I am looking for a sensor to reliably determine the state of motion of a car (passenger, van, forklift, tractor).
I will not disclose the nature of the project at this time but a similar sensor system could be used to activate a log of travel hours or send a GPS position report on arrival and departure from a destination.
First priority is low power, it must trigger a micro-controller (in deep sleep) only on motion start and stop, my complete system will operate on 2 or 3 coin cells for long periods (not wired to the vehicle, relocatable, cheap).
Second priority is 0% false detection of motion at the cost of response time.
Response time of half minute is optimal, 5 minutes is about the limit.
I require a signal edge on the state change from stationary to in-motion and vice versa and knowledge of which state the car is in.
I have considered trembler switches using springs, ball bearings, conductive liquids (not Hg). Also magnetic field vector sensor to determine rotation of vehicle, might not detect short movements. An accelerometer to sense motion might false on loading activities.
Passive sensors could interrupt from motion. Magnetic and acceleration sensors would need to be polled (every 30 seconds) to determine if changes have occurred. An alternative would be to use a combination with the trembler switch triggering the other sensor to confirm movement and avoid false motion event.
Changes in engine or ignition status, ambient lighting, noise level, occupancy, loading, unloading, construction site proximity must not cause false motion state.
Also intermittent motion in a parking garage, fuel queue, traffic lights or traffic jam should maintain a reliable motion detection.
My current idea is to have a sensitive trembler switch with asymmetrical filtering and long time hysteresis to change.
Are there standard sensors types that are used for this or that would provide me with a simple output I could condition?