advice on a timing circuit for headlamps

Discussion in 'The Projects Forum' started by mshale, Oct 12, 2007.

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  1. mshale

    Thread Starter New Member

    Sep 25, 2007
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    Hi all!

    This is my first post! I'm a student in Electrical engineering, but i'm not quite through my second year yet so i've not had the major circuits course.

    I don't think I can wait any more on this project, for I am a forgetful man... lol

    I have a Nissan Xterra (2000) and it doesn't have that neat feature of auto shutoff lights that a lot of vehicles have nowadays. So, I plan to add that feature :) See, I have come back to a dead battery many times because I leave the lights on.

    I have this all planned... i'm going to move the main power of the headlamps to come from the ignition switch instead of directly from the battery and put the circuit in between the ignition and the factory headlamp switch. That way, I still have a little control over the lights.

    Do any of you have any suggestions on how i could improve the circuit? And is that 12V relay just one of those that I can buy at an auto parts store i.e. an 85, 87, etc. relay?

    The circuit is attached! (actually, It probably needs to look more like LightsCircuits2 doesn't it, or are 1 & 2 the same?)

    This circuit is supposed to delay the power-on for 7 seconds (lessen battery load while starting the engine) and delay-off to allow me to see where i'm walking at night for 15 seconds. I have all of the resistor/capacitor values set.
     
  2. mshale

    Thread Starter New Member

    Sep 25, 2007
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    Basically, what I need to know is this: Is it ok that circuit 1 has all of the grounds connected, and will this circuit do it's job. I have also edited the first post to say what the circuit is supposed to do...

    Thanks for looking!
     
  3. thingmaker3

    Retired Moderator

    May 16, 2005
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    You've got three leads coming off your relay coil. I've never seen a relay coil with three leads...
     
  4. mshale

    Thread Starter New Member

    Sep 25, 2007
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    If I'm not mistaken, it just simply omits the ground lead as understood.
    I just got these off of Bill Bowden's site (did a google search for "delay off bowden") if you are interested in lookin at it further.
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
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    I'm not referencing an omission, I'm referencing an extraneous lead. The coil should only have two leads.

    You've connected the input to the delay off circuit to the coil of the delay on circuit.

    Was your intention to drive the off delay from the relay contacts of the on delay? Like this: LightsCircuit2.jpg
     
  6. mshale

    Thread Starter New Member

    Sep 25, 2007
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    That is precicely it. So that the load on the battery is lessened while starting the vehicle.

    The reason I say it's missing a ground is that the standard automotive relays have 4 terminals. one for a 12V power, one that gets power to turn on (eg. a switch), a ground and an output. maybe this drawing is just missing one of those termnals?

    What do you think?
     
  7. thingmaker3

    Retired Moderator

    May 16, 2005
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    I think it will work. I think I might try one in my old Ford Ranger.
     
  8. mshale

    Thread Starter New Member

    Sep 25, 2007
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    Great! If you do try it, lemme know how it goes. I'm in the process of finding the wiring diagrams for my Xterra, getting the components, and finding the time lol. I have a major electrical project in store for it :)
     
    Last edited by a moderator: Sep 16, 2012
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