Timed trigger relay help?

Discussion in 'The Projects Forum' started by WuNgUn, Nov 20, 2006.

  1. WuNgUn

    Thread Starter New Member

    Nov 20, 2006
    9
    0
    I've built a simple push-button starter for my car, based off a DEI remote car starter. Basically, it operates the program when the remote starter sees two pulses from the button. This is the easy part...
    But when I want to run accessories WITHOUT starting the car, I want to build a type of timing device/relay that ONLY activates the accessory circuit latch relay when it sees a steady, 2 second trigger from the same 'start' button.
    And on the same note, I need the same timer to turn OFF the accessory circuit thru the (latching)relay when it sees another 2 second trigger hold...
    Thankfully, the remote starter ignores this signal, and only operates on two quick pulses.
    But this timing device HAS to ignore any other pulse triggers from the same button...I need it to only operate when it is held for 2 seconds.
    The latching relay hooked up to this uses two positive inputs...one to close the circuit, the other to open it, which no doubt, complicates matters.
    Can someone please help?
    Thanks
     
  2. WuNgUn

    Thread Starter New Member

    Nov 20, 2006
    9
    0
    Maybe a 555 based countdown timer that is set to 2 seconds, outputed to a latch relay, and only starts counting when power is supplied by the push button?
    But how to reverse the the latch on the next 2 second trigger?
     
  3. EngineerJoe

    Member

    Nov 4, 2006
    15
    0
    You might want to start from the output and work toward the input. Will the latching relays want a pulse or can they tolerate a constant input voltage? Can you do this without disabling the existing inputs? I assume you will need to isolate (with diodes) your input from other inputs! The inverse function problem might be handled using the dual outputs from some type of flip-flop latch. The output from the 2 second verification circuit can toggle the flip-flop and/or clock in the data (which comes from the Qbar [inverted] output).

    A 555 timer will ignore other trigger pulses while it is timing out. That makes it a decent choice because there are so many things that you can do with a 555. You could use a 556 (dual 555) where the second one is used to generate a clock pulse based on the output of the first one.

    It sounds like you may want to research or experiment with some parts before you go to too much trouble. Have fun!
     
  4. WuNgUn

    Thread Starter New Member

    Nov 20, 2006
    9
    0
    This is my crude schematic of a push-button starter for the car...

    There are two buttons...one for start, one for stop.
    Two pulses starts the Viper alarm auto-start into action...holding the button four seconds activates the acc/ign relays without starting.

    The timer is also used to kill the auto-start sequence at the Viper after the car is started (as long as it's started within 4 seconds!)

    Problem is, when I hit the stop button (when the acc/ign relays are powered on), it shorts out somewhere!
    The latch relay latches with the polarity one way to the coil, and unlatches with reverse polarity to the coil. This is what makes me think there is current (or ground) still going to the "latch" when I "unlatch" it, causing the short.
    I can't figure it out :(
    Can you help?
    [​IMG]

    BTW, for bench testing, I hooked up all the + leads and all the - leads together...i.e. power for the buttons, power to the relays...I don't see how that could of been a problem though.

    Here is the latch relay I'm using...

    [​IMG]

    [​IMG]

    There is currently some discussion going on here about this design, which might explain it a little better...

    http://www.mp3car.com/vbulletin/gen...3280-any-electronics-experts.html#post1238430

    I'd love to be able to fix this! Thanks!
     
  5. WuNgUn

    Thread Starter New Member

    Nov 20, 2006
    9
    0
    Bump???
    This is driving me crazy...
    Any obvious problems?
     
    Last edited: Jul 30, 2008
  6. WuNgUn

    Thread Starter New Member

    Nov 20, 2006
    9
    0
    Double-bump?
     
  7. AllVol

    AAC Fanatic!

    Nov 22, 2005
    55
    2
    Is the circuit shown on the Mpcar page what you are doing now?

    If so, the timer portion should not work since you are connecting the bottom half of the switch to pins 1 and 4 of the latch(?) through a capacitor. Since capacitors block current at dc, whatever that circuit is supposed to do isn't happening.
     
  8. WuNgUn

    Thread Starter New Member

    Nov 20, 2006
    9
    0
    I don't have the capacitor installed actually...I wanted to use it to "delay" the current going to the timer, so it wouldn't see power when I was double pushing the start button.
    But this doesn't have any negative effects on the timer, so I left it out..
     
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