Hall Effect positive south pole negative north pole

Thread Starter

Juan Andrew Sasongko

Joined Dec 4, 2017
18
Hi all.

After reading a few articles about hall effect books, I'm still confused why the south pole produced positive voltage & north pole produce negative voltage here. Take example from this image



I'm doing exactly the same as this pic. moving closer and farther from the sensor. But when I put the south pole of magnet face to face with the front side of the sensor, it will generate positive charges in the sensor.
Anybody could explain? Since the articles I've read only said that south is positive, and north is negative.
 

ericgibbs

Joined Jan 29, 2010
9,299
Hi Juan,
Have you tried rotating the hall effect device around its axis by 180 degrees.? then repeating your test, what do you see.?
E
 

spinnaker

Joined Oct 29, 2009
7,837
Hi all.

After reading a few articles about hall effect books, I'm still confused why the south pole produced positive voltage & north pole produce negative voltage here. Take example from this image



I'm doing exactly the same as this pic. moving closer and farther from the sensor. But when I put the south pole of magnet face to face with the front side of the sensor, it will generate positive charges in the sensor.
Anybody could explain? Since the articles I've read only said that south is positive, and north is negative.

What does your schematic look like? What hall sensor are you using. You should have a pullp on the sense pin. It is been my experience that each side of the sensor will react to a different pole.
 

nsaspook

Joined Aug 27, 2009
6,700
Hi all.

After reading a few articles about hall effect books, I'm still confused why the south pole produced positive voltage & north pole produce negative voltage here. Take example from this image



I'm doing exactly the same as this pic. moving closer and farther from the sensor. But when I put the south pole of magnet face to face with the front side of the sensor, it will generate positive charges in the sensor.
Anybody could explain? Since the articles I've read only said that south is positive, and north is negative.
There's a engineering difference between the transverse voltage physics of Hall effect charge carrier flow separation due to magnetic flux and the implementation of a particular Hall effect 'electronic device' sensor's output (voltage, current, encoded signal) in response to that flux.

 

ebeowulf17

Joined Aug 12, 2014
3,024
Hi all.

After reading a few articles about hall effect books, I'm still confused why the south pole produced positive voltage & north pole produce negative voltage here. Take example from this image



I'm doing exactly the same as this pic. moving closer and farther from the sensor. But when I put the south pole of magnet face to face with the front side of the sensor, it will generate positive charges in the sensor.
Anybody could explain? Since the articles I've read only said that south is positive, and north is negative.
Which exact hall effect device are you using? Linear / proportional sensors will have totally different output configurations than the hall "switches" that people often discuss. As @spinnaker pointed out, some devices will need a pull up resistor on the output, although that depends on the model. Sensitivity to different polarities also varies by device as @MaxHeadRoom mentioned.

So, there isn't any general truth or universal answer. It just depends on the device. If it's response is suitable other than the polarity, reverse the sensor or reverse the magnet. If neither of those are options, you'd need to choose a sensor with a different configuration.
 

Thread Starter

Juan Andrew Sasongko

Joined Dec 4, 2017
18
Hi Juan,
Have you tried rotating the hall effect device around its axis by 180 degrees.? then repeating your test, what do you see.?
E
Sorry I don't quite understand with the terms 180 degrees. But I tried putting the front-face sensor (the branded face of package) with the south pole of neodymium (please see image below)

it generates positive output. The same happens when I put the south pole facing the back-side/top-side/bottom-side of sensor, it will generate positive output, which means that if the south pole of neodymium is facing the sensor, it will generate positive output voltage
 

ebeowulf17

Joined Aug 12, 2014
3,024
What supply voltage are you using to power it, and what is the signal output voltage when no magnet is present? If everything is working right, this should be half the supply voltage.

Once we've established the null voltage (voltage when no magnetic field is present,) are you saying that the output voltage always goes positive relative to the null voltage, regardless of which direction the magnet is coming from? Or are you just saying that the output voltage is always positive with respect to ground? If it's the former, something's not right, whether it's damaged parts, mislabeled parts, etc. If it's the latter, that's perfectly normal.
 

Thread Starter

Juan Andrew Sasongko

Joined Dec 4, 2017
18
What supply voltage are you using to power it, and what is the signal output voltage when no magnet is present? If everything is working right, this should be half the supply voltage.

Once we've established the null voltage (voltage when no magnetic field is present,) are you saying that the output voltage always goes positive relative to the null voltage, regardless of which direction the magnet is coming from? Or are you just saying that the output voltage is always positive with respect to ground? If it's the former, something's not right, whether it's damaged parts, mislabeled parts, etc. If it's the latter, that's perfectly normal.
I'm using battery. When no magnet eys half the supply voltage.
No, just like the first post. I want to know why the south pole generate positive voltage, while north pole generate negative voltage? It's written also in the datasheet of UGN3503UA that "if south magnetic pole presented to the branded face of the hall effect sensor will drive the output sensor higher than the null voltage, north pole will drive the output below the null".

I'd like to know how this happened.
 

ebeowulf17

Joined Aug 12, 2014
3,024
I'm using battery. When no magnet eys half the supply voltage.
No, just like the first post. I want to know why the south pole generate positive voltage, while north pole generate negative voltage? It's written also in the datasheet of UGN3503UA that "if south magnetic pole presented to the branded face of the hall effect sensor will drive the output sensor higher than the null voltage, north pole will drive the output below the null".

I'd like to know how this happened.
I misunderstood your question before. It sounds like the device is performing exactly as it is described in its datasheet - it's working perfectly. The only "problem" here is a perceived difference between the behavior of this Hall Effect IC compared to articles you've read about the Hall Effect.

@nsaspook already answered this point. The physics of the Hall Effect are well documented and it's a pretty safe bet that what you've read about it is true... but when you use any integrated circuit you're no longer seeing the effect in its raw form. You're seeing the net effect of all circuitry included in the IC, along with any effects due to the physical arrangement and construction of the IC.

So, it may be that the actual Hall device within the IC is oriented differently than you think it is, or it may be that the amplifier stages in the IC are inverting, making positive become negative and vice versa. As an end user, none of that matters. You don't get to work with each signal and sub-circuit within the IC, you only get to work with its output. Based on their chosen design parameters, the IC manufacturer decides how they want it to behave and documents it accordingly. As long as the device performance matches the datasheet claims, you're in good shape.
 
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