Simple 12v Relay information

Discussion in 'General Electronics Chat' started by Twain427, Feb 16, 2013.

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  1. Twain427

    Thread Starter New Member

    Feb 16, 2013
    I am well aware of 12v relays and their function. What I am looking for is similar in function, but offers the opposite. Where areas a typical 12v relay switches power on and off when triggered, I am looking for a relay that stops the flow of power when triggered. In other words, when not triggered by a power source it allows for the flow of current but stopped when triggered.

    I believe there to be a relay/device available that will accomplish such a task, however not knowing the exact name has made googling such very difficult.

    To help, I am attempting to add daytime running lights to my vehicle. I would prefer for the lights to run at all times when the vehicle is running except when the headlights are on. Hence the relay I describe... When the headlights come on they trigger this relay to cut power to the daytime running lights.

    Thanks in advance for any assistance.
  2. tracecom

    AAC Fanatic!

    Apr 16, 2010
    A double throw relay (also called a C form relay) does exactly what you want. It has two sets of contacts: a normally closed (NC) set that are closed when the relay coil is not energized and a normally open (NO) set of contacts that are open when the relay coil is not energized. Whatever is attached to the NC set of contacts will be connected when the relay coil is not powered.
  3. Georacer


    Nov 25, 2009
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