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Proximity Sensor/Transmitter

Proximity Sensor/Transmitter

Proximity Sensor/Transmitter

(OP)
Does anyone know if the following device exists?

1) Will sense the presence of a item, such as a car.
2) Will then transmit this information wirelessly to a receiver up to 1/2 mile away.
3) Be self powered.

If yes then where can I find one?

RE: Proximity Sensor/Transmitter

google for "wireless driveway detectors".

There are dozens of them. Up to miles!

Keith Cress
kcress - http://www.flaminsystems.com

RE: Proximity Sensor/Transmitter

You might want to consider an inductive RF Id tag.  Tag is self powered and depending on the reciever setup I think you can sense within about 25-30 feet.  Then you coud wirelessly transmit from the reciever station.  Just a thought.

Rich.....viking2

Richard Nornhold, PE
http://www.ovenind.com

RE: Proximity Sensor/Transmitter

One question, then, boils down to whether the "item" is cooperative, i.e., you can modify it to meet your requirements stated herein.

Another question is whether by "proximity" you mean actual distance, or simply existence of the item within a certain boundary.  A corollary question is whether the presence of the item outside of some boundary is allowed to be detectable.

TTFN

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RE: Proximity Sensor/Transmitter

(OP)
Thanks for the ideas guys.
What we are actually trying to do is manipulate traffic flow on our property in real time, both day and night.
The thought is to sense the presence of vehicles as they come close to what are effectively traffic lights. We would like to count the number of vehicles approaching the intersection from all four directions and relay this information in real time to a processor. The processor then decides which traffic flow is most important, based on criteria set by engineering.
We were thinking of sensing oncoming traffic from about a mile away, and hopefully be abale to determine if the vehicle is moving or is stationary. (ie if stationary then it means there are many vehicles travelling in that direction). There will probably be multiple sensors with their density increasing as you get closer to the intersection, constantly generating data that can be processed.
Ideally we would like to drop a sensor into the road and have that sensor transmit its' data to a processor. It would have to be inside a weatherproof box and be easily accessable to change the battery.
Does any specific device or manufacturer come to mind?
Tahnk you

RE: Proximity Sensor/Transmitter

Depending on the weather, TV systems are actually getting pretty good at discerning vehicles, but they require clear line of sight.  

Inductive loops are probably the norm, but their replacement frequency is on the order of a few years, since the pavement is compromised to put the loops in place.

You might also consider conventional sensors, which I've seen on the approaches to weigh stations.
http://www.wavetrix.com/about2e.html
http://smarteksys.com/?src=overture

http://www.pwssigns.com/documentbank/uploads/G-10CS%20%20Wireless%20Permanent%20traffic%20TD%203%2009.pdf
http://www.meas-spec.com/traffic-sensors.aspx

If you do a search for "traffic sensor," you'll see that the choices are quite plentiful.

TTFN

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RE: Proximity Sensor/Transmitter

Our town dropped all "loops" years ago.  They are VERY expensive to operate. They are so problem prone that when they install them they always install several of them. (Like five or more.)

This is so when the loops break due to pavement movement someone can come out and try one of the other loops and hopefully find one that is still intact.  That also incurs expensive service calls.

What is now favored is video cameras that only sense motion, they don't actually care about vision.  They are mounted on top of the street lights, and signal light beams, and pointed at the area of interest.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Proximity Sensor/Transmitter

Unfortunately, they only work with a clear line of sight.  Fog, rain, etc., pretty much fubars the sensor; which is why my city is still installing loops, even on new streets.  The other stuff is still quite expensive to install, as well.

TTFN

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RE: Proximity Sensor/Transmitter

(OP)
Thanks to everyone for your input.
Because of the issues raised here we were hoping that some manufacturer out there has adopted sensor technology from industrial applications to use in traffic.
I'll keep looking at industrial equipment that may be adapted since it seems that there have been significant advancements in these areas of control systems.
Walt
 

RE: Proximity Sensor/Transmitter

Look at Sick Sensor Intellegence, they make a host of laser and IR sensors suited for your application, but you need some in-depth analysis of your application by someone who can see what you are talking about and take note of the specific challenges.

For example they make a sensor / scanner called an LMS that can be used to pinpoint the location of an object within it's field of vision and provide information on the movement or progression of that object in the field. We have them being used right now on sports fields to track player positions and in racing to track vehicles. Ever watch a race and see the little icons that follow the car with the driver info and wonder how they do that? That is how.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln  
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