.9V, connect the outer LEDs to the positive and negative output of the voltage regulator.

The light output of the three 1W LEDs is about equivalant to a 40W bulb, maybe a little less, and they use about 4W. Be aware that the LEDs and voltage regulator get hot.

Pretty neat.. I like it!

You need to edit the link for the LEDs.. Star LED

I'm wondering why you couldn't just use 4 LEDs across a 12v battery??

fixed ... thanks

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.

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.

Ditto, I have yet to see LED far surpass CFL efficiencies. Also, work is still being done with CFLs to increase efficiency further.


Thats a great idea. How did you tap into the 12V supply? Got any pictures of the setup?

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. :D

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.

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 +/-

I was just looking at those 3.3v 1W Warm White LEDs again.. :D

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..
http://i46.photobucket.com/albums/f1...Solar/z010.jpg

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,
Rich

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.

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

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.

You might be right, I just took a quick look on Ebay and found some interesting stuff.
I'll have to do a serious search this evening.. :)

This seems like something to try. I can't see how it has such a large voltage range..
White 8-LED Super Bright Car Light Bulb 3 Watt DC 8-30V - eBay (item 190459203966 end time Nov-20-10 07:52:49 PST)

Wow, a 10w LED for $7
http://imgs.inkfrog.com/pix/dxy_dxy/DSC00499_.jpg
10W 600LM Warm White Led High Power Lamp 10~12V F - eBay (item 170552346374 end time Nov-12-10 10:55:00 PST)

Or, a more finished look, 9W lamp for $6.39 ??
MR16 48 3528 SMD LED Bulb Lamp Light Warm White 12V 9W - eBay (item 230539862309 end time Nov-17-10 02:28:16 PST)

http://www.eshop111.com/ebay/xpicsc/tbv50bc.jpg

I kinda like the finished look.. :)

I wonder if one of these would make a good headboard reading lamp?

Anyways, perhaps 2 or 3 of these around the house as back-up lighting
or, maybe just standard evening back-ground lighting..?.

One or two of these shouldn't load down a LA battery too much..

Any comments on the specs?

It looks like these have a regulator and will work on battery power directly.

I would say that the stars that I have been experimenting with are old technology now, because these products are much higher wattage and much cheaper.

With those prices, LEDs will take over lighting from other bulb types soon.

I really like the 9W lamp for $6.39, but I know it's for indoor use, not for cars..
I don't think they have a regulator, and that makes me wonder how these would do when used with 13.8vdc??

With the SMD LEDs arrayed on the top like that, I wonder if these are less of a spot light
and more defuse / have a wider beam..?.

Power: approx. 9W
Diameter: 50mm
Height: 38mm
Luminous flux value: 200LM

That's only 22lm/W, a clear failure, close to the efficiency of an incandescent.

The 10W diode emits 600lm, or 60lm/W, which falls just short of a 63lm/W CFL. However, it doesn't include the power supply, and power supplies / voltage regulators on this scale are a big source of inefficiency for LED lamps.

Maybe it's only a 2.5 w lamp??
 

Humm, It sounded too good to be true..

MR16 48 SMD 3528 LED Low Voltage 12 V DC/AC LED Light - Low Voltage LED Lights - LEDLight

"
MR16 48 SMD 3528 LED Light. Very bright over 220 lumens uses only 2.5 watts of power very efficient LED Light. 12 VDC. Approximate size is 1.82in x 1.96in.
"

Hey, they made a movie about it.. :rolleyes:

YouTube - 38976 MR16 48 SMD 3528 LED Low Voltage 12 V DC/AC LED Light




I also found 120vac version that uses 3.5 watts..
48 SMD 3528 LED E27 LED Light Bulb - Household LED Lights - LEDLight

I guess I will start looking for lamp bases with the GX5.3 two prong system, since it seems like that is the preferred choice for building LED bulbs.

My guess as to about 40W incandescent equivalent seems to be about right for the three 1W Star LEDs that I am using. The good thing about the LEDs is that you can focus them easily. 40W focuses down on a workbench to a 3' by 3' area which is bright enough to read and do fine electronics work (look at small parts). This is with 5 degree lenses on the LEDs, although I would probably buy 30d lenses next time.

I think my cost for a three 1W LED system that I then need to put together is about $15, maybe a bit more because I didn't count wire and solder. It would be well worth it to buy premade bulbs with the same output for $20.

I am still waiting on the 3W Stars. I also have some supercapacitors on the way, enough for a 12V system. I'm not sure what I am going to do with them yet, but I will probably experiment and see if they charge up like a battery. Ideally they would be used to hold braking regeneration power on an electric bike but I don't have a functioning ebike at this time. I am thinking to try out a solar powered LED light with no batteries, and see how long the supercaps hold a charge.

I'm going to look more at those little 12v arrays they make to replace lamps in cars.
Those might be more tolerant to my solar chargers..

I'm not up to speed on supercaps, but I know that a 1 Farad capacitor can provide
(or store) 1 amp at 1 volt (1 watt) of power.
So, a 1 Farad flashlight can provide 100 ma @ 1v for 10 seconds.. Or 50ma for 20 sec.. etc.

It sure seems like rechargeable batteries are the best way to go..

Now that's funny.
I am in the same boat. 1 post to go.

I did some testing on Cree 1W Warm White Star LED's to see if they would work within the range of a 12V lead acid battery system, with 4 Star LEDs in series using no voltage regulator.

12V lead acid battery voltage range:

Min: 50% discharge at 67F: 12.61V
12.61V / 4 LEDs = 3.15 V across each LED

Max: Maximum recommended charging rate: 14.4V
14.4V / 4 LEDs = 3.6V across each LED

Note that there may be an inrush current when the LEDs are switched on, this does not take inrush current into account.

Voltage range for each LED: 3.15V - 3.60V

I did some testing using 2 LEDs in series, setting the Voltage using a V regulator, and measuring A. The single LED V is one half of the measured V. Note that amps should be the same for a single LED.

Voltage - single LED V - measured A
7.35V - 3.68V - 0.43A
7.23V - 3.61V - 0.40A
7.21V - 3.60V - 0.38A
7.10V - 3.55V - 0.35A
7.03V - 3.52V - 0.34A
6.84V - 3.42V - 0.30A light still bright
6.71V - 3.36V - 0.26A
6.48V - 3.24V - 0.21A
6.32V - 3.16V - 0.19A
6.24V - 3.12V - 0.17A light still relatively bright
6.04V - 3.02V - 0.12A light still usable though not as bright
5.72V - 2.86V - 0.06A
5.41V - 2.70V - 0.03A
5.18V - 2.59V - 0.01A
4.94V - 2.47V - 0.00A light appears, very dim

At the battery system max, 3.6V across one LED, the measured current is 0.38A, which is higher than specified at 0.35A. Brightness is very bright.

At the battery system min, 3.15V across one LED, the measured current is 0.19A, and brightness is satisfactory.

Ideally, at battery system max (3.6V per LED) current should be the rated current (0.35A), which would indicate a resistance of 3.6V / 0.35A = 10.3 ohms.

A four LED in series system shows 0.38A at 3.6V, or a resistance of 3.6V / 0.38A = 9.5 ohms.

Adding a 1 ohm resistor in series would reduce that amperage at battery system max to just under the rated 0.35A. 3.6V / 10.5 ohms = 0.34A

It might provide some protection against inrush current when switched on.

It would diminish the amperage at the battery system min as follows:
3.15V / 10.5 ohms = 0.30A

At 0.30A the light was still bright.

Each LED needs 1 ohm. With 4 LEDs, 4 ohms are needed.

So with a 12V lead acid battery system, I would recommend using 4 Cree 1W Warm White Star LEDs in series with a 4 ohm resistor, 1W or better, in series. NO REGULATOR IS NEEDED.

Here is a cheaper source for Star LEDs:

1W High Power LED Warm White Star Emitter 80-90LM [ST-1WWW] - US$0.98 : SatisLED Store, China LED wholesaler

http://cruisenews.net/whaleback/22I2011/1.jpg

http://cruisenews.net/whaleback/22I2011/2.jpg

http://cruisenews.net/whaleback/22I2011/3.jpg

http://cruisenews.net/whaleback/22I2011/4.jpg

http://cruisenews.net/whaleback/22I2011/5.jpg

I am making some cheap LED lights for a boat project. I purchased 1000 warm white 5mm LEDs for $65, taking advantage of a quantity discount.

This project will use an incredibly high tech and innovative system of voltage regulation: I am using old batteries that previously were used for an electric bicycle and are pretty much worn out. The batteries do not allow the voltage above about 12.8V. So a series of 4 LEDs needs no regulation at all. The batteries do not have the capacity that they used to have, but I am now pulling less than an amp where the electric bike used to pull close to 20 amps, maybe more on startup.

The 20 LED lights will pull about 0.1 amp, since each 4-series pulls 20 ma. The 32 LED light will pull about 0.16 amp. In practice, actual amperage changes quite a bit with voltage. This has the happy situation that as battery voltage drops, amperage drops so the battery will last longer. Yes, the light output drops but it is still usable even at lower voltages.

My battery system has a 10W solar panel with charge controller. I never expect to add an alternator to the system, which means it is fairly sure that that there will never be voltage spikes.

The LEDs are rated 3.0V to 3.4V. Four in series would be rated at 13.2V. I don't expect my old batteries to allow the voltage to rise above 13V, even under charge from the solar panel.

Very cool. Does that one panel put out much light?

For the small space in my decked sailing canoe, it is enough light, but the floor is only about 3 feet from the lights. In a larger room in a house, it would be a little more than a kerosene lamp, but less than a 40W bulb.

http://cruisenews.net/whaleback/24I2011/1.jpg
with flash, no light - batteries are up front, tied down under the boards
http://cruisenews.net/whaleback/24I2011/2.jpg
with flash, light on
http://cruisenews.net/whaleback/24I2011/3.jpg
without flash
http://cruisenews.net/whaleback/24I2011/4.jpg

http://cruisenews.net/whaleback/24I2011/5.jpg

http://cruisenews.net/whaleback/24I2011/6.jpg

http://cruisenews.net/whaleback/24I2011/7.jpg

http://cruisenews.net/whaleback/24I2011/8.jpg
Solar controller and positive buss bar
http://cruisenews.net/whaleback/24I2011/9.jpg

http://cruisenews.net/whaleback/24I2011/10.jpg
Negative buss bar and rats nest, needs to be cleaned up.

I got the LEDs for about $65 for 1000 pcs. There are 20 LEDs in each of the arrays, so one array costs about $1.30 for LEDs, plus some scrap plexiglass, some solder and a couple of pieces of wire.

To get the equivalent of a 40W bulb, my guess is that you would need an array with 40 LEDs, which would cost $2.60 and would use about 0.2 amps.

The strategy with LEDs is to put the lights so they shine right where you need them, and have enough different lights so there is always one light that lights up exactly what you want it to. That way you don't need to light all the lights, you can conserve power by lighting up that area you are using. And if you want to light up the whole house for some reason, you could do that too by turning them all on.

Looks like plenty of light for the application.

Watch out for cheap LEDs
 

LEDs are easily damaged by overheating and the cheaper ones tend to fade much sooner than high quality name brand ones. So for long operating time lighting I would recommend using high quality LEDs. Good luck! :)

Haven't heard of them. Last I checked LEDs were slightly less efficient than fluorescent lights.

There are a lot of inefficient LEDs. But, there are some very efficient ones out there to the tune of 100 lumens per watt. CLFs are around 60-70 I believe. However, these LEDs aren't cheap at all, but they are being used for things like street lamps, parking structures, etc. Unfortunately, I don't know of any high end LEDs for home use.

Home LED's are getting lower prices, and some are close to 50-60 lumens per watt. Lumens though are not all the same -- LED's are focused light, and CFL's depend on the fixture for focus (or not). LED's last longer in general, at least theoretically, and some are now dimmable; as are a fair number of CFL's.

Color temperature is the big breakthrough on LED's (and for CFL's a while ago) -- look for 2700K to 3000K for light that is virtually indistinguishable from incandescent bulbs. Some incandescents are too red, in my opinion.