LED light testimonial

Discussion in 'Homesteading Questions' started by BCR, Jan 16, 2005.

  1. BCR

    BCR Well-Known Member

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    Back in early November I grabbed my little Princeton Tec one LED clip light I got at Campmor for just under $6 to put in my pocket to use later that night when crossing a street. The plan was to let cars know I was crossing this busy foot-traffic/car traffic area. Well, one thing led to another, and it IS small and I had it off the clip, and in taking the dogs out I lost it. I spent 5 minutes looking for it then made the decision to use the larger car flashlight I had and went on my way. Looked inside and out for it the next day. No luck.

    Last night my SO said, "hey, its been so warm out I meant to tell you about a glow-worm that came out. Seems to be the only one." Well, when we walked down the sidewalk she said "there it is". I saw it and then dug down in the grass and found my little light buried in the grass/mud and on. We must have stepped on it and turned it on in the last few days.

    Now, we have had MANY INCHES of rain since I lost this thing. I brought it in, opened the back, took the batteries out, let them dry over night, put it back together and it is working like a charm. Its safely back on its clip and in my waist pack where it belongs. What a great product to survive 2 months outside in wind, rain and many freezing nights.

    They are still available at Campmor.com
     
  2. gobug

    gobug Well-Known Member Supporter

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    As an exterminator, I have a flashlight fetish. I have tried just about every brand and style on the market. I have one that will almost cause retina damage and its just a little bigger than my index finger. The problem with this light is the battery costs $11 and it wears out in a week of use on my job.

    My favorite of all time is the LED flashlight I bought at Costco. I paid $18 for 2 in a package. It takes a single AA battery and it lasts more than six months. While it won't light up the side of the house, it works great under sinks and such.
     

  3. Thumper/inOkla.

    Thumper/inOkla. Well-Known Member

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    I have a LED headlamp that I use everynight, I love it and would have a hard time doing chores without it.
     
  4. Mr. Dot

    Mr. Dot Well-Known Member

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    What Thumper/inOkla. said.
     
  5. Lisa in WA

    Lisa in WA Formerly LisainN.Idaho Supporter

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    Since we are on solar power we use LED Christmas tree lights. They are so pretty and use almost no power. They are also guaranteed not to burn out for something like 20 years. I wish more things were made with them.
     
  6. doigle

    doigle Well-Known Member

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    Wow, where did you buy LED Christmas lights? I've seen them on municipal trees, but didn't know they were available and affordable to the huddled masses.
     
  7. BCR

    BCR Well-Known Member

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  8. BobBoyce

    BobBoyce Well-Known Member

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  9. Lisa in WA

    Lisa in WA Formerly LisainN.Idaho Supporter

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    My lights are by Forever Bright: www.foreverbright.com
    I found some at Lowes, some at Backwoods Solar. The best price was at Albertson's 2 years ago. 5.99 for a 100 light string. The web site lists retailers.
     
  10. Cosmic

    Cosmic Well-Known Member

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    You can just build any LED light thingee yourself. The circuits are pretty simple.

    http://www.otherpower.com/otherpower_lighting_leds.html

    Basically you need a LED, resistor and battery for the most simple. Good places to get very cheap LED's are:

    http://www.goldmine-elec.com

    http://www.allelectronics.com

    The best deals are typically the assortment groups. I have drawers full of the critters. Those big jumbo ultrabrite whites can be blinding. With a few chips can build some fancy flashing circuits for Xmas trees, etc. The nice ones are done in ceramics and the bulbs are LED's.
     
  11. mightybooboo

    mightybooboo Well-Known Member

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    Anybody used the 110volt edison base, 9-13 LED bulbs sold on ebay?

    BooBoo
     
  12. BobBoyce

    BobBoyce Well-Known Member

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    Sorry to say, but those 120 volt LED lights sold on eBay are not the best for efficiency. While they are better than some of the alternatives, using less than the ideal number of LEDs for your operating voltage results in higher waste energy loss in the resistor(s).

    Unless you maximize the number of LEDs to take advantage of most of the voltage (by stringing in series) at the required current draw, the resistor has to "waste" the rest of that wattage that the LEDs can't use. Most of those holiday LED strings (35 or 70 LED or similar) are way more efficient since they utilize more of the wattage for light output than heat wasted in resistance.

    I published a small LED lighting guide a few months back on another site, let me go grab that and post it after this message, it's kind of lengthy. It gives some examples for typical ultra bright white LEDs, and some simple math to calculate losses for a couple of given setups.

    Bob
     
  13. BobBoyce

    BobBoyce Well-Known Member

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    This was a response to a discussion on most efficient use of alternative energy (solar, wind, microhydro, ect) for white LED lighting.

    Exact LED voltage and current vequirements vary based on the LED used. LED color is a good indicator of the LED chemistry, hence the normal operating voltage of the LED. Limiting current is important if you want your LEDs to last. Most LEDs are rated at 20 mA but will put out more light (and heat) at higher currents than rated, but at a tradeoff of lowering the lifespan of the device.

    Please keep in mind that the following is an example, and may or may not apply for the type of white LEDs that you may have. I have used the following with very good results with all of my low voltage white LED lighting projects. This may be applied to higher voltages by observing your LED specs and following the math. By using the standard resistor value closest to the actual value needed, you should still fall well within spec on the LEDs.

    -------------------------------------------------------------------

    We will use a circuit voltage of 12.5 VDC, typical resting voltage of a 12 volt lead acid battery.

    Say we want to run a single LED that requires 20 mA at 4 VDC off of 12.5 VDC. A series resistor is added to limit current to 20 mA, which provides the 8.5 V of voltage drop required.

    Power Used by LED I .02 Amperes X E 4.0 Volts = P .08 Watts
    Power Dissipated by Resistor I .02 Amperes X E 8.5 Volts = P .17 Watts R= 425 ohms
    -------------------------------------------------------------------------------------------
    Power Used Total I .02 Amperes X E 12.5 Volts = P .25 Watts

    In this example, the LED is consuming .08 watts, and the resistor is dissipating .17 watts, so electrical power consumed by the LED is only 32% of the total power consumed. 68% of the power is wasted in the resistor, not very efficient.



    Now say we want to run two LEDs in series that requires 20 mA at 4 VDC each off of 12.5 VDC. A series resistor is again added to limit current to 20 mA, which provides the 4.5 V of voltage drop required.

    Power Used by LED1 I .02 Amperes X E 4.0 Volts = P .08 Watts
    Power Used by LED2 I .02 Amperes X E 4.0 Volts = P .08 Watts
    Power Dissipated by Resistor I .02 Amperes X E 4.5 Volts = P .09 Watts R= 225 ohms
    -------------------------------------------------------------------------------------------
    Power Used Total I .02 Amperes X E 12.5 Volts = P .25 Watts

    In this example, the LEDs are each consuming .08 watts, and the resistor is dissipating .09 watts, so electrical power consumed by the LEDs is 64% of the total power consumed. 36% of the power is wasted in the resistor. Light output is doubled for the same total power consumption when compared to the single LED. Better efficiency.



    Now say we want to run three LEDs in series that requires 20 mA at 4 VDC each off of 12.5 VDC. A series resistor is again added to limit current to 20 mA, which provides the 0.5 V of voltage drop required.

    Power Used by LED1 I .02 Amperes X E 4.0 Volts = P .08 Watts
    Power Used by LED2 I .02 Amperes X E 4.0 Volts = P .08 Watts
    Power Used by LED3 I .02 Amperes X E 4.0 Volts = P .08 Watts
    Power Dissipated by Resistor I .02 Amperes X E 0.5 Volts = P .01 Watts R= 25 ohms
    -------------------------------------------------------------------------------------------
    Power Used Total I .02 Amperes X E 12.5 Volts = P .25 Watts

    In this example, the LEDs are each consuming .08 watts, and the resistor is dissipating .01 watts, so electrical power consumed by the LEDs is up to 96% of the total power consumed. Only 4% is wasted in the resistor. Light output is tripled for the same power consumption when compared to the single LED. Best efficiency.

    These calculations were done with P = I * E where
    P = (power in watts)
    I = (current in amperes)
    E = (volts)

    Resistance values can be calculated with ohms law E = I * R where
    E = (volts)
    I = (current in amperes)
    R = (resistance)

    For this we use the variant R = E / I
    -------------------------------------------------------------------

    I should also mention, if you are rely on an alternative power source with a battery bank, your intention is to maximize efficiency, and you are intending to run LED lighting, it is better to run your LED lighting directly from your battery bank power than from an inverter. Many times inverter losses alone will be more than your total lighting current requirement with LED lighting.

    If you are on grid-power (120 Volts AC) and just wish to reduce lighting power consumption, consider parallel pairs of series strings run in opposite polarities. Since the series LED strings each only light and use power from one half of each AC cycle, using paralleled but opposite polarity sets of series strings will give twice the available light for each cycle of AC power. With identical holiday LED strings, to accomplish this, just swap the direction the plugs are plugged into the outlet. For polarized plugs this requires filing or trimming the wider blade so the plug can be reversed. Many holiday strings do not use polarized plugs however.

    I hope this information proves to be useful.
    Bob
     
  14. Ed Norman

    Ed Norman Well-Known Member

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    Thanks Bob. I have a sheep camp with 4 light fixtures. Each one has two bulbs, the 12VDC kind with two pegs sticking out the sides. Stick it in the holder and twist half a turn to secure. Using your third example, could I wire three LEDs into a broken bulb and use them without a resistor? I know the life would be cut down, but it looks like 3 bulbs in your example with no resistor is pretty close to being perfect.
     
  15. BobBoyce

    BobBoyce Well-Known Member

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    Yes Ed, if your supply voltage is right at 12 VDC it should work just fine. Where you would have to worry is if the voltage rises above 12 by much, as in automotive systems with the engine running, or alternative energy sources that are not regulated or connected via a charge controller.

    The usual max rating on white LEDs is 4.5 VDC, so 3 in series can survive up to 13.5 VDC. Without a series resistor to limit current, it could permanently damage the LEDs if the voltage were to exceed that, even for a short time. If you wanted to be on the safe side, you can add a 22 or 27 ohm 1/4 watt resistor in series with the LEDs.

    Bob
     
  16. Cosmic

    Cosmic Well-Known Member

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    If you are building a LED network and worried about overvoltage just stick a zener in parallel of the proper voltage rating to limit any rise above the value to be protected.
     
  17. mightybooboo

    mightybooboo Well-Known Member

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    I took a string of red berry LEDS,15 total hooked up to 2 C-cell alkaline batteries .Turned it on wednesday at 5pm,they are still bright.Will let you know when the lights go out.Must say so far Im very impressed with the power consumption.While the bulbs are quite bright,the area they actually light isnt much.Can barely feel any heat on them.

    BooBoo
     
  18. mightybooboo

    mightybooboo Well-Known Member

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    Bob Boyce,
    I can see the power use might be poor,more interested in how they perform both light output and longevity wise.I myself am more interested in the direct 12 volt hookup,ie,an RV type setup and solar setup.
    Any use along those lines with commercially available products would be most helpful.I will look into some white light strings of 12 volt if I can find them to play around with.

    BooBoo