I'm trying to work out whether the Arduino Due could drive an inductive coil with an since wave signal (for a small scale traffic sensor) to detect different materials, sizes and orientation, and then be able to read a change of inductance on that same coil when it is covered by something which changes the capacitance?
If not, would I need to drive the coil with external components (LCR circuit)? Or connect those components to be tunable by the Arduino and read the output with different pins?
I'm trying to work out whether the Arduino Due could drive an inductive coil with an since wave signal (for a small scale traffic sensor) to detect different materials, sizes and orientation, and then be able to read a change of inductance on that same coil when it is covered by something which changes the capacitance?
If not, would I need to drive the coil with external components (LCR circuit)? Or connect those components to be tunable by the Arduino and read the output with different pins?
Thanks in advance, D
Inductive sensors of this type would use the coil as the inductance in a tuned circuit. The coil is part of the circuit that determines the frequency. The receiver part senses the frequency and triggers on a change of F due to the inductance change producing a different frequency.
Simply feeding PWM into a coil from a fixed frequency would not work as the F will not change with inductance change. It may work if you can sense a drop in level due to the object absorbing some of the energy from the coil.
You would need a drive transistor to handle the current into the coil.
The differentiation of orientation, size and material will be somewhat more difficult.
Ahh, yes, I get you now. The coil IS the induction loop, why this wasn't intuitive to me I do not know.
Anyway, the plan is to build a small scale traffic light detection system based on an induction loop optimised to detect not only cars but also be able to detect bikes better.
So even though my plan is to drive the circuit from an Arduino, it does need the possibility to be scaled for industrical/commerical use, which will of course not be using an Arduino.
Can anyone answer me this though, whenever I see a traffic light induction loop on Google Image search there seem to be only one coil? So this implies to me that the circuit senses a change in induction rather than relying on a second detector circuit?
The single loop is part of the tuned circuit. A vehicle passing over the the loop changes the the inductance and hence the F. The detector part senses this change.
Hi,
With a single coil detector, you monitor the current in the coil, with constant drive frequency, a change in inductance will cause change in current.
You monitor this with a resistor and a diode detector to give you peak current/volts.
The shape of the coil will produce different response.
If you look at the marks in the road when they fit the coils, you will find most of the time there are more than one and usually they are square, not circular.
jremington:
You are planning to design and market an improved vehicle detector, but you have no idea how they work.
This is an university project, so i do have an idea how it could work, but how to implement it to work with an Arduino is something to think about. It is supposed to be optimized to better detect bicycles either by investigating different coil designs and parameters, such as material, size, shape,surrounding substrate and possibly it's angle as well as possibly having it interact with a second coil. There has to error detection and confident vehicle detection.
I'm just putting some ideas out there until I feel I know what the possibilities are, as opposed to asking how to do it.
With multiple coils you can distinguish bicycles, covering one coil only, from bigger vehicles. Else you risk to miss the small signal of a bicycle in the noise of one big loop.
DrDiettrich:
With multiple coils you can distinguish bicycles, covering one coil only, from bigger vehicles. Else you risk to miss the small signal of a bicycle in the noise of one big loop.
