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130 LED's on 1 resistor

Discussion in 'LEDs and Optoelectronics' started by greenhill85, Jan 14, 2011.

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  1. greenhill85

    greenhill85

    4
    0
    Jan 14, 2011
    hi I need to wire 130 leds to a 5volt supply is there a way to do this with out using 130 resistors


    LED'S used

    3mm
    10000 mcd (ultra bright)
    Forward Voltage : 3.2v – 3.8v
    Forward Current : 20mA (Typical) 30mA (Max)

    supply

    5 volt usb

    I would like to know an easy cheap but effective way to drop the voltage to 3.3 so that I can run the led's but not burn them out. prefer not to use 130 resistors as there is not a lot of room

    thanks for any help you can give

    (complete noob)
     
  2. Mitchekj

    Mitchekj

    288
    0
    Jan 24, 2010
    Sounds like you'd have to run them all in parallel, in that case your USB must supply upwards of 2.6A.

    As far as I know, 500mA is the max USB output? Maybe 1A?
     
  3. Ian

    Ian Administrator

    1,487
    436
    Aug 23, 2006
    Yep, generally speaking USB 2.0 (most common) is 500mA and USB 3.0 is 900mA :)
     
  4. greenhill85

    greenhill85

    4
    0
    Jan 14, 2011
    thanks for the replys you are right the usb is 500ma looks like a rethink is required will probably go for a external plug supply or try to lower the amount of leds and run them on the usb
     
  5. greenhill85

    greenhill85

    4
    0
    Jan 14, 2011
    hi guys just had a look on ebay and found this external plug supply can i use this or will i have a problem with it being 5 volt

    5*Volt*2.6 Amp*DC Regulated Power Supply
    Top quality power supply suitable for driving various items of electronic equipment.
    This is an AC to DC power supply - it transforms 100-240v AC to 5v DC. It has a regulated 5v DC output and can supply from 0.01a (1ma) to 2.6a (2600ma) making it ideal for any piece of equipment that requires 5v DC at up to 2.6a.
    Features:
    100v to 240v AC Input
    Plugs directly into UK mains socket
    5*Volt DC,*2.6a regulated output

    once again thanks for all your help
     
  6. greenhill85

    greenhill85

    4
    0
    Jan 14, 2011
    hi guys if i use the power supply above at 2.6 amps which is needed will i still need a resistor if they are wired in parallel or will they automaticaly share the 2.6 amps between them
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,500
    2,840
    Jan 21, 2010
    Read the sticky about driving LEDs.

    You should really have 1 resistor per string of LEDs. To minimise the number of resistors, use a higher voltage power supply (say 12, 24, or even 48 volts).

    They will not share current. In fact, one will tend to hog the current and blow. Then another will hog the current and blow, then another... (you get the idea)
     
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