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LEDs powered from AAA battery

Discussion in 'LEDs and Optoelectronics' started by dorabud, Jan 30, 2018.

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  1. dorabud

    dorabud

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    Jan 30, 2018
    I have an idea on a project that involves LED Lights and I know nothing about LED s. I would like to use 3 small clear LED lights that can be lit from a single AAA Battery, is this possible?
     
  2. kellys_eye

    kellys_eye

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    Jun 25, 2010
    Possibly. LEDs require anywhere from 1.2V to 3.6V (colour-dependent) so what LEDs are you using? If you can give a part number we can check the datasheets and see what the manufacturers say.
     
  3. dorabud

    dorabud

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    Jan 30, 2018
    Don't know what lights to get, I haven't got that far.
     
  4. BobK

    BobK

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    You would most likely need some kind of boost converter to run them off a single AAA. Look up "Joule thief".

    You can run them without a converter from a CR2032 coin cell, which is 3V.

    Bob
     
    Merlin3189 likes this.
  5. dorabud

    dorabud

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    Jan 30, 2018
    what does a joule thief do?
    I am a welder by trade
     
  6. BobK

    BobK

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    Jan 5, 2010
    It boosts the voltage from a 1.5V cell to enough to run LEDs.

    Most LEDs require about 2V or more.

    Bob
     
  7. Audioguru

    Audioguru

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    Sep 24, 2016
    A Joule thief boosts the voltage of a "run down and almost dead" single battery cell to dimly light a 3V LED.
    I have many solar garden lights that use an AA or AAA rechargeable cell and a voltage boosting circuit.

    An AAA alkaline cell averages 1.2V during a discharge and has a capacity of 800mAh for Energizer or 850mAh for Duracell. Then it can provide 1.2V x 825mAh= 1 Watt for 1 hour.
    An LED is fairly bright with a current of 20mA. Three 3V LEDs need a power of 3 x 3V x 20mA= 0.18W but the voltage boosting circuit needs about 0.1W so the total is 0.28W. An AAA alkaline cell will power them for 1W/0.28W= 3.6 hours.
     
  8. dorabud

    dorabud

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    Jan 30, 2018
    Is it possible to stack 357/303 coin cell battery to do the job. I have limited space and a joule thief looks like it may not fit in the area available
     
  9. Audioguru

    Audioguru

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    Sep 24, 2016
    The datasheet for a tiny 357 button battery cell (or a bunch of them in series) says it is designed for a load of only 0.2mA which is about 1/300th of what you need. It has a capacity of 138mAh at its tiny current but an AAA cell has a capacity of 825mAh at the much higher 180mA of current you will need.
     
  10. BobK

    BobK

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    Jan 5, 2010
    What do you expect to do with these three ligths. Are they expected to give out significant light (like a flashlight) or just be visible (like an On indicator?)

    If the latter, under what lightng conditions? For normal indoor lihting, a modern high-efficiency LED can be run at 1 mA.

    Bob
     
  11. dorabud

    dorabud

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    Jan 30, 2018
    The area these lights are to used is normally unlighted but sometimes a light is required to make sure a part is in location, we use a small flash light now. I have 3 holes (about 1/4in Dia and on a 3" bolt center circle) through the punch that the lights can be placed. Normally lights are not required the light will give the operator a little better hands free check. The Area that I have to place the Battery and things is W3/4in x H5/8in x L2 3/8in the switch will mounted in an area about 6" away. this would be a normally off switch. The purpose for the lights is to free up the operator hands for safer operation. The lights will only be on for about 2 to 3 minutes at a time.
     
  12. dorabud

    dorabud

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    Jan 30, 2018
    If I changed to a 9 volt battery would that help?
     
  13. BobK

    BobK

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    Jan 5, 2010
    OK, so you do probably want something like 20mA for each LED.
    And you presumably want white, which require over 3V.

    I would go with a small LiPo battery like these:

    Small LiPo battery

    I am using these same batteries for some LED strips and I am very happy with them.
    And they are rechargeable.

    These would run 3 LEDs at 20mA each for about 6 hours before needing recharging.

    Bob
     
  14. Audioguru

    Audioguru

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    Sep 24, 2016
    You also need a charger for the battery. Maybe buy a quadcopter and use its charger.
    A name brand 9V alkaline battery will power two LEDs in series plus a third LED by itself for about 15 hours. Current limiting resistors are needed.
     
  15. BobK

    BobK

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    Jan 5, 2010
  16. dorabud

    dorabud

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    Jan 30, 2018
    Check my wiring, Battery - to light1, light 1 to light 2, light 2 to light 3, light 3 to switch, switch to Battery +, Completed?
     
  17. dorabud

    dorabud

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    Jan 30, 2018
    going to order the part that you suggested, is there anything else that I might need and thanks for all the help,
     
  18. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    You need a resistor (or multiple resistors, depending on how you wire the LEDs) to limit the current through them.

    LEDs are not like light bulbs.

    In our resources section we have a resource about LEDs. Sections 1 and 2 would be the most relevant to what you're doing I think.
     
  19. dorabud

    dorabud

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    Jan 30, 2018
    Please be patience this is way above me. Now that I have the battery and the LEDs, I also need resistors?
    How do I determine the correct resistor? Thanks you for the read but I'm still a slow on this hole thing, and may have to read this a couple of times.
     
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