12V lighting circuit backfeeding problem

Discussion in 'General Electronics Chat' started by carkhz316, Nov 18, 2015.

  1. carkhz316

    Thread Starter New Member

    Nov 18, 2015
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    0
    Hello all, amateur electrical hobbyist here. Self taught with a few books from Radio Shack, and slowly learning. I must admit, I'm a little intimidated posting here as I've never been part of any electronics forum before. Anyway, to cut to the chase, I built this automotive parklight dimmer circuit to be used with switchback LEDs. I've done two of them before, and they worked just fine. The only difference with this one is I added a circuit that would cancel DRL's while the turn signal is engaged. That circuit behaves just fine. The problem is I'm getting a backfeeding problem on the turn signal circuit whenever it's opposite is on. BUT, only when the parklights are turned on. Say the left turn signal is on, the right side will flash a little bit brighter, but not full brightness, and vice-versa when the right turn signal is on. Attached is my quick sketch of the wiring diagram. The dimmer module sends out a PWM 12V to the parklights, and the turn signal voltage sends out a constant 12V that makes the respective LED turn on to full brightness. Any and all help is appreciated. Thanks for your time!
     
  2. wayneh

    Expert

    Sep 9, 2010
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    Just a guess - The load of the lights is enough to pull down the output of your parking light PWM signal. When you put full power to one bank of lights, this reduces the total load on the PWM signal and thus the opposite bank gets a bit brighter. You should be able to test this by temporarily disconnecting the left or right bank of lights receiving power from your parking light dimmer. The opposite side should get a little brighter.
     
  3. carkhz316

    Thread Starter New Member

    Nov 18, 2015
    2
    0
    That makes perfect sense. I just couldn't figure out how it would backfeed at all with the diodes in place. I tested them thinking that maybe one of them was defective, but none are. I will try your suggestion check it out and report back. Probably won't get to the vehicle until the weekend, unfortunately.
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,123
    3,047
    The good news is, it should be a fixable problem. If that's what it is. ;)
     
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