Help powering 10 RBG Leds

Discussion in 'The Projects Forum' started by larry502, Feb 8, 2013.

  1. larry502

    Thread Starter New Member

    Feb 8, 2013
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    Hello everybody!

    I working on a project and I need to power 10-15 slow fade leds. I would like to be able to use a iphone battery or maybe a similar cell phone battery as i need to keep the size a small a possible. And having the option to charge the battery would be a huge plus.

    Right now when i hook them up to 2x AA batteries i can only get 2 leds to light up.. when i use 3 leds it wont change colors and the light is really dim.

    Below is the specs of the lights im working with.

    Thanks In Advance for any and all help!!!!!!



    Size: 5mm
    Lens Color: Water Clear
    Reverse Current (uA): <=30
    Life Rating: 100,000 Hours
    Viewing Angle: 20 ~ 25 Degrees
    Absolute Maximum Ratings (Ta=25°C)
    Max Power Dissipation: 80mw
    Max Continuous Forward Current: 24mA
    Max Peak Forward Current: 75mA
    Reverse Voltage: 5~6V
    Lead Soldering Temperature: 240°C (<5Sec)
    Operating Temperature Range: -25°C ~ +85°C
    Preservative Temperature Range: -30°C ~ +100°C
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    Your spec's do not say the most important info:
    HOW MUCH VOLTAGE DO THEY NEED??
    Do the LEDs limit their current to less than 24mA or must YOU limit the current??

    Maybe your AA batteries are throw away alkaline type. Then two in series are 3V only then they are brand new and if the load current is not high. But blue and bright green LEDs need at least 3.4V.

    You connected two LEDs to the two batteries but probably did not limit the current so they drained the batteries. Then you connected 3 LEDs without limiting the current and they completely killed the batteries.

    A cell phone battery is 4.2V when fully charged and is 3.2V when the protection circuit in the battery disconnects it. The charger circuit is inside the phone but you don't have it. So if you simply apply power to the battery then it might disconnect or catch on fire.
     
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  3. larry502

    Thread Starter New Member

    Feb 8, 2013
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    Is there a smaller type of battery i could use? I don't know much about batteries. AA don't really work as they are way to big for the project im doing.

    I really appreciate your help and feedback!!
     
  4. takao21203

    Distinguished Member

    Apr 28, 2012
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    You need one of my joultheif PCBs.

    They are current limited so they won't burn LEDs. But the more input voltage, the more output voltage.

    Originally designed to light up 6V LEDs from 5V. But they can indeed power all sorts of LEDs. Efficiency is not so good, 60 to 70% at best.

    If you need something better, use a voltage booster chip. Many of them are not current limited however.

    Lighting 15 LEDs from a small battery is not so easy to do with good efficieny. All in series, you need about 40 volts or something. Even a good converter will drain a lot of current from a small battery.

    One solution is to use lower currents and resistors. Maybe not what you want. If you want to use them at full current, you need a larger battery pack.

    Battery size and hours of operation will correlate.
     
  5. larry502

    Thread Starter New Member

    Feb 8, 2013
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    I would be more then happy buying something that would power 10-15 but it seems like your device is more suited more 1 led. maybe im wrong.

    Im trying to fit everything into a hat.

    I have placed leds in side of the hat bill and would like them to work via battery and not my adriuno using it as a power source.

    I have ws2801 lights on the inside of the bill.

    The whole hat is made with a 3d image and went hit with different colors makes the image inside the hat move and change. it's really hard to explain so i will take some videos to show you guys.
     
  6. larry502

    Thread Starter New Member

    Feb 8, 2013
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    look up jumbie art to see the art im taking about. This is my close friend he does all the art.
     
  7. Audioguru

    New Member

    Dec 20, 2007
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    The art and colors changing are COOL!
    I wish my computer can show the 3D effect.

    I don't think I ever wore a hat in my entire life.
     
  8. larry502

    Thread Starter New Member

    Feb 8, 2013
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    It's hard to capture with a video camera in person it's mindblowing. Im not a huge hat person but its easily to understand the appeal of the lights with the hat.

    I was thinking of trying some BR2030 batteries ... as it was suggested by a friend... Anyone else have any ideals on what direction i could take.
     
  9. larry502

    Thread Starter New Member

    Feb 8, 2013
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  10. Audioguru

    New Member

    Dec 20, 2007
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    A tiny battery can produce a very low current for a little while.
    The video shows some LEDs IN THE DARK!
    My nose lights up like that in the dark when I simply have one of those tiny batteries under my tongue.

    I made some LED chasers. They use 2 AA alkaline cells for ones with red LEDs or use 4 cells for ones with blue LEDs. They are very bright when the batteries are new but slowly get dimmer and dimmer and dimmer and dimmer until they can barely be seen in the dark but the electronics is still working fine. The AA cells drop to about 0.75V each when I replace them after running for about 6 months continuously.

    You are talking about a tiny CR2030 battery cell. Energizer doesn't make it but their website has the datasheet for the CR2032 lithium coin cell which is a little bigger with a slightly higher capacity. It is rated for 240mAh when its 3V drops to 2V and its load is 15k ohms (only 0.2mA). It can supply a few 2 seconds duration 6.8mA pulses. Then it will not light LEDs long.
     
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  11. larry502

    Thread Starter New Member

    Feb 8, 2013
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    I was able to find a little more info on the lights.

    Power with 3-3.4VDC
    Current draw: 10-20mA depending on voltage and displayed color

    Still running in circles trying to figure out a battery that would work. This is so much easier running 12v.
     
  12. Audioguru

    New Member

    Dec 20, 2007
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    Then you need at least 3.4V. They say Current Draw so I assume the LEDs limit their own current with their fading circuit. They do not say if the LEDs can be connected in series to use 12V.

    Here is the simple math:
    1) 15 LEDs at 10mA each= 150mA.
    2) Forget about a tiny battery, a cell phone lithium rechargeable battery will be fine and will power 15 LEDs for about 4 or 5 hours. Connect the LEDs in parallel.

    First try only one LED. If it burns out then you must limit the current to each LED.
     
  13. bertus

    Administrator

    Apr 5, 2008
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  14. Audioguru

    New Member

    Dec 20, 2007
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    Larry is using slow fade leds that have built-in fading circuits and they "draw" 10-20mA so they might have current-limiting built into the fading circuit.
    Bill's articles do not talk about them. He talks about only ordinary LEDs.

    Here is a link to "slow fade LEDs" that have exactly the same spec's as the LEDs used by Larry: http://www.adafruit.com/products/679
    They do not have a datasheet so nobody knows if they have built-in current-limiting.
     
  15. larry502

    Thread Starter New Member

    Feb 8, 2013
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