Author Topic: Hall sensor to detect metallic objects.  (Read 708 times)

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Offline luiHSTopic starter

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Hall sensor to detect metallic objects.
« on: December 14, 2019, 12:26:01 am »
 
Hello.

I have a project in which I need to detect metallic objects (not magnetized). The distance from the sensor to the object will be about 5mm.

I am thinking of several systems, one would be using magnetic sensors from the Chinese, like those in the attached photo, another would be to build my own magnetic sensor, something similar to a metal detector with the PCB printed coil.

On the other hand, since I have to use hall sensors for other designs, in which I use neodymium magnets, it occurred to me if I could also use hall sensors to detect metallic objects. For example, by placing a small neodymium magnet between the hall sensor and the object to be detected, or the magnet near the sensor, so that by passing the metal object it alters the magnetic field of the magnet and is detected by the hall sensor.

I would prefer to use hall sensors, because it is simpler and cheaper than use magnetic sensors. I have seen some hall sensors that deliver an analog output that varies the voltage depending on the intensity of the detected magnetic field, these could help me.

Has anyone tried the use of hall sensors to detect non-magnetized metal objects?

Regards.
« Last Edit: December 14, 2019, 12:27:56 am by luiHS »
 

Offline Jannehrl

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Re: Hall sensor to detect metallic objects.
« Reply #1 on: December 20, 2019, 08:21:45 am »
You can do that.
For encoder measurements with magnetic sensors you can either use a magnetic tape or also a metal geartooth.
For the measurement with geartooth TMR Sensors are used.
In the picture below you can see how they are usualyy set up with a permanent magnet behind them.
In your case you wouldnt want to measure the the height difference of the metal, but if there is any metal at all. 
Also the distance of 5mm is well achievable, i think even up to 1cm you could reliably detect your object.
Be aware that you have to search for a TMR sensor, as GMR, AMR or others wont give you the same result.
Also dont forget that if you are using a pure TMR Sensor they mostly dont have a magnet already placed behind them.
Also Neodynium magnets are rarely used in magnetic encoding, im pretty shure because the field is too strong.
Try to use a normal ferrite first.
 


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