Garden lights

Discussion in 'General Electronics Chat' started by garybuska, Aug 13, 2014.

  1. garybuska

    Thread Starter New Member

    Aug 12, 2014
    Hello all
    I am new here and have a question.
    I have one of those round globes that are solar powered and has a single LED in it.
    My question is how does the single two lead LED manage to turn different colors.
    I have heard elsewhere that this is due to TWO LED'S combined into one package.
    I have looked very closely and for the life of me I can not see two separate ANODES and CATHODES in this unit.
    So how is this done?
    I have noticed that the one common thing I have found in these items is the fact that they all use two AA rechargeable batteries.
    I even discovered that if you take the LED out and connect it to a 3 volt battery it will change colors
  2. bertus


    Apr 5, 2008
    MrSmoofy likes this.
  3. garybuska

    Thread Starter New Member

    Aug 12, 2014
    Thanks for the reply
    I could not figure out how this was being done
  4. anhnha

    Active Member

    Apr 19, 2012
    According to the specifications, Total Power Consumption is 0.252 Watts.
    How do you calculate that number?
    The forward voltage is 3.8 - 4.2V but the current varies in a wide range. So, how do you figure out that fixed power consumption?:confused:
  5. wayneh


    Sep 9, 2010
    Here we go again with rms power calculations!

    Technically, you have to integrate instantaneous power over time to get the average power. There are various shortcuts, including using average voltage times average current. That's not correct, but is close enough for a garden light.
    anhnha likes this.
  6. MagicMatt


    Sep 30, 2013
    They'll have to be using an average anyway, since the power consumption of those colour changing LEDs varies slightly depending on what colour it is outputting at the time. Doesn't really notice on one... notices more when you're driving 250 of them on a string...
    anhnha likes this.
  7. anhnha

    Active Member

    Apr 19, 2012
    As you said, the average power consumption is calculated from instantaneous one.

    Pavg = average {Pinst}
    Pinst = i^2*R
    Where R is the internal resistance of the LED. Yes?
    Now for example, the power supply is an ideal battery 5V.
    How do you calculate intansaneous power consumption?
    I think an external resistor is needed to limit the current.
    The specifications doesn't list current range, so how to know that range and from there calculate power consumption?
  8. adamclark


    Oct 4, 2013
    Ive got some of those solar garden butterflies that changer color. I figured it was just an RGB LED that had an ic changing voltages to make it cycle through al the different colors.. Im not trying to hijack your thread, but thanks for the math to figure rms power..