From: dave vanhorn <dvanhorn@CEDAR.NET>
>>> The conclusion I've come to here, is that I don't want
>>> a microprocessor controlling my chute.
>>> This sounds a whole lot like the oldest bad idea in rocketry,
>>> the remote-controller launcher.


Remote control rocket launcher (Estes variety anyway :-)) is OK if
you have a person on a "deadman switch" (bad choise of terminology
here ;-)) which MUST be operated when the computer says its time to
fly. Computer can tell you when IT thinks its almost time and you can
have casting vote from slightly before launch time on.

In the case of a manned parachute the equivalent live-man is always
on hand ;-)

>Being a first responder, I can tell you that there is a real
concern, and
>several incidents have happened already, that the airbags don't
always
>deploy in a crash, but will deploy afterward, during the time you
are
>working on a patient. They tell you loud long and often to watch
where you
>set your gear in the car, because the airbags can trigger and shove
your
>gear into someone's face.


Philips have a ?new bus which is designed for use with airbag squibs,
belt tensioners and their ilk.
It sends power and signals together. It has 2 data rates - usually it
runs at the slow rate and squibs know they are not allowed to fire.
Only when they are being clocked fast will they fire (IF they are
sane, anyway). This still won't protect you from an air-bag which has
been triggered but failed to mechanically fire and is "smouldering".
Also, central computer logic still needs to be either intact or dead.
(Personally, I consider a 5 point harness, a helmet  and a full roll
cage makes MUCH more sense than airbags. Very few rally drivers die.
Some do.)

The clocking and signalling is somewhat clever.
AC is sent to the bus.
Positive half cycles are clocks and also provide power.
Negative half cycles are present only for "0" bits.
Effectively you have a ternary system with positive peaks always
present and negatives sometimes present.
Clocking and, very importantly, Power feed, is never lost regardless
of how many "0"'s are sent consecutively.

I intend to look at a similar scheme for a low speed home remote
telemetry system I am playing with.

Has anyone seen this bus in action?

regards

        Russell McMahon