LED Stars and hearts

Discussion in 'The Projects Forum' started by j_thain, Feb 19, 2010.

  1. j_thain

    Thread Starter New Member

    Nov 9, 2009
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    hi there all
    you may remember me as i had a project back last year for a LED moving wheel.
    thanks eveyone who provided information it was a great help and an excellent finished project

    no i need to help make a costume

    they want 2 stars and one heart
    each star will have 24 LED's and the heard will have 22 LED's

    the stars need to be white and the heart needs to be red

    what is the best way to wire it so each star and the heart can be turned on one at the time and for it to be concealed in a costume. it would be great if they could be run of a 9v battery or two.

    also i have found some cheep LED's on ebay but not too sure if they would be ok...
    this is the spec of the LED's
    • Case Style: Round 3mm
    • Millicandela Rating (Typical): 10000mcd
    • Voltage Rating: 3.2-3.8V
    • Forward Current: 30mA
    • View Angle: 25deg
    • Life Rating: 100,000 hours

    any suggestions would be greatly appreciated

    james
     
  2. Wendy

    Moderator

    Mar 24, 2008
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  3. Audioguru

    New Member

    Dec 20, 2007
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    25 degrees is a very narrow viewing angle. You might not see the LEDs unless they are pointing directly at you. Get LEDs that have a viewing angle of 90 degrees or more.

    The LEDs in my solar garden lights have a viewing angle of 140 degrees.
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
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    I believe for costumes, EL Wire is a very effective solution. You can get the colors you need and at $17us(shipping included) for 4 feet, you cant beat it. It looks like those glow-in-the-dark necklaces (but brighter) and you can shape them into stars, hearts, letters, numbers, ect..

    They come ready to go. Works off 2 AA batteries and no heat. Very good very costumes. They have White and Red.
    http://www.ravestuff.com/collections/el-wires?gclid=CNiF45zU_58CFSJ25QodaTgLlQ
     
  5. j_thain

    Thread Starter New Member

    Nov 9, 2009
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    i have read through some of the articles and its not making any sense to me!

    not sure if anyone can explain it in simple terms

    i have purchased the LED

    i have got these ones

    WHITE
    Lenses Type : Crystal Clear
    Case Style : Round 3mm
    Brightness : 10000mcd (Ultra Bright)
    Forward Voltage : 3.2v – 3.8v
    Forward Current : 20mA (Typical) 30mA (Max)

    RED
    Lenses Type : Crystal Clear
    Case Style : Round 5mm
    Brightness : 8000mcd (Ultra Bright)
    Forward Voltage : 1.8v – 2.2v
    Forward Current : 20mA (Typical) 30mA (Max)

    i was hoping to run them off 2 or 3 9v batteries and have a seprerate switch to turn each star and the heart on!

    thanks
    james
     
  6. retched

    AAC Fanatic!

    Dec 5, 2009
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    How many LEDs are is a star and how many in a heart?

    How long were you hoping to have the batteries last?
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    What's the problem? We'll try to help where we can.

    A suggestion, think how you would lay out these LEDs to get the desired effect.
     
  8. j_thain

    Thread Starter New Member

    Nov 9, 2009
    15
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    the layout....
    i was hoping to run them in series. as three different circuity going from one side of a 9v battery to a switch them to each led in series and back to the battery. i'm sure there may be some missing components to make this work.

    the batteries dont have to last that long as the song they are used for only last 3 mins so we can change the batteries each night it is used.

    there are 2 stars and one heart

    24 leds per star and 22 leds for the heart

    thanks so much for your help
     
  9. Audioguru

    New Member

    Dec 20, 2007
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    A 9V battery will drop to 6V as it is used so you cannot connect two 3.5V white LEDs in series and in series with a current-limiting resistor. Each white LED needs its own current-limiting resistor.

    Connect two 2.0V LEDs in series and in series with a current-limiting resistor.

    if the LEDs each have a current of 5mA then they will still be seen. The current for each white star is 120mA. The current for the red heart is only 55mA so their current can be 10mA each.

    Here is a voltage graph of a 9V alkaline battery with a load of 150mA. Your LEDs will be fairly dim in 1 hour and dead in about 2.5 hours.
     
  10. j_thain

    Thread Starter New Member

    Nov 9, 2009
    15
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    sorry you have kinda lost me a little
    i understood some of it i think

    so how would you recommend connecting the leds to the battery and switch and what other stuff do i need?
     
  11. Audioguru

    New Member

    Dec 20, 2007
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    1) Each white LED needs is own current-limiting resistor. The battery is 9V when new and the white LEDs average 3.5V each. Ohm's Law calculates the resistor to be (9V - 3.V)/5mA= 1100 ohms. Use 1k ohms/quarter Watt resistor for a current of 5.5mA.

    2) Two red LEDs are connected in series and in series with a current-limiting resistor. The resistor calculates at 500 ohms. Use 470 ohms/quarter Watt resistor for each series pair of red LEDs.

    3) If you don't know how to connect the battery and switches then you should do gardening instead of making this very simple electric project.
     
  12. j_thain

    Thread Starter New Member

    Nov 9, 2009
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    take a look at this for the red heart
    is this right?
    what resistors will i need?[​IMG]
     
  13. j_thain

    Thread Starter New Member

    Nov 9, 2009
    15
    0
    i just got your last message while sending mine
    perfect
    i think i got it know
    i will let you know how i get along

    if all else fails i will take your advice and go to gardening lol

    thanks so much for your patience
    james
     
  14. Audioguru

    New Member

    Dec 20, 2007
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    A new 9V alkaline battery will power 24 white LEDs at 5mA or 22 red LEDs at 10mA for about 1 hour when they will look dim.
    Use a rechargeable 9V Ni-MH battery.
     
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