Movement sensor

[Lotondo]

Hi all,
for my pic project I need a movement sensor (no P.I.R)
to be placed in a car.
It will turn on the pic as soon as the car moves.
I tried to search it with google but nothing good came out.
Anyone already used this kind of device ?
Thanks for help and advices

Bye
Lotondo

[mister_e]

when you say 'when the car move' in which range...mm, Cm, kilometer?

Does the engine have to run, etc etc etc.

I'm thinking of the car V.S.S. signal

[HenrikOlsson]

Hi,
If it's for an alarm system, aiming to sense if someone is tampering with the car you could use an acclereometer. Or perhaps something from these guys:
http://www.assemtech.co.uk/assemvibration.asp Or a simple steel ball suspended in a wire hanging inside a tube. When the car moves the ball starts swinging and makes contact with the surrounding tube - trig whatever... (Like the old pinnball machines tilt sensors)

If it's not for an alarm system then I'm way off (except for the accelerometer)

HTH
/Henrik Olsson.

[Lotondo]

Mister_e,

I also thought to use the + wire from the ignition key lock but
it would not be so easy to get it and it's not always located
at the same place.
I thought it should be something like a mercury switch or a
metal ball etc.
Let's say if you push the car it should be already enough to switch
on.
My project is a gps data recorder and the switch will avoid the pic
to stay on.

Bye
Lotondo

[mister_e]

there's still the microwave(field) sensor option used in MANY car alarm such as DEI/Viper 508D sensor.. wich cause more false alarm than anything else so far...

It's as good as using a PIC internal osc... it shift with temperature, gas pricing, wind direction, humidity etc etc etc...

[mister_e]

Mister_e,

I also thought to use the + wire from the ignition key lock but
it would not be so easy to get it and it's not always located
at the same place.

I hate that suggestion but you could still tap your wire to the fuse box. Professional installer will tap their wire directly to the ignition switch. It's always at the same place.. but of course never the same color depending of the car Brand. Not as this hard....

I thought it should be something like a mercury switch or a
metal ball etc.
Let's say if you push the car it should be already enough to switch
on.

Yeah those mercury switch could work, but if a van pass close to the car, it may trig a false event if not properly installed. Another thing... if the car is parked in a not flat area (few degree) the sensitivity will be affected as well.

In the past we used that kind of switch in car alarm, i debugged a lot of faulty installation and also i remove tons of them to replace with usual shock sensor... which don't apply in your specific case.

I will prefer a ignition switch + maybe a VSS signal combination... yeah the Vss signal is sometime a pain in the LALALA to find as most car cluster haven't that signal directly at the cluster connector but computer mixed signal...kind of data line.

OBD ic?... i don't think it worth the price if you just need a VSS signal.

Easier to read a Tachometer signal... if you got a tach signal... at least the car is started. This said, you just need to detect a few HZ frequency. You can take the signal from the Car ignition coil, or injector. For Diesel, you might need to read the voltage at the alternator output OR create your own tach signal with a Hall-Effect sensor...

Nothing is perfect

[Bruce]

If this is something that will only be activated when someone is in the drivers seat, why not use a simple pressure switch in the drivers seat?

[mister_e]

or the brake switch?

Or detect if the battery voltage go under 12 volts for a few hundred milliseconds (that what OLD remote starter used in the past to see if the car had started)

I could say, use the lighter plug.. but some are connected directly to the battery.. so...

[sayzer]

1. Attach a weight on a pot pulling it down to ground. When the car moves and is moving it will change the pot reading in small steps by moving it back and forth. When the car is not moving for sometime, say 30secs or 60 secs. etc, then you will read a constant pot value AND know that the car is stopped.

OR
2. Short the wiper so that driver will always know that the GPS is running.

------------------------------

[Lotondo]

Thank you all for the good ideas.
I'll try to find the best one from them.

bye
Lotondo

[Ron Marcus]

Marty Kaiser made a motion control switch that can't be beat for simplicity. He took a short length of stainless ball chain (like a light switch chain), and hung it in a metal box similar to the suggestion above. The PIC would sense a change of state which would happen if the box/tube was jiggled even a little. For GPS, a vehicle passing would just record another way point. For an alarm, I would count the number of changes in a 5 second time, and if it exceeded a certain amount it would trigger the driver seat detonator ,tear gas grenade, or wake the trained Rotweillers in the glove compartment.

[Joe S.]

Mister_e,


Let's say if you push the car it should be already enough to switch
on.
My project is a gps data recorder and the switch will avoid the pic
to stay on.

Bye
Lotondo

Hi Lotondo,
The alarm industry already sells motion / Vibration sensors which are very sensitive, my noisey car sets them off all over town They work by suspending a little magnet over a coil or hall effect sensor on a silicon rubber band. you could use one to "wake up" your pic which could then check the vss or antilock brake sensor and go back to sleep. I really do not see why you would need to go so low power mode given the massive power reserve a car battery contains, I am pretty sure you could power a pic for many months without killing the battery. Your car's computer has a constant draw and yet the battery lives a very long time.

[Pic_User]

Omni-directional Tilt and Vibration Sensor
SQ-SEN-200
draws as little as 0.25uA of continuous current
This site even has PIC BASIC Pro Code:
http://itp.nyu.edu/physcomp/sensors/Reports/SQ-SEN-200

Manufacturer:
http://www.signalquest.com/sq-sen-200.htm