Does it matter which way a hall sensor faces?

Thread Starter

Cyrus Mingley

Joined Apr 18, 2020
92
Iny bldc motor, there are 3 hall sensors, does it matter which way they face? The circuit has been out and a few were facing the coils and some were facing the motor cylinder. Does it matter which way they face? I assume they need to face the cylinder to detect where it is.image.jpgimage.jpg
 

Thread Starter

Cyrus Mingley

Joined Apr 18, 2020
92
That is not a part number I can find. Here's a TI part: http://www.ti.com/lit/ds/symlink/drv5023-q1.pdf?HQS=TI-null-null-digikeymode-df-pf-null-wwe&ts=1590355212167
On one side you will be closer to the sensor. On the other side, further away. It may or may nor make a difference, but why change from what the manufacturer did?
The motor was opened at some point, and some of the sensors got squished a little, so I didn’t know how they were originally, or if it even mattered.
 

jpanhalt

Joined Jan 18, 2008
9,746
The point I tried to make was, "it depends." Yes, they will detect something from both faces. But most people use the designated face, In fact, I have never seen an application where that wasn't the case.

It's a little like lacing shoes, You can go bottom to top (the usual way) or top to bottom. Both ways work, but the performance will be different.
 

Reloadron

Joined Jan 15, 2015
5,508
The point I tried to make was, "it depends." Yes, they will detect something from both faces. But most people use the designated face, In fact, I have never seen an application where that wasn't the case.

It's a little like lacing shoes, You can go bottom to top (the usual way) or top to bottom. Both ways work, but the performance will be different.
You know I never gave that a thought till you just mentioned it. I mean my entire life it never crossed my mind shoe laces work both ways. While like you I never used them in such a manner I have worked with some hall sensors where the opposite side was sensitive to the opposite pole. I have some old discontinued 4 wire Allegro chips which go high on one wire for one pole and high on another wire for the other pole. I always liked them and can't figure out why they were discontinued.

Ron
 

dendad

Joined Feb 20, 2016
3,566
As I understand it, if you reverse the Hall sensor, the magnetic polarity needed to operate them will need to be reversed as well, so that will muck up the motor commutation.
If you can get an analog Hall sensor, hook it up and measure the output voltage. Then experiment with moving a magnet around it and see what that does.
The digital versions are just the same, but have a threshold sensing circuit driving the output switch.
 
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