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Relay circuit for LED daytime running lights?

Discussion in 'LEDs and Optoelectronics' started by Nate Miller, Feb 2, 2016.

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  1. Nate Miller

    Nate Miller

    3
    0
    Feb 2, 2016
    Hi,
    I'm working on a project for my car that I was hoping to get some help with. I am putting some LED's behind my custom grill emblem on my 2007 4Runner to backlight it. I have some white LED's that are connected to my Daytime Running Light circuit so that when those are on the white LED is on, but I have a red slow pulsing LED that I want to put behind there with some kind of relay that will turn it on when the Running Lights are off. So I'm wondering if anyone can help point me to a 12V relay that would do just that.

    Thanks!
    Semper Fi,
    Nate Miller
    (Sgt, USMC Retired)
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,811
    2,751
    Nov 17, 2011
    You can use any relay with a 12 V DC coil (e.g. automotive relay) with a normally closed contact (closed when not energized).
    Put the relay coil in parallel to the daytime running lights. This willl activate the relay when th edaytime lights are on, thus opening the normally closed contact.
    Use this contact to route power (12 V) to the LED blink circuit.
    Thus, when the daytime lights are off, the relay is de-energized, the contact closes and the LED starts to blink.

    Regards,
    Harald
     
    Nate Miller likes this.
  3. Nate Miller

    Nate Miller

    3
    0
    Feb 2, 2016
    Do you happen to have a link to the kind of relay I'd need? I'm finding all sorts of different relays with 12 pins, 8 pins, 4 pins, etc etc. And I'm not sure what to look for to find a "normally closed" relay and how many pins I need or how to wire it up.
    Sorry for all the questions but thanks for your help!

    Semper Fi,
    Nate Miller (Sgt USMC Retired)
     
  4. cjdelphi

    cjdelphi

    1,096
    104
    Oct 26, 2011
    The cheapest relay you can find will do the job...

    Usually they come in 5 pins (energize the coil 2 pins) the other 3 are the switch, depending how you want it to behave...
     
  5. cjdelphi

    cjdelphi

    1,096
    104
    Oct 26, 2011
    Just make sure it's 12v rated..
     
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