Ways to detect shock such as an accident

Hello all!

So I am doing a project with my friends about detecting a car accident. We have handled the part where we are required to send co-ordinates at which accident has occurred. But we are stuck on the basic requirement of the project- How to detect the accident ?!?!
After some googling, we came across the vibration sensor module SW-420. But this sensor doesnt seem to be suitable for us. You see cars are more or less vibrating while running.
So what are the alternatives to SW-420? How about accelerators?

Thanx!

Perhaps research what sensors are used for airbag deployment?

Can the on-board bus give a signal when the airbags deployed?

(edit: which is a bit like what Paul__B said, but using the sensor that's already there.)

Paul__B:
Perhaps research what sensors are used for airbag deployment?

How about IMU sensors like MPU 6050?

noob_geek:
After some googling, we came across the vibration sensor module SW-420. But this sensor doesnt seem to be suitable for us. You see cars are more or less vibrating while running.

The module has a sensitivity adjustment. Could you not crank it down to ignore low amplitude vibrations and just respond to large signals, like hitting a wall?

dougp:
The module has a sensitivity adjustment. Could you not crank it down to ignore low amplitude vibrations and just respond to large signals, like hitting a wall?

The SW-420 "sensitivity adjustment" controls the sensitivity to duration of a vibration event, not the amplitude of the vibration event. The SW-420 does not detect vibration or acceleration amplitude except in the binary sense that it is above some threshold inherent in the sensing element.

To detect acceleration amplitude one needs an accelerometer (e.g. ADXL337) or IMU (e.g. the aforementioned MPU 6050).

I am anxious to see the results of the first 10-12 tests.

Paul

Yes I’m looking forward to seeing how you test this .
There are switches used to cut the fuel pump that respond to impacts - google is your friend

hammy:
There are switches used to cut the fuel pump that respond to impacts

Honestly speaking, I really dont want to sniff the CAN bus or "under-the-hood" systems. A few years back, I tried to come up with a alco-lock system and it was a nightmare. Needless to say, just abandoned it.
Thats why I am looking for sensors that can do the job without any pain.

And about using an accelerometer or IMU to detect sharp accelerations, as was mentioned thrice already, you being one of them?

A piezo disk can tell you the severity of a shock. You'd need more than one and have to figure out how to tell a pothole from a paint swap but that goes with anything but a passenger with a button.

For demonstration purposes, a tilt switch works just fine.

Sudden acceleration/deceleration will move the ball and trigger the switch.

In fact that is the basis of more car crash sensors, they add in mechanical dampenin around the “ball” and if the ball touches a contact.....

Potentiometer with a weighted lever would work also.(pendulum)

How about a sensor from a junk yard? Not all cars in a junk yard have been crashed - problem might be finding where it is mounted and the interfacing

Will a tilt switch that the whole vehicle momentum has to change to swing tell a hard braking maneuver from a fender crumpler that does not cause much total change?

I live up a steep hill. The road is tilted…

Why I suggested piezos is that you can measure shock vibration with them, and you’d still need several at least.

Pendulum/pot could be set to read only maximum ( say 180 degrees at rest, 90-100 degrees collision)

Don't think the hills are that steep.
Perhaps a bit of damping to allow for braking on the steep hills.

When it can only detect a head-on crash then will it be right?

I’m looking at the difference between all sorts of bangs and normal operation including pothole bumps. A tilt switch involves accelerating the whole vehicle, as you point out must be set maximal.

Perhaps you may detect a collision in the most simple and reliable way - a switch or a circuit beaker in the crumple zone?

If the car's bumper is displaced - it breaks the circuit and lets your device know of the damage?

Also noise is tell-tale sign of a collision. Metal car frame should be an efficient conductor of sound.
You may use contact mics to detect a crash.

Yes. Often piezo disks are sold as acoustic instrument audio pickups. Get them cheaper in bags of 10.

You can pin-safe a piezo with a diode and an optoisolator to detect press only or use 2 optos to press and release.

On Youtube is a video named Ants, Amplified. It demonstrates the sensitivity and fidelity of ants walking on a good quality piezo disk resting on rough stone and amplified about 10K times with a pro quality amplifier. It's a bit eerie.

voice recognition ? I was in an accident once and you would know by the language !

also, you could send a signal just prior when the system encounters "hey bubba, hold my beer and watch this"

as for actual technology :
Analog Devices