> Second, I can't help you directly with the gasoline
> powered model car, apart from a basic suggestion.
> My friend had a small-scale RC car using a gas motor,
> it was about 18" long and did 40mph (real mph) and
> was rather scary. My suggestion would be to take
> care designing the throttle and brake systems to
> be fail safe, so in the event of ANY failure the
> throttle closes and the brakes are ON. Having seen my
> friends car get out of RC range and crash into things
> fast enough to break a human leg and destroy the
> car, this is pretty important...
>
> Maybe you could send a "good" code constantly to the
> throttle and brakes, and the moment this code fails
> the onboard PIC (watchdog?) etc goes into "safe"
> mode. It's surprising how often an RC vehicle gets
> bad info or loss of info from the controller. :o)

        Considering the size and weight of the car safety has been one of my number
one concerns. I actually have a few layers of safety. First off the throttle
and brake are handled completely seperately, and both will default to a safe
status if a pulse from the receiver isn't received in the last 60ms (safe
for the brake being completely on and safe for the throttle being completely
off). Aside from this the steering system will default to fully left (or
right, haven't decided) in case of loss of contact with the transmitter, so
if everything else goes wrong at least the thing will go in tight circles
instead of a straight line.

        I might also add a redundant kill switch with a second transmitter and
receiver, the only problem, and this is something I was planning to ask, is
how do you stop a gas engine remotely? I thought about disconnecting the
spark plug but how would I do that considering the voltages involved?
Cutting the fuel flow is a second idea but my experience with two stroke
engines is that they keep running, without any fuel flow for at least 30
seconds, long enough to cause damage. Anybody have a better idea? Thanks,
TTYL

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu