inductive loops for traffic management

[thuvu]

Hi everyone,
I am working on a project fot traffic control management. I want to be able to identify vehicles by their electromagnetic signature. When a car passes over a inductive loop creates a unique waveform. If it passes again I want to compare the waveforms to see if it is the same model.

I have the following info:
The circuit is a LC resonant circuit (LC) with input AC signal (10k-200kHz).
The car changes L and so the resonant frequency Fr.

I have to read the changes in Fr in order to create the waveform.

Does anyone know a circuit like this?

ps. My project will also have a microcontroller for signal processing.

 

[siongboon]

You can try looking for metal detector circuit.
These vehicle loop detector is a metal detector.
You can modified the circuit to provide you the
analog signal output you need for your
digital signal processing.

I like your project.
Sounds very interesting.


www.siongboon.com

 

[pixel]

Frequency measurement is not so big problem with microcontrollers. You should build look-up table from previous measuremant and than just to check similarity to measured data. I am not sure how much this method will give good results. Maybe you should use some dsp techniques like crosscorelation.

 

[thuvu]

Thank you for your replies but I have a problem with the analog part of the project. Does anyone have a schematic for such a circuit?

 

[temtu]

If you are interested in a "pure" analog solution, the best is Sarasota 215. Please check US patent 3683351.