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Automotive relay with time delay

Discussion in 'General Electronics Discussion' started by awdowns, Apr 7, 2010.

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  1. awdowns

    awdowns

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    0
    Apr 7, 2010
    I have a project that I would like to do with my car, but I am not exactly sure how to go about it. There is a device called a turbo timer that allows your car to keep running for a set period of time without the key in the ignition. Im trying to make one out of my rear defroster switch and would like to add in a 2nd timed relay for a shorter delay.

    I plan on disconnecting the rear defroster completely and running the power out from the defroster relay to my ignition on relay to keep the car running for about 10 min. But the part I am trying to figure out is putting a 2nd time delay relay with a shorter time (2-3 min) and be able to switch between them with a toggle switch. I basically know how to run everything, but I need help with figuring out what relay I need relay and the toggle switch connection.

    So basically how I want the set up to work is; with the car on and running, select the toggle switch to either turn on the long delay, or the short delay. Then push the defroster switch to engage power to the selected relay, that will allow me to remove my key and keep the car running for either 2 or 10 min and shut off when the power is cut off by the timer.


    Help with this will be greatly appreciated!

    -Steve
     
    Last edited: Apr 7, 2010
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,384
    2,771
    Jan 21, 2010
    OK, presumably you have considered that you frequently drive your car for prolonged periods under high boost and then need to leave your vehicle immediately.

    Presumably you have already looked at the price of real turbo timers and the price of a new turbo and decided that it's not worth getting the appropriate piece of equipment.

    You need to check the rating of the relay used in the demister timer and decide if that is appropriate for switching the ignition.

    If so, you can probably connect the relay wherever the relay in a real turbo timer is connected.

    You should consider how you can kill the engine in an emergency. You don't want to be left in a situation where there is no means of turning off the engine.
     
  3. awdowns

    awdowns

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    Apr 7, 2010

    I have used turbo timers in the past, they do the job perfectly. The reason I want to use the defroster switch is to leave the car as stock appearing as possible. I have no problem purchasing a turbo timer, I just want the challenge of trying something new.

    The way I have in mind would be to put the power out on the defroster relay to the power in to the ignition on relay. That way the rating of the defroster relay wouldnt matter, it would just be switching on the ignition relay. If it works out the way I am thinking, the ignition relay would work like the key is in the on position. Not sure if it helps or not, but the fuse for the rear defroster is a 40 amp fuse, so I am guessing that the relay has to be somewhat similar. 40 amp should be more than enough to run anything in the car.

    I have taken care of any problems that may come out of it by installing an external battery cut off switch, which is also required to pass inspection at some tracks in my area.

    What I need help with most, is finding the correct relay and toggle switch for and to activate the secondary time setting.
     
  4. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    Why do you want to hide the turbo timer? Are you trying to skirt regulations by keeping the inspectors from finding it?

    For aircraft, the problem is solved by having the pilot sit in the seat and run the engine at idle for 3 minutes after touchdown before turning the engine off. If this is a racing vehicle, that will not be such an imposition.

    I find the whole idea of having the vehicle running unattended rather disturbing. It is great for normal operations but EXTREMELY dangerous in an emergency like a fire or a crash. This goes for the system you design as well as any commercial systems that achieve the same thing.

    ---55p
     
  5. awdowns

    awdowns

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    Apr 7, 2010
    Like I said, I want the car to look as stock appearing as possible. Instead of having to mount another box in plain view, which is bright at night, I can use a factory switch in the dash. There are no regulations about a turbo timer. What is wrong with letting your car idle by itself? That is the sole purpose of a turbo time. Haven't you heard of remote start systems? The system will only work if the button is pushed not all the time like a real turbo timer would, also I have an external battery cut off switch to kill the car instantly.

    Instead of telling me its dangerous and asking why I want to do it, can someone please offer me some advice.
     
  6. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    If someone thinks that what you are doing is not safe or otherwise not a good idea, they will not offer you advise on how to do it, even if they can. This is true whether you are doing this or wanting to make a cell phone jammer or a coil gun (those are other people, not you).

    To answer your other question: I feel it is unsafe to have the engine running unattended, whether it is due to a turbo timer or due to an auto-start. When your engine is running, so is your fuel pump. With no one at the seat, the engine will keep running in the event of an engine fire and keep dumping fuel into it. What happens if the timer does not turn off the engine. Will it run all night? If it is in an enclosed space, where will the exhaust go? Depending upon how the system is implemented, there may be a risk of vehicle theft or joyride. It is true that all of these issues can be addressed, but the system is not inherently safe.

    Auto-start has significantly more risks than a turbo timer. Just because a lot of companies make and sell them and a lot of people install them does not make them safe. It only says that they either have a higher tolerance for risk or that they have a lower ability to think through the consequences of their actions.

    ---55p
     
  7. awdowns

    awdowns

    5
    0
    Apr 7, 2010

    Im not really asking how do to it, I already know how I want to wire it. I just need help finding a 12v timed relay.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,384
    2,771
    Jan 21, 2010
    Were you not planning to use your rear demister timer?
     
  9. awdowns

    awdowns

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    0
    Apr 7, 2010
    That is for the long setting, I need a 2nd relay for the short setting.
     
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