Re: Fail-safe for keyless entry

["Robert Green" <robert_green1963@xxxxxxxxx>]

<mkirsch1@xxxxxxxxxxxxxxxx> wrote in message
news:84d0ed23-119c-4351-a40e-f9563135a490@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Apr 19, 12:50 pm, "Robert Green" <robert_green1...@xxxxxxxxx>
wrote:
> The real estate inside the fob is very cramped. It runs off a CR2032 coin
> cell battery, and the circuit traces are simple enough so that I could
> scrape off the 3VDC+ line and bridge it with a small switch. That way, I
> could just put in a tiny pushbutton that had to be depressed as well as
the
> desired command button each time a command was sent. That approach makes
it
> a two-handed operation, whereas a slide type ON/OFF switch could still be
> worked with one hand.

<<My fob needs to be reprogrammed every time the battery is changed. I
would imagine yours is similar.>>

I inadvertently did the experiment that Ian first suggested because when the
fob is popped open, the battery goes with one half, the circuit board with
the other.  After being disconnected for several hours, it still locked the
car (I looked out the window to see the lights flash).  This is a TRW remote
for a 2002 Chrysler Grand Caravan.

<<Disconnecting the battery would have the same effect. It would get
very annoying to have to reprogram the fob every time I wanted to get
into the car.>>

Yes, that would be a deal-breaker.  That's why I suggested to Ian that I
would look for a way to insert a second switch into the circuit that did not
affect the trickle current going to the IC.  That should be pretty easy
since it's an open circuit anyway.  Adding a second switch would just mean
that both had to be pressed simultaneously.

Thanks for the caveat, but as far as I can tell, my unit doesn't have a
sophisticated fob.  Perhaps that's because the keys have RF immobolizers
built into them and the security is "concentrated" at that point.

<Try wearing pants that aren't so tight when you keep the keys in your
pocket.>

It's not only pants, it's holding them in your hand with all the other
things your hands do upon exiting a vehicle or even throwing them in a
purse.  The damn buttons are just not "stiff" enough to resist erroneous
activation.  Bad design.  From a carmaker.  Who would have ever expected it?
(-:

--
Bobby G.