Common Source of Automotive Vibration? 1

[rajin12]

For any vehicle, where would you find the highest vibration?

I'm testing out an accelerometer that will be used to wake up electronics.

 

[FeX32]

If everything else is balanced then the engine is always a major source of cyclical vibration.


Fe

 

[IRstuff]

Generally, vibrations are either self-induced ones, like the engine itself, or from the environment, like the road. The frequencies will be different, as will the amplitudes.

TTFN

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[PriamEngineering]

top of the cylinder head (assuming vertical in line engine)this will capture the firing induced acceleration

http://www.priamengineering.co.uk

 

[IRstuff]

Overall, this seems a bit off. Why not just look at whether the tachometer has a reasonable output, or even just that the ignition switch is ON?

TTFN

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[GregLocock]

Might be an idea to tell us exactly what event you need to detect, and whether you can talk to the many existing sensors in the car.

Cheers

Greg Locock


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[ivymike]

If you just want to wake up the stereo system when someone is getting ready to leave, look at the door switch position or the striker vibration.

 

[rajin12]

I'm trying to make a test setup where my chemical sensor will make a measurement a certain time after the vehicle has moved/or has not moved. But I want this to be portable for different vehicles w/o having to mess with the vehicle electronics.

For vibrations in the engine, should I expect things like timing belts to remain rpm independent as opposed to cylinders?

As for environment induced vibrations, what components would likely be affected? Or does the suspension system dampen everything out?

 

[IRstuff]

"timing belts to remain rpm independent as opposed to cylinders"

Huh? A well adjusted timing belt runs at the same rpm as the engine, since it's intimately connected to it.

"what components would likely be affected"

There really ought not be any, since vibration reduces life. There's a general vibration environment, and as mentioned a couple times already, the engine itself is a large part of that.

If you don't want to alter the car, then why not use a clip-on spark plug wire sensor? Not only will you get an indication of engine rpm, but also timing.

TTFN

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[rajin12]

Ahh, I will look definitely look into that.

 

[GregLocock]

Strictly speaking the car can be moved without the engine running, and the engine can run without the the car moving. I admit these are not very common but if you want an ironclad method of measuring motion independent of the cars systems then you need GPS.

Cheers

Greg Locock


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[ivymike]

the engine running w/o the car moving is very common...

 

[TheBlacksmith]

the engine running w/o the car moving is very common...

Yes, around here we use the oxymoron "rush hour!"

 

[IRstuff]

Ain't that the truth.

Nonetheless, the "chemical sensor" might still be able to make a decent measurement, with the engine spark sensor doing a minimum of processing to validate a time series of ignition pulses as being consistent with normal driving. Presumably, measurement system will be making measurements over the course of days or weeks, so a singular instance of odd behavior shouldn't mess things up too much. If these erroneous events happen too often, then the car chosen for measurement was a bad choice.

TTFN

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[FeX32]

Thought.
If the engine is not engaged to the transmission and drivetrain and it is "revved" would it not exhibit more vibration than the situation where the vehicle is driving and we rev the engine?
I never thought of this before, just a thought.
The inertia of he drivetrain components may change the amplitude and or dampen the engine case vibration.


Fe

 

[patprimmer]

If the car has ABS, the wheel sensors could sense the car moving so long as the car had not been jacked up and placed on a separate device like a tilt bed truck or a vehicular ferry.

Wheel sensors and spark plug sensor combined would sense engine running and wheels turning and that covers all but the most bizarre circumstances, like sliding along an ice covered road with engine running and brakes locked.

Regards
Pat
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[MikeHalloran]

Simplest solution, perhaps not 'smart' enough for this application, is measuring voltage at the cigarette lighter, excuse me accessory, socket.
When the voltage goes from 12 or less to 13 or more, the engine has started, and chances are the car will move soon.
When the voltage goes back down to 12 or less, the engine has stopped, and chances are the car is not moving.



Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

Mike. That is an astoundingly simple test for engine running and from the cabin with not one spot of soil on the hands.

A simple accelerometer like in fancy smart phones might detect motion to a sufficient degree.

Regards
Pat
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[MacGyverS2000]

Or if it's my car, simply determine if there's voltage at the cigarette lighter... if not, the engine is off.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[ivymike]

On my Scion that would tell you whether the ignition switch was in "on" or "acc" positions but wouldn't tell you about the status of the engine.

On my Explorer that would tell you that you'd found the hole...there's always voltage in there if nothing's broken.