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Metal detection by hall effect sensors

Former Member

Hi,

 

I want to build a metal detector through a Hall Effect sensor. This detector will be a rectangular tube design hollow from inside and multiple Hall Effect sensors will be arranged along the length of the tube in the inner walls. Now when a metal object passes through the tube, these sensors should be able to tell about it. The whole idea is to utilize the variations in the earth's magnetic field inside the tube when metal object passes through and sensors will pick up this little variation to detect metal. Since there will be multiple sensors, so they will report the findings to an Arduino which will do sensor fusion and make the decision about detection.

 

Now, I know this could be difficult with Hall Effect sensor. The variation in the earth's magnetic field will be too little for the sensor to detect it. However, there could be some way of getting this done. One way could be to magnetize the path inside the rectangular tube, so a passing by metal object gets magnetized and induce greater variations in the field.

 

Could you recommend some other possibilities of doing this. Some solution, that will give very reliable detection, zero false alarm and better range of detection so that the size of rectangular tube could be actually increased, making this design practical?

 

I would look forward to the suggestions of you guys. Kindly reply

 

Thanks

  • Hi Umair,

    Do you know ahead of time what type of metal will be passing through the tube? Are you going to want to discriminate different materials or metals? How fast are the materials moving through the tube and what is the resolution that you are looking for ( how close can the materials be before the sensor calls it one item)? What is the composition of the tube? Why Hall Effect sensor if the material is not inherently magnetic?  As you can see more information is needed on your project and its purpose before our responses will have any value.

    John

  • in reply to jw0752

    Hi John,

    Thanks for the reply.

    Basically, I am developing this project as part of my Masters degree. The main consideration is to design it without the coils so that it comes up as a new concept.

    Now, to prototype this detector, I can start with Ferrous metals, so say yes I do know ahead of time about the type of metal. Later on I will experiment with non-ferrous metals.

    Differentiating between materials depend upon the response i get from the sensor in terms of specific signatures corresponding to different metals, I dont consider it for time being, could be a part of extension later.

    Metals could lie apart from each other at min 3 or 4 inches in a straight line.

    The design of tube depends upon the configuration of sensors inside it. It could be rectangular or circular. I will try with a wooden tube.

    I tried various magnetometers and their response and ranges were quite weak, so I am now looking to do it with Hall Effect ratiometric sensor, as it gives constant voltage output proportional to magnetic flux density. I have read many tutorials and videos, people doing a lot of stuff with these, so I picked this idea from there.

     

    So, thats the deal so far. Hope you get a better and complete picture now.

    Best Regards John

  • in reply to Former Member

    I see you have entered your question twice and you are getting responses in two threads. Based on what you have explained I like what Don told you about using a Hall Effect sensor with an artificial magnetic field across the tube. Then when the metal comes down the tube the Hall Effect Sensor will detect the change in the artificial field. I will not reply on this thread again as it is two confusing to be getting responses from two directions. I will follow the other thread so if you want to respond to me I will see it over there.

    John