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Driving a 12V COB LED ring with a portable battery (beginner's headache)

Discussion in 'Power Electronics' started by Griffevent, Apr 5, 2015.

  1. Griffevent


    Apr 5, 2015
    Hello everyone,
    I'm a French student in literature, so get ready to see plenty of mistakes in the following post (either concerning electronic or basic English).
    I need your help concerning a little project I'm trying to make, but I keep getting slowed down by my misunderstandings of electronics. I read the thread "Got a question about driving LEDs?" but I can't find the answers here either.

    I'm trying to build a portable led ring mounted on an aluminium lens hood to do some macrophotography.

    I've got a COB led ring bought for cheap on a chinese website. The specs' indicate 12W / 12W (so it should draw 1Ah ?), and no resistors are included. Hooked to a car battery (for testing), the light is too strong. It's perfect when hooked to a 10.8V Li-ion hand-drill battery (and it's light and easy to carry).
    Thus, I am looking for an efficient way to drive it.

    > Is it hasardous to hook the 10.8V battery to it without any regulator in the circuit ?
    > Does a more efficient way to power it exist ? It's basically 3x 18650 isn't it ?
    > I can't measure the amps when hooked to the car battery, but a colleague of mine says 12W looks suspicious.

    Thanks in advance for your help.
  2. Colin Mitchell

    Colin Mitchell

    Aug 31, 2014
    If the LED strip has built-in resistors,simply put a string of 4 x 1N4004 diodes on the positive wire.
  3. Griffevent


    Apr 5, 2015
    The specs are lacking in the item description. But according to a website about some extremely similar rings : "There are no resistors on the ring itself, rather, the power is supplied at a constant current through an external regulator, which is then plugged into a 12V source." So I suppose it doesn't have built-in-resistors.

    Here is a picture of the led ring : [​IMG]
    Last edited: Apr 5, 2015
  4. davenn

    davenn Moderator

    Sep 5, 2009

    pic isn't showing
  5. Griffevent


    Apr 5, 2015
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