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11049 Views 2 Replies Latest reply: Apr 23, 2012 5:55 AM by M.Emara RSS
Currently Being Moderated

Mar 28, 2012 4:20 PM

how many watts to a battery

Hello all!!

I want to make battery operated christmas lights but im not too sure how many batteries to use?

do i have to do some calculations to figure this out. Thanks for looking

  • richcj10 Novice 8 posts since
    Mar 26, 2012
    Currently Being Moderated
    Mar 29, 2012 7:07 PM (in response to micheya)
    how many watts to a battery

    no point in starting a new thread.... look at my question on the first thread you started...

  • M.Emara Novice 37 posts since
    Sep 14, 2011
    Currently Being Moderated
    Apr 23, 2012 5:55 AM (in response to micheya)
    how many watts to a battery

    Show more deatils please!! what is the power of lights you want to operate? Sure you must do calculations to know, how much energy you need to operate your lighting system, maximum volt and current. These lights are blinking or just stable lights?

     

    First of all this website is pretty helpful, take a look on electronics components:

    http://www.kpsec.freeuk.com/

     

    I will try to make the idea clearer for you. Let’s make a stable lighting system consisting of 1 LED (5mm).

     

    Basic information about LEDs (Light Emitting Diodes), check this link please:

    http://www.kpsec.freeuk.com/components/led.htm

     

     

    Components:

    (5mm) Red LED -----> #1

    Signal Diode (normal Diode) -----> #1

    Resistor

    Switch on- off

    9V Battery

     

    Before deciding the size of the needed battery for operating your system, you must know the forward current (IF) and forward voltage (VF) of the used LEDs in system. If you can’t take LED specs from supplier, you can use this table as a guide. The table below shows typical technical data for some 5mm diameter round LEDs.

     

    Type

    Color

    IF
    max.

    VF
    typ.

    VF
    max.

    VR
    max.

    Luminous
    intensity

    Viewing
    angle

    Wavelength

    Standard

    Red

    30mA

    1.7V

    2.1V

    5V

    5mcd @ 10mA

    60°

    660nm

    Standard

    Bright red

    30mA

    2.0V

    2.5V

    5V

    80mcd @ 10mA

    60°

    625nm

    Standard

    Yellow

    30mA

    2.1V

    2.5V

    5V

    32mcd @ 10mA

    60°

    590nm

    Standard

    Green

    25mA

    2.2V

    2.5V

    5V

    32mcd @ 10mA

    60°

    565nm

    High intensity

    Blue

    30mA

    4.5V

    5.5V

    5V

    60mcd @ 20mA

    50°

    430nm

    Super bright

    Red

    30mA

    1.85V

    2.5V

    5V

    500mcd @ 20mA

    60°

    660nm

    Low current

    Red

    30mA

    1.7V

    2.0V

    5V

    5mcd @ 2mA

    60°

    625nm

     

    Red LED (5mm): VF = 2.1(V), IF = 30mA.

     

    Connect battery in series with, on-off switch, signal diode, resistor, LED. Let’s say that we are using 9V battery. Don’t forget that forward voltage of signal diode is 0.7V so volt after diode will be V(battery) – V (diode), 9 -0.7= 8.3V

     

    Value of Resistance = ((V(battery) – V (diode) – VF) / IF) = ((8.3 – 2.1/ 30 X10-3) = 206.67 OHM, to use a standard value of resistance 220OHM (1/2W)

     

    The link below show how to calculate value of limtting resistor:

    http://led.linear1.org/1led.wiz

     

     

    Kind Regards

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