Need help designing an automotive engine run detector.

The whole idea is to keep all connections under the engine compartment. Installation time and complexity increases significantly when you pass wiring from the engine compartment into the passenger compartment through the fire wall. Most people won't do it. I majority of people who attempt it do it wrong. It takes a mechanic much more time and costs you more money. We sell another non-related under hood product. Many major chains (Goodyear, Firestone, Canadian Tire, others) will not carry our product due to concerns about passing wires through the fire wall.

I'm not sure you can say in ALL instances that an ignition signal would be easily accessable under hood. It seems like the obvious solution but when you really dig into it, may not be....

Yeah, that was my point. With all the surgery I'd have to do in the passenger compartment to get to the cigarette lighter wiring, the requirement to do so would be a deal breaker for me. So the lighter circuit is out of the question.

By the way... the Speed channel used to advertise a gizmo that appeared to be an accelerometer-based performance monitor. I think it was called a GTech Pro or something like that.

One of its advertised features was shift lights. That would imply that their engineers had figured out some way of directly or indirectly measuring engine RPM. Since its only connection was a cigarette lighter plug, they must have picked up some sort of signal from the DC feed. Maybe you could look it up and see if you can figure out how they did it.

Another thought was your installation location. You mentioned that you're installing your unit very close to the battery. Well, that battery must be acting like a really great filter that's killing any signals that might be of use to you. Maybe if you could move your installation downstream a bit, you'd have enough inductance between your power pickup point and the battery that you might have more useful power line noise to work with.

Good luck!

Tom

PeterD wrote in news: snipped-for-privacy@4ax.com:

Older Ford alternators also had an AC output to drive the electric choke, on carburated engines.

"Genset" is a contraction for "generator set". A "standby" genset is one that just sits there, not running, until there's a power failure, at which point it starts itself, and a transfer switch switches from the (now dead) mains to the generator. They're used a lot at places that absolutely, positively have to have power, like hospitals.

Hope This Helps! Rich

Try a scope on the battery and see what you find. you can get rev. counters that get the engine speed from the alternator noise in the cigeratte lighter socket

-Lasse

Rich Grise wrote in news:pan.2007.10.10.16.31.35.543101 @example.net:

They use an RPM detector and oil pressure detector, the former from the generator output, the latter from the engine wiring harness.

That's probably what OP was looking for, but he/she is a google-groupie, so has probably abandoned the whole thread by now.

Thanks, Rich

I've done this. The problem I see is signal levels and consistency from one vehicle to another. For instance, in my vehicle a 300mV pulse is generated every time a plug fires. The pulse is just over a nanosecond wide. The noise floor from all kinds of other crud on the power buss is about 50 to 100mV. Longer wire runs (away from the battery) only increased signal level marginally.

The REAL kicker, and unltimate downfall to this line of expreimentation, came when I turned the radio on. The crud generated by the vehicles audio amplifiers FAR swamped any other signal I was seeing before. Current drawn from the amps is modulated by the audio signal. My proposed circuit could trigger off this. Not bad if you assume everyone listens to their radio while the vehcile is running. However, I've been tailgating at football games before and have left the radio on "blairing" sportscasts for an hour at time with the vehicles engine off. Or, I may run the radio with engine off while i was my car. I would hate to have the proposed product running during this time frame.

Ge0

On Mon, 15 Oct 2007 08:43:46 -0700, Gerbermultit00l wrote: ...

Connect it to the oil pressure idiot light.

Good Luck! Rich

Generator auto starts use a connection to an oil pressure sensing switch to detect engine running. You know, the switch that is closed when oil pressure drops below 4 psi. I know this because I have several auto start generators.

A lot of cars use only a gauge type sensor (but be careful, some gauges, some Ford and Dodge pickups come to mind, are fake lights where the sensor is a switch but it closes with pressure, but you could still use that). So if they only have an analog sensor you'd have to y off and add a switch type sensor.

Jerry Steele

If you're going to all that trouble, why not just take the RPM directly off the flywheel sensor? No need to worry about the battery state or ratio between the crank and alternator pulleys.

krw wrote in news: snipped-for-privacy@news.individual.net:

In the first place,WHY does anyone NEED an "engine run detector"?

doesn't the dashboard give any indication of that? (besides your ears and seat-of-the-pants)

Remote start/warm-up ???

You know some places in the world get cold ;-)

...Jim Thompson