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How to switch something as soon as power is applied

Discussion in 'General Electronics Discussion' started by AndyT4, Nov 9, 2015.

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  1. AndyT4

    AndyT4

    1
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    Nov 9, 2015
    Hi,

    Please can someone tell me if there is a simple solution to this problem?

    I work in a car dealership (non-technical staff).

    All of our new models have the stop/start technology so that they stop when people are stationary in traffic, at junctions, etc.

    Many of our older customers are confused by this technology and would dearly love to switch it off.

    Unfortunately, due to the requirement to comply with emmissions standards, it is not possible to switch this functionality off permanently. You have to press the button (it is an actual button, not a stalk function) each time you get in the car to disable the stop/start. Press once to switch off, press again to switch on. As soon as you turn the ignition off and back on again, the stop/start function is re-enabled and you have to press the button again.

    I was wondering if there is some simple component/circuit that when connected to the pins at the back of the switch will automatically make the circuit as if the switch had been depressed once to switch it off? Even if you have to apply permanent power to this extra componentry? Forgive me, I am electronicaly thick!

    Thanks for any advice :)
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,702
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    Nov 17, 2011
    You aren't working for VW, are you :D

    A quite simple solution consists of a 12V relay. Coil connected to some power supply voltage (12V) that is present as soon as the ignition is turned on (e.g. dashboard light), contacts connected in parallel to the pushbutton's contacts. But then you (or your customers) will be violating emission standards...
     
    Arouse1973 likes this.
  3. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    And whomever modifies the oem wiring voids their warranty on the vehicle.
     
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  4. Martaine2005

    Martaine2005

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    May 12, 2015
    I was going to say that this afternoon!!!

    Martin
     
  5. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    If they are confused by the technology, they would also be confused about modifying their cars circuitry.

    I would hack my own car, but no way would I ever modify someone else's car.
     
    Harald Kapp likes this.
  6. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    :D
    Afternoon? Should be nighttime on your side of the pond.
     
  7. Martaine2005

    Martaine2005

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    May 12, 2015
    7:30pm.......I do sleep early, but come on John!!!
     
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  8. Tha fios agaibh

    Tha fios agaibh

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    Lol.
    I didn't say you had to go to bed Martin, I just said it was nightime over there.
     
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  9. Martaine2005

    Martaine2005

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    May 12, 2015
    John, It is dark...OK..
    It is not late, OK
    But if you tell me to go to sleep, I will listen..:p

    Martin
     
  10. AnalogKid

    AnalogKid

    2,525
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    Jun 10, 2015
    Assuming this is a low power function such as a switch into a uC that then controls the engine, then:
    1. Small reed relay across the switch with a capacitor in series with the coil.
    2. Optocoupler across the switch with a resistor and capacitor in series with the LED. This is for when the voltage polarity across the switch is known, but you don't want to risk a grounding issues.
    3. FET or BJT switch with RC delay if you are sure about the grounds.

    etc.

    ak
     
  11. BobK

    BobK

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    Jan 5, 2010
    A better solution is to exp!ain the feature and why they want it. In my Prius you don't even notice when the car starts unless you are paying attention to it.

    Hacking the car to reduce its gas milage sounds like a dumb idea to me.

    Bob
     
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  12. Alec_t

    Alec_t

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    Jul 7, 2015
    Apart from invalidating any warranty, would such a wiring mod also invalidate the driver's insurance (it would this side of the pond)?
     
  13. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    No. Not to my knowledge.
    As long one is in control of their vehicle, insurance should not be impacted by it. Of course, I could understand a claim being denied after a fire if there was obvious signs of improper wiring, but most insurance companies would likely not even bother to investigate.
     
  14. Kiwi

    Kiwi

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    Jan 28, 2013
    You could connect the winding of a normally open relay to the start switch and the contacts to the override button. The relay closes every time you start the engine and disables the stop/start system.

    BUT, WHY WOULD YOU WANT TO DISABLE THIS SYSTEM?
    As BobK said, it would be better to explain the purpose and operation of the system, than just disable it "because my old car didn't have this function".
     
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