In today’s modern car we all look to buy the latest and greatest technology available to us at our disposal. Keyless entry in cars have been around for a while. Most of us owning a car with keyless entry would have had a thought about what will happen to the car when the start/stop button is pressed accidentally while driving. Lets find it out.
What
is keyless entry in cars?
The fob that you carry on your keychain is actually
a small radio transmitter. When you push a button on the fob, you turn on the
transmitter and it sends a code to the receiver. Inside the car is a radio
receiver tuned to the frequency that the transmitter is using (300 or 400 MHz
is typical for modern systems).
With the remote keyless-entry systems that you find
on cars today, security is a big issue. If people could easily open other
people's cars in a crowded parking lot at the mall, it would be a real problem.
And with the proliferation of radio scanners, you also need to prevent people
from "capturing" the code that your transmitter sends. Once they have
your code, they can simply re-transmit it to open your car.
Below photo below shows you the guts of a typical
key-ring controller for a modern car
You can see that everything has been miniaturized.
There is a small chip that creates the code that gets transmitted, and the
small silver can (about the size of a split pea) is the transmitter.
The controller chip in any modern controller uses
something called a hopping code or a rolling code to provide security. It is a
system that uses a 40-bit rolling code. Forty bits provide 240 (about 1
trillion) possible codes. Given a 40-bit code, four transmitters and up to 256
levels of look-ahead in the pseudo-random number generator to avoid De-synchronization,
there is a one-in-a-billion chance of your transmitter opening another car's
doors. When you take into account the fact that all car manufacturers use
different systems and that the newest systems use many more bits, you can see
that it is nearly impossible for any given key fob to open any other car door. You
can also see that code capturing will not work with a rolling code transmitter
like this.
My answer applies to much of the latest cars where
everything is computerized and integrated to infotainment system as well.
A push Start/Stop button is similar to the power
button on your cell phone. Your cell phones shuts off or reboots only when you
long press it. Else, it doesn't do anything for short press when the phone is
off and it toggles screen on and off when the phone is on. Because, the Cell
Phone microprocessor chip is programmed that way. Similarly, modern cars also
have a micro processor which is programmed to respond to all the buttons in
your car. There could be many such processors - one for ingnition, one for
engine, one entertainment system and so on.
So, a car's ignition to be turned ON or OFF is
programmed only when it is in
1. Park gear (button 1)
2. Break pedal is pressed (button 2)
3. Push Start is pressed (button 3)
4. Check 0 speed (may be)
So, the processor could be programmed to start the
car like,
If the car speed is zero and if button 1 and 2 and 3
are pressed, only then send signal (spark) to the ignition to turn it on. If
you accidentally press the start/stop button, your engine won’t stop at least
in the latest cars. However you can stop your car even when it is cruising by
holding the start/stop button for 3 seconds. You can watch the video on the
same with link below.
https://youtu.be/i-GsIPBEnp8
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