I have a button in my Electric car, with a small LED in it. By default when I turn on the car, the LED in the button lights up. Pushing the button turns the LED and the Fake engine noise OFF. The button is controlling a Fake engine sound generated at low speed. But I do not want this functionality and now I manually have to push the button everytime. There is no way to change the default state.

What I would like is that when the LED turns ON, it should simulate that I push the button to turn it off. Preferably with a small delay to prevent multiple button presses. And I also imagine that it could be self powered by the current going to the LED.

So I was wondering if anyone could help me design a small circuit or point me to a ready solution?

I tried to search but most I found includes microcontrollers, and I want the circuit to be as small and simple as possible as I want it to be near the button, and not needing external power.

  • 2
    Can you edit your question to explain why you haven't unplugged the switch? What is this mystery button's intended function?
    – Transistor
    Commented Sep 13, 2017 at 11:29
  • 2
    Without a circuit schema, it's impossible to help you.
    – MatsK
    Commented Sep 13, 2017 at 11:35
  • I'd think that the function that is activated on engine start-up might be important. What function is it? Why do you not want it?
    – Egor Tamarin
    Commented Sep 13, 2017 at 11:46
  • 4
    Is the "fake" engine noise audible outside the vehicle? I have heard that since electric cars are so quiet that pedestrians are at risk from possibly walking in front of unseen (and unheard) electric vehicles. if so, this may be a safety feature that you do not want to bypass.
    – CRJ
    Commented Sep 13, 2017 at 11:58
  • 2
    Disconnect the speaker.
    – R Drast
    Commented Sep 13, 2017 at 12:51

1 Answer 1


It may require some experimentation to get it right, but perhaps a small reed relay will do what you want. Connect the coil in series with the LED, and connect the contacts in parallel with the switch.

  • That is a good idea, I will try to get hold of one. Could I add a few components to get a small delay before it switches?
    – Eldaria
    Commented Sep 13, 2017 at 13:37
  • As @matsk already said, it's impossible to be more specific without seeing the details of the car's wiring (schematic diagram).
    – Dave Tweed
    Commented Sep 13, 2017 at 13:49
  • You could have the small delay using an Arduino. It costs some amount of money, but then again it will be much easier to create a delay using Arduino when compared to designing your own circuit.
    – juhist
    Commented Sep 13, 2017 at 17:10

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