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Engine start/stop help

Discussion in 'General Electronics Discussion' started by Veltboy618, Mar 28, 2011.

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  1. Veltboy618


    Mar 28, 2011
    Hey guys. I'm new to the site. I haven't been to school for electronics but I have repaired a few things in the past & I'm always wiring stuff up lol. I'm in the process of making a push button start kit for my older car so I don't have to use any keys to start it like the newer cars. I want to car to be a little secure so I'll be using a hidden RFID transponder so without the key fob my car will not start.

    I have a NO momentary "engine start" switch,


    & I have a RFID transponder with 2 key fobs

    When the key fob is brought within 3 inches of the antenna on the RFID brain, the unique date encoded in the key fob is transferred to the sensor-receiver, activating the device-relay & the relay will turn on my ACC, & ignition. I will keep the fob my back pocket & the antenna will be fished up into my seat so when I sit down the brain will be able to read the code of the fob.

    The engine start button will be wired to receive power once I press the brake pedal. When I press the "engine start" switch & close the circuit it will send power through a relay (getting power directly from the battery) then to the starter to engage it.

    Once I press the button to engage the starter the car will start but here is where I confused. When I press the button to start the car I need the starter to stay engaged until I release the button (older cars take a little longer to start sometimes) then I want the same button to shut the engine off when pressed again instead of engaging the starter and making it grind against my flywheel. I was reading in a another thread and someone mentioned a D flip-flop. I looked into it a little & it seem like it can work for what I'm trying to do here. What do you guys think? Could someone help me draw this out so i can be wired up if it's even possible. Any input is appreciated!

  2. Veltboy618


    Mar 28, 2011
    can anyone help me here?
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    OK, same problem as a recent one with starting a motorbike with a similar arrangement:

    1) if the RFID tag falls off your keyring while you're driving, you don't want bad things to happen.

    2) KISS

    I would recommend that the RFID device just be something else in series with the start switch, the brake switch, and the starter solenoid relay. That way you have to have your foot on the brake, your finger on the start button, and the RFID tag near the sensor for the starter to operate,

    The easiest option is to have another switch "Stop" or "Kill" that disconnects power to the ignition (and perhaps fuel pumps etc.)

    The problem with this is that you still have to have a method for applying power to the ignition and other ephemera before you press start. If this is not key operated then someone can still push start your car.
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