Suggest a motion sensor Please

[sougata]

Hi,

I need to design a simple motion sensor that would be mounted on a railway coach. Basically there is a LED billboard mounted on the outside of the coach which needs to be turned-off (to enhance LED life) when the train is in motion. When the train is moving slowly or stationary I need to turn on the billboard.

I have no previous experience. I need suggestion on choosing the sensor.

Right Now I am going through this thread http://www.picbasic.co.uk/forum/showthread.php?p=33853

[skimask]

Hi,

I need to design a simple motion sensor that would be mounted on a railway coach. Basically there is a LED billboard mounted on the outside of the coach which needs to be turned-off (to enhance LED life) when the train is in motion. When the train is moving slowly or stationary I need to turn on the billboard.

I have no previous experience. I need suggestion on choosing the sensor.

Right Now I am going through this thread http://www.picbasic.co.uk/forum/showthread.php?p=33853

Put a magnet on the wheel, trigger a timer on a PIC...

Fire an IR LED at a certain angle at the track, put another IR detector downstream a bit, watch for changes in the intensity of the IR pulses...

Put an IR LED and detector pair in the doorway...each pulse resets a 5 minute timer on the PIC...

Put a microphone next to the roadway...at a certain noise level, you'd know you were going above X mph (kph, whatever), and shut the sign off...

Have the person running the coach flip a switch...

Hire somebody else inside the coach to flip a switch...

Buy a GPS module and watch the lat/lon output...when the position's delta is below 'x', turn on the billboard...

Buy a pitot tube and connect it to a pressure sensor...then connect that pressure sensor to the A/D input of a PIC...at a certain point, pressure is too low, coach must be moving slowly and/or stopped...turn on billboard...

Do the same thing as that other thread with a small metal ball on a chain in a metal can...have that 'intermittent' connection trigger a timer for the billboard...

Buy an ADXL330, use the X/Y outputs to calculate speed and turn on the billboard according to that number...

(If this coach is on a railway) Drag a small wire connected to a lever switch, when the wire hits a crosstie in the roadbed, it will trigger the switch, and therefore trigger a timer in the PIC...

And to think...all those ideas (crappy as they may be), came to me at the same time it took me to type this out...

[T.Jackson]

Keeping tabs on the amount of current that the train is drawing would suffice in providing an accurate vref that's directly proportional to movement. Use a hall effect sensor to monitor large amounts of current. They're relatively inexpensive and accurate too.

Best Regards,
Trent Jackson

[sayzer]

http://www.picbasic.co.uk/forum/showthread.php?t=5820


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[sougata]

Hi,

Thanks for the replies guys. I am going through the datasheet of accelerometers and seems to be the best option. I hope it is available readily. I am only supplied with a DC supply and nothing else. So cannot probe any other signals from the railways.

Sayzer the thread you pointed is the same that I looked up. But the links are different.

http://www.picbasic.co.uk/forum/showthread.php?t=5820
http://www.picbasic.co.uk/forum/showthread.php?p=33853