Which type(s) of sensors for a project like this

Folks go way fast on my street. I would like to (INEXPENSIVELY <$100) make a way to make a “speed trap” to find out just how fast these cars are going and go visit with the specific perpetrators and show them the data.

I assume I could set up some type of sensors that would get the front of the vehicle at point A, measure time to point B where another sensor picks up the vehicle. Nothing perfect, because I can go buy a hand held device for just under $100.

I have an Arduino Mega board, I have a couple Propeller Dev boards.

What should I use for sensors…daytime use? Street is about 20 feet wide, I haven’t measured.

Any pre-existing C, C++, or Spin programs out there already made for this that I could modify? I guess biggest cost would be the sensors, right? Part numbers would be really awesome too.
Thanks

That is not easy. Can you buy a (used) velocity speed gun and try to interface that with the Arduino ?

Folks go way fast on my street. I would like to (INEXPENSIVELY <$100) make a way to make a “speed trap” to find out just how fast these cars are going and go visit with the specific perpetrators and show them the data.

While a technically interesting project, I question what the speeders will think of your data when you present them with it? Are you assuming that they are not aware that they are speeding (or don’t care) and will thank you for your concern as they review your data?

you could also ask the police to install a speed camera?

Ya, well they put the thing up that shows them how fast. It does no good. I would rather just be able to just talk to them, as neighbors and leave the police out of it, they are a bunch of fools that want to be swat team cops.

J

If you can find one of the Hot Wheels Radar Guns, you can hack that:

http://www.instructables.com/id/Radar-Gun-Hacked!/

Unfortunately, the price is about $100.

http://www.amazon.com/Mattel-J2358-Hot-Wheels-Radar/dp/B000EHLB0M

For that, you can get a real (cheap) radar gun, too.

http://www.amazon.com/Bushnell-Speedster-III-Radar-Speeds/dp/B00439V84G/ref=pd_sim_sbs_t_2?ie=UTF8&refRID=11R1T6Y0CCND9YTXHSMN

Parallax sells a Doppler radar detector, (can get it from Adafruit, I believe) of the type used to open supermarket doors, for about $30. I am using one in a motion detection system, but I am only interested in detecting motion, not speed. Its output is a pulse train, which in fact is dependent on the speed of the object being detected. If you hook it to an Arduino, and count pulses per second, you might find it was adequate for the job.

Good luck. I'd be interested in what you discover.

John Doner