AIGD module wasRe: Need help designing an automotive engine run detector.

Jeff Liebermann wrote:
On Tue, 09 Oct 2007 20:11:04 -0000, Gerbermultit00l@xxxxxxxxx wrote:


On Oct 8, 10:38 pm, Jeff Liebermann <je...@xxxxxxxxxx> wrote:

Bad idea. You're bypassing the entire fuse and breaker protection
mechanisms in the vehicle. You would need to attach a fuse directly
to the positive terminal of the battery, a non-trivial exercise.
You're worried about the GUM (great unwashed masses) doing a proper
install, yet you don't seem to be worried about the same person is
going to get a wrench between the positive terminal and ground, with
the resultant smoke, fire, burns, and litigation.


Bad idea?


Well yes. It really depends on who does the install. If it's the
clueless bozo that you're apparently you market audience, anything
that requires tools is a bad idea. Horror stories on request.


Hmmm, I wonder how the high powered car amplifier market
gets by. They sell millions of those things a
year. Perhaps because they do not actually supply the wiring?


Most are installed by auto electronics shops (and then cleaned up by
auto electric shops after the wiring harness gets torched). It can be
done successfully by anyone who actually follows the instructions, but
your target audience apparently doesn't qualify. You're correct.
Directly wired to the battery.
<http://www.caraudiohelp.com/how_to_install_a_car_amp/how_to_install_a_car_amp.htm>
See item #7 on fuse location.

Incidentally, if you want your worst case nightmare for do it thyself
automotive electronics, see:
<http://www.mp3car.com>
in the "Show off your project" forum section:
<http://www.mp3car.com/vbulletin/show-off-your-project/>
Some of the installs are rather marginal bordering on dangerous.
Others are really impressive works of electronic artisty. The
majority seem to survive without fire or an extended vehicle warranty.
I'm shopping for new wheels and plan to install a computer in roughly
the same manner.


Similar case to the electric hedge cutters. Ever
see one lately with a corded pigtail for power? No? That's becuase
some fool probably cut through the supplied
pigtail, sued them, and won. So, to counteract, the guys making the
hedge cutters molded a plug into their handle.
Now if the fool cuts through the cord, they need to sue the extension
cord maker :).


You're stretching it a bit. Between about 1973 and 1985, my hobby was
product liability litigation. It was a hobby rather than a profession
because I carefully avoided most pitfalls and traps in the products I
helped design. I would collect horror stories from the news and trade
journals and bring them to meetings. That would inspire the others to
be VERY careful. Anyway, if you have any relevent horror product
liability horror stories, please make them relevent to user installed
automotive electronics. Hedge cutters aren't even close.


I'll let our lawyers determine if we supply wiring, fuses harness to
connect to VBAT, etc... Or if we play it on the safe side and make it
the customers responsibility to supply these goods.


Actually, the lawyers don't decide anything. They advise.

As I understand it (possibly wrong), dumping the responsibility on the
customer, where the customer is forced to make a decision based on
insufficient information, is a loser in court. The customer merely
has to say that he did not understand the instructions and they're off
the hook. It's your responsibility to insure that the customer cannot
do anything wrong, cannot misinterpret, and cannot injure themselves.
Consult and attorney to be sure.


Yep. That's the worst case scenario for electronics. Roughly -40C to
+105C. Don't forget about water proofing and high voltage spikes on
the power lines.

I design underhood electronics to survive all know electrical system
faults and SAE-J1113-11 transients at +125C


When activated this product will draw about 5 amp.

75 watts? Where are you going to empty out the heat?

Product design and packaging will take this into account.


Ok, I have a design question. It draws 5amps. How are you going to
turn it on and off or is that the purpose of the engine run detector?
If this is the case, how are you going to prevent Joe Sixpack, from
placing a boom box on the air filter, and playing race track sound
effects CD's at full blast, causing your engine sound activated
contrivance to falsely activate? No answer required, but at least
think about the many ways in which such a system can fail.

Incidentally, does this have to work in a hybrid? They don't make
very much noise when running on battery.


I didn't want to run additional wiring. However, if I have to, IGN
would be my 1st choice.


Well, it does have the benifits of simplicity. However, once you have
a microprocessor to abuse, engine run detectors can be made as
complicated and elaborate as the software will allow. Complex
algorithms, that accept input from multiple sensors (sound, vibration,
IR, acelleration, etc). We're not fighting for every byte of RAM or
counting CPU cycles these days.


Thanks for your feedback Jeff.


Glad to be of assistance. Incidentally, I spent 9.5 years designing
consumer marine electronics. It's not the same as automotive, but
it's close enough with the added enjoyment of a corrosive environment
and a semi-intoxicated operator.



Have a design concept for non-contact and low power, could be battery powered. automotive ignition detector uses non contact radiated engine or electric motor contractors spikes, and a coincidence detector. PLease contact me for commercial versions of this module!

Marc
Best regards and happy designing

marc


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