Wiring 100 LED lamps safely but as bright as possible using 9 Volt batteries

Discussion in 'General Electronics Chat' started by Atef94, Aug 23, 2015.

  1. Atef94

    Thread Starter New Member

    Aug 23, 2015
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    Hi everyone thanks for reading my thread :) I have 100 LED lamp ( the big ones not the regular 5 mm type ) I need to wire those all in one circuit and providing them current from one or two 9 v battery ( as needed ) I'm asking for a way to do it .. Questions I'm having in mind: Should I sold a resistor to every LED or just one next to the battery .. Should I just ingore resistors and sold them in two parralel groups ..
    Any help would be appreciated :) If anyone is experienced anough to give me a way to wire them and resistor value to use :D
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    What are the manufacturer and part number for the LED, or what is the forward voltage (Vf) and what curret do you want to run through them? Also, how long do you want the LEDs to light? I doubt that two 9 V batteries have enough power to do what you want, but there is no way to know for sure without the specifications for the LED.

    ak
     
  3. Atef94

    Thread Starter New Member

    Aug 23, 2015
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    I dont know the specifications :/ in my country sellers dont know a thing about their product .. However i operated the blue ones 40 one on a 9v battery
     
  4. Atef94

    Thread Starter New Member

    Aug 23, 2015
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  5. Sensacell

    Well-Known Member

    Jun 19, 2012
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    A 9 volt battery has very limited current capacity, (high internal resistance) lighting 100 LED's on one 9V battery is possible if the current is very low, but you are not going to get much in terms of brightness or battery life.
     
  6. KJ6EAD

    Senior Member

    Apr 30, 2011
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    Those look like 8mm LEDs so they are the same 20mA die as 3mm or 5mm LEDs but in a bigger blob of epoxy.
     
  7. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    A typical PP3 battery may last a few minutes with this kind of load; does that suit your requirements?
     
  8. TheButtonThief

    Active Member

    Feb 26, 2011
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    If they MUST be battery powered, you may want to consider a 12V SLA battery (though they are expensive) or a "battery pack" of around 8 or more AA's

    Also, you need to consider the cable diameter you use to wire them all up. 100 of those LED's are likely to draw at least 2A so use at least 3mm²
     
  9. Atef94

    Thread Starter New Member

    Aug 23, 2015
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    I can use two 9v together no problem if these leds wont be damaged :) so I wont need any resistors?
     
  10. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    At least 3mm², are you sure?
     
  11. Atef94

    Thread Starter New Member

    Aug 23, 2015
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    Guys this is what i have in mind now .. I wire every 50 led in parallel then those two groups in serie with a 9v and a 4,5 v together :) would that work ?? ( 13.5 v total )
     
  12. TheButtonThief

    Active Member

    Feb 26, 2011
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    A 9V PP3 battery typically has a 250mA current capacity, really not that much. 2 PP3's in parallel will give you about 0.5A, still not that much considering your load will be over 2A. The batteries will last about 15 minutes before the LED's start to dim and they'll be completely dead after about 20-25(max) minutes.

    Consider AA's, wire 6 together is series to get 9V and use rechargeables (as they have a high current capacity, up to 3.5A each).

    Or, you'd be better off connecting 6 AA's as 3 groups of 2 to give a lower supply voltage of 3V but a higher current capacity of 10.5A (assuming you use those 3.5A cells). This way your arrangement of 100 LED's will last hours instead of minutes ;)
     
  13. TheButtonThief

    Active Member

    Feb 26, 2011
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    Maybe 2.5mm² but I don't know the length of his cable run ;)
     
  14. Atef94

    Thread Starter New Member

    Aug 23, 2015
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    Im gonna wire them directly no wire used ;) a led is solded into the next one .. Also we do not have good AA here they are super expansive but we have those cheap made in china ones would that still work?
     
  15. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    You know, someone asks how to power LEDs almost every day here, it is the single most common topic. If you need to know the correct way to drive LEDs, search the many existing threads or, just google the subject.

    There is little point in going through the basics of driving LEDs again when it has been covered multiple times.
     
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  16. Atef94

    Thread Starter New Member

    Aug 23, 2015
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    I googled n searched but no one did it this way :/ the question is simple here x) if I use 9volt x2 would I need resistors? Do i need resistors at all ? Im so stuck here :/
     
  17. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Ok, if you read about powering LEDs that blocco suggested, you should have realized by now that you're going to need resistors. Which value depends on the specifications for the LEDs, that you don't seem to have.
     
  18. DickCappels

    Moderator

    Aug 21, 2008
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    What color is the light that you LEDs make?
    This information will help us guess at the required voltage.
     
  19. Atef94

    Thread Starter New Member

    Aug 23, 2015
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    50 are green .. 20 orange and 30 blue ones
     
  20. TheButtonThief

    Active Member

    Feb 26, 2011
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    Always limit current to an LED. Lets assume your LED's have a Vf of 3.3V and a current consumption of 20mA

    Vr=Vcc-Vled

    Vr=9-3.3

    R=Vr/Iled

    R=5.7/.02

    R=285 (round up to closest real resistor value: 300R)

    ...so a 300ohm resistor in series with each LED.

    No wires? LED leads can only handle so much current, use wires.
     
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