dimming LED lights

Discussion in 'The Projects Forum' started by sky jumper, Jun 14, 2013.

  1. sky jumper

    Thread Starter New Member

    Jun 14, 2013
    2
    0
    newbie here.

    I bought some new outside LED lighting fixtures for the garage and front door. they are too bright and annoy the neighbors. they consist of 3 LEDs in series running off a 10V 700ma supply.

    to dim them I put a 2.2k resistor in series. now they flicker.

    I then put a 33uF cap in parallel. flicker is reduced, but still flickers.

    I also tried to disconnect 1 or 2 of them. the remaining ones flickered.

    is there a quick way to dim these without having to build a fancy PWM controller??

    and, could someone explain to me why they flicker? I'm an EE but have long forgotten the basics of LED circuit design.
     
  2. antonv

    Member

    Nov 27, 2012
    149
    27
    Is the supply a constant current 700mA supply specifically for driving LEDs?
     
  3. #12

    Expert

    Nov 30, 2010
    16,316
    6,818
    How about a piece of colored plastic for a lens? It's not an electrical idea at all, but if you're resourceful and lucky, you might get a good result.
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
    Open the psu up and alter the current setting to suit.
     
  5. sky jumper

    Thread Starter New Member

    Jun 14, 2013
    2
    0
    I'm not sure about the specifics of the power supply. it says 6-10V DC output, 700ma. it's part of the fixture, so I'd assume it was designed specifically for this application.

    I may try the colored lens idea -- i thought of that but couldn't readily find a suitable plastic lens that would fit. I have tons of resistors...

    I could try to open the power supply. it appears to be a sealed unit. but if I could open it, how would I know how to alter the design parameters without schematics?
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,061
    3,823
    Get a piece of white polycarbonate from the home improvement store. If they don't have white, get clear and wipe acetone (fingernail polish remover) on it until it is fairly opaque. Make sure you remove the protective film from the poly sheet befor treating with acetone (it will be obvious if protective film is present).

    You can also go to the thrift store and buy a glass dome from an old light fixture and break it to a size that fits over your LEDs.

    To stop the flicker, you may need a much larger capacitor (3300 to 6800 uF) if you go that route. You may not have space for that.
     
  7. #12

    Expert

    Nov 30, 2010
    16,316
    6,818
    Now it is the next day and I thought about the "blinkers" that go on horses. Flat plates that narrow the beam so it doesn't shine on the neighbors. Another idea is to cut slots in a piece of sheet metal to direct the light and misdirect some of it so it doesn't get out of the fixture.
     
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