LED light panel problem.

Discussion in 'The Projects Forum' started by RobWheatley, May 19, 2011.

  1. RobWheatley

    Thread Starter New Member

    Apr 19, 2011
    Hello everyone.
    Noob here but need some help.

    I have converted 2 disco light panels from the old style bulbs (christmas tree type running direct from mains) to LED's, there are 4 seperate circuits (blue, red, green and yellow) each containing 48 LED's wired in parrallel. I used 4 LED driver transformers (12v) one for each colour, each LED has its own limiting resistor.
    It is supposed to light each colour in turn (a chase) via a lighting controller, now if I have the chase spped fast it works fine but if I slow the speed down I get the normal flash but I also get ghost flashes at a much reduced power.
    I have tried the unit without the controller direct from the mains to each transformer and when I unplug it I get the ghost flash.
    Im guessing its the transformers that are causing it when they are turned off they are allowing a small pulse through as the power is lost.

    Can anyone suggest a way of either surpressing this or a different type of transformer to use (AC to DC)
    Im not a spring chicken (45) and I teach so no safety issues with building my own unit/s

    I did think of using one transformer and switching the output with relays but didn't really want the relays clicking.

    Thanks for any help.
  2. KJ6EAD

    Senior Member

    Apr 30, 2011
    Do you have a schematic?
  3. RobWheatley

    Thread Starter New Member

    Apr 19, 2011
    No I don't at the moment, I can try and draw one.
  4. russpatterson


    Feb 1, 2010
    What do the connections to the lighting controller look like? Maybe you can put the "switched" part of the circuit between the transformers and the LED banks, thus eliminating the transformer bleed off as there will be no conductivity between the transformer and the LED bank.

    Did you buy or make the lighting controller?
  5. #12


    Nov 30, 2010
    Any inductor (like the winding of a transformer) will try to keep the current flowing for a few milliseconds if it is interrupted (switched off) in mid-cycle of the power line. This might be fixed with a few inexpensive capacitors, but there is no chance of guessing what and where without a schematic.
  6. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    You could use solid state relays and isolate the LED's from the transformer outputs that way. Your controller would have to be capable of providing an 'enable' signal to the relays, or provide a timed signal which could be used to create such a signal.
  7. RobWheatley

    Thread Starter New Member

    Apr 19, 2011
    The controller is a standard 4 channel light chaser unit, it outputs 240V~, I can do a schematic but the transformers are standard LED lighting units so I would have no idea of the circuits in them, it would be very basic too.
    I like the idea of the solid state relays but they would have to be triggered from 240V~
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
    I'm no spring chicken either[ 84 ], so I confuse easily. You only have 192 LED's alltogether? Or multiple banks of 192 LED's. Are " transformers" really just step down transformers, 240:12V AC, or DC power supplies? Why are LED's connected in parallel, rather than series- parallel? Might want to check out Bill's Blog. for 555s & LED chasers. I would be tempted to operate with a DC supply of around 36 to 48V, & 12V for logic; and make my own controller with MOSFET's for drivers.