Apropriate hall effect sensor for reg. of cars?

Hello all mighty forum.

I'm contemplating using the arduino to count passing cars. What specs would an appropriate hall effect sensor have? Can you even suggest one?

Thanks

Just how close are these cars? All HE sensors I've worked with have only been good for a few mm detection range, there may be better ones but if your cars are zooming along a freeway I think another approach is called for.

As to what I don't know, maybe bouncing a lazer of them, an inductive loop or something. If the cars are on a production line then maybe pressure sensors.

So, where are the cars, how fast, can you dig up the road?


Rob

What specs would an appropriate hall effect sensor have?

Sorry there is no way a hall effect sensor can detect a car.

Do you have access to the road - you could put an induction coil in it and measure the change in inductance as the cars drive over.

If not your best bet is to use an IR emitter and detector to measure any reflected light from the cars.

Hello good people.

Thank you for all your insights. Much appreciated.

What I'm wondering is, if the system described is "possible" with the arduino? I though it was using the Hall Effect, but I must be wrong. My current experimental setup registers passing (overhead) cars with a light detector and/or a proximity sensor. It's for a computer science project evaluating different methods for vehicle counting.

Magnetometers

A more recent technology, magnetometers, has been developed for the portable vehicle counting industry. The magnetometers developed for vehicle counting detect distortions in the Earths magnetic field as a vehicle passes over the magnetometer. The sensor element and the recording electronics are built as a single unit. This unit is typically mounted in the middle of the lane you want counted, as a result, most units are designed to be very low profile, flat plate-like structures that are nailed or bolted down to the pavement in the middle of the lane. By incorporating two sensors in the same unit with a reasonable spacing, speed, direction and vehicle length can be measured. Some magnetometers are permanent installations. These units are buried in the pavement in the middle of the lane. These self-contained units operate off of batteries for several years. Data is retrieved via radio transmissions (which requires a nearby receiver/data logger unit), or a buried communications cable exiting at a roadside enclosure. Relatively low power consumption.

The pros for this technology are: One count per vehicle, even in very slow or stopped traffic conditions. Portable units can be mounted in roadways that are awkward or impossible for the other technologies, such as on curves or in tunnels.

The cons for this technology are: Units are mounted in the middle of the road, so there is a safety issue during set-up and pull-up. Units are prone to damage and have to be replaced or repaired at a pretty high rate. Counting accuracy is not as good as other technologies, but it is nearly always better than 95%, which is sufficient for the vast majority of counting applications. Cannot classify vehicles by axle distribution.

Above quote from:
http://www.vehiclecounters.com/articles/read.php?id=1

Many years ago I used a radar doppler module available as a kit from Maplin here in the UK to do something similar. The nearest thing I can find now is here http://cgi.ebay.co.uk/Doppler-Radar-Wireless-Module-Microwave-Motion-Sensor-/190425974444?pt=UK_Gadgets&hash=item2c5645c6ac#ht_4118wt_907

It may be worth a closer look

I don't know what you mean by "possible"?

Can I buy a cheap sensor, easily attach it to an arduino and replicate the Magnometer method described in the quote in my previous post.

Or do you mean achieve an equivalent result (detecting a metallic object near the sensor)? Then the answer is probably: yes.

Any thoughts of an appropriate sensor?

You know the complete scope of your project, but all we know are some abstract questions out of context. We don't know what your CS project requirements are?

I'm trying to figure out what methods of vehicle detection I can easily (I know very little about electronics) implement using my arduino. I have implemented some methods, and am now wondering if I can do vehicle detection using some magnetic phenomenon.

I'm trying to figure out what methods of vehicle detection I can easily .... implement using my arduino

It is not the arduino that implements the method it is the design and construction of the sensor. The arduino simply monitors the signal.

I though it was using the Hall Effect, but I must be wrong.

Yes you are a magnetometer is not made with a hall effect sensor. It is made by a coil producing an excitation field and two (or more coils picking up the field)

Yes you are a magnetometer is not made with a hall effect sensor.

OK. Thanks for the insights.

This (Magnometer) appears to be a method I can not easily implement. Thanks for all the input. Much appreciated.

If you want to know more about them then look here:-