Hello new here ....

Discussion in 'General Electronics Chat' started by mariuszjj, Apr 25, 2013.

  1. mariuszjj

    Thread Starter New Member

    Apr 25, 2013
    Hello new here ....
    and gonna start by asking few questions
    what would i need to make Led circuit with reversing
    polarity? ( the power is Ac ) used for model trains
    ( most the i use for normal lighting is square bridge / cap and
    led strip - includes resistors on it already .... )
    if i wanted to make red and white leds to switch based on polarity how would i do that?
  2. #12


    Nov 30, 2010
    Welcome, but we need a more definite description. Please ramble on.
  3. Brownout

    Well-Known Member

    Jan 10, 2012
    Typically if you are using an LED with A/C, you connect a rectifier diode across the LED (anti-parallel) so that reverse polarity current goes around the LED. But there is more to it. You need to current limit the foward current to a safe level.
  4. Mike33

    AAC Fanatic!

    Feb 4, 2005
    If it runs on AC, how will you determine when it is going forward or backward? Most of the more advanced engines have a circuit board in them that 'knows' what's going on - that's where the action is.

    If you always have AC at the track, it won't be changing with motor direction - or am I missing something? *Shrug*

    You CAN (and probably should) use DC for your lighting, however, and change polarity for lights - I did this for my father in law's train with good results.