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Safety issue for keyless Start

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windozeuser

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I'm making a blue-tooth keyed push button start for my car, it uses your phone as the key, uses simple encryption with the signal. Wont allow you to start the car without the phone present,

My main concern is that I dont want my car to have any possibility to ground out and shutoff while in motion. If there is a malfunction with the Arduino or something.

Could I use an SCR to "latch" the ignition wires up to 12 volts constant, then it can only unlatch with the signal from the Arduino when you press the button again, but if the Arduino fails it would still not turn the car off while in motion?

I just dont want my car to shut off going down the highway 70MPH haha any ideas to improve the design?

Its an Auto transmission so no worries about the increased safety issues with manuals
 
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Possibly latch it, isolate the control circuit, from a latch circuit, so if in motion, and control circuit fails, the latch will not
 
An SCR would be an ideal solution but they will only stay on if the anode/cathode current is above the holding current when the gate drive is removed, you need to make sure the circuit will draw the proper holding current, if it doesn't you could bypass it with a transistor to keep it loaded.
 
Just make sure you have a bypass. You don't want to be stranded if your phone is lost, stolen or dead.
 
I have a commercial keyless entry on my vehicle. It's been flawless, it however has a key backup inside the fob.
 
You need to have a look at the way commercial units are wired to cars.
As a failsafe the car should still operate normally even with the remote starter disconnected.
 
I'm gonna have a fail safe under the seat using a universal ignition switch so I just reach under and turn the key under the seat to bypass the entire system as normal
 
Generally in an alarm system, the "starter enable" is wired normally open that isn't the same as the "start" push button. I had to add a start PB to a car because my mom could not turn the ignition unless she used pliers. The pliers were not used on the key.
 
Do you guys think if the Arduino is constantly powered from the 12V battery of a car that it would run the battery down? Or there has to be like a low powered stand by mode or only turn it on when the door opens or something. I kinda want to have a keyless entry too so the Arduino will have to be waiting for a signal to open the doors too
 
Some processors will power down to a very low current draw. Some or all interrupts can wake the processor up. Not sure about the Arduino architecture.
 
In addition to the processor current, you also need to look at the quiescent current of the power supply.

For instance, the 7805 draws about 5mA even when it is not loaded. It may be small enough to ignore in many applications, but it is not zero.

There are other regulators that have much lower quiescent currents. The LP2951 is only 75uA. I'm sure there are others out there that are even lower.
 
I see you are posting from the US. There are (in Europe) certain things you cannot mess with on a car as failure could cause a massive problem (failing in the outside lane of a Motorway or Freeway could cause a pile up). Ignition systems are a start. If it is found it's down to your flakey circuit then you could be done for millions.
A nice idea but I would put it to bed.
 
I see you are posting from the US. There are (in Europe) certain things you cannot mess with on a car as failure could cause a massive problem (failing in the outside lane of a Motorway or Freeway could cause a pile up). Ignition systems are a start. If it is found it's down to your flakey circuit then you could be done for millions.
A nice idea but I would put it to bed.
Thats why it has to go in parallel with the Ignition and have all the other safty stuff.
 
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