Can anyone think of a simple (and cheap..) independant sensor that can accurately sense when a vehicle is moving and when it is stopped - eg is there something GPS related that will give some kind of signal (not interested in any kind of data apart from movement) or is is there something even simpler that I'm missing??

Some kind of tilt switch, or inertia sensor (used on old fuel injection cars that shuts the fuel pump off if you have a bump).

Some car alarm add on units sence movement should the car be towed away or jacked up as well.

Whats it for? , then we might be able to suggest something more appropriate or another way of doing it.

Do no if locost but ultimate car security
do tracking devices & send texts to your phone
if it helps
cheers
steve

abs wheel sensor

Well the idea is for a simple stand alone unit for truck drivers working with a tachograph so they can idependantly tell how many hours they have actualy been driving (ie vehicle moving) not driving (ie vehicle stopped) and the break they are entitled to - not sure of the legal whys and wherefores of tachograph driving yet btw (and wont bother finding out if the basic idea is unrealistic ). It's an idea for a project as part of a MSc in computer aided product design that I've somehow found myself on.......

The ABS sensor sounds like the best option for true movement, linked to some sort of counter or even a time clock.
The only problem then is you've got to break into a safety system of the truck wireing, unless you could fit another.

I suppose it'd be easy to cheat but a simple one would be a switch on the throttle pedal, your assembly could clip onto that, in usual operation unless your moving along you've no need to be pressing the throttle pedal!

Or a link into the trucks speedo, whenever its not on zero something counts.

Or I suppose for simplicity you could go for the opposite path of thinking and connect something to the brake light and handbrake, to tell when there not moving!

Don't some electirc speedo's work off the propshaft ?

[Edited on 25/2/06 by beefy]

Hall sensor on the propshaft ? wouldn't need to interfere with any safety systems and cheap

It could be coupled to a shaft rotation relay, as often used in machinery, it senses rotation of the shaft by looking for an impulse at a preset interval.If no input it times out and gives an output from a change over relay.RS list a few versions that may work.
Paul.

quote:

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Originally posted by rusty nuts
Hall sensor on the propshaft ? wouldn't need to interfere with any safety systems and cheap

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Tachographs all ready show when vehicle is stopped and moving, what it can't do , is switch the use from just stopped, not travelling at any speed, to driver resting, that's their downfall it's usually a manual switch the driver has to turn

Jason

what kind of distance/angle (and through what) can a signal be picked up from a hall sensor? - bearing in mind I would only be looking for something in the order of 1 road wheel rotation as a trigger? Would it be possible to design something to clip on the road wheel (along the lines of the plastic things fitted on wheelnuts to check for tightness) and get a stand alone unit in the cab to pick up that impulse - or would it need a sensor attached to the wheel arch (or similar) to pick up the wheel rotation impusle and send it to the device in the cab?

ahh indeed Jason, that was the ex truckers idea ie to have something cheap and simple to tell the driver how long he had actually been officialy driving and therefore when a break was due - loads of things to sort out with it obviously but if there isn't a cheap and simple way of accurately telling if the vehicle is moving the whole concept is f**ked from the begining

Although a truck may be stationary ie not moving do traffic holdups the driver is still classed as driving,unless he pulls over and sets is tach to rest then he can only log this rest period if its 15+mins

If the engine isn't running the driver can't be driving. Perhaps some means of timing how long the engine has been running would work?

Driving regulations dont work like that. If driver is not in rest mode then any time behind wheel wether stationary with or with out engine running is still classed as driving . Many a H.G.V. driver been done by ministry for this.