Hall sensor question

Dacflyer

1 W
Joined
Apr 20, 2022
Messages
59
Location
Fayetteville , NC
Ok, I been working on a hub motor for a while here.
Had to reglue the magnets in the core.
I centered them all evenly, all magnets are defiantly in right, and reassembled, everything seems to feel fine, nothing scrubbing.
I ohm'd all the field windings, All checks out ok..
So I connected the harnesses for power and the hall sensors. I turned the unit on, so far so good. No smoke.
next i gently budged the throttle, it jumped for a second, then nothing. Uh oh, what's wrong.
Nothing obvious. I double checked things, all looked good.. i touched the throttle again, nothing...holding it just a tad and using my foot to roll the rotor, the motor erratically jumps , bumps hit, buzzes in certain spots.
Hmmm, Maybe something with the hall sensors, because the controller needs then to know what phase to drive. Kinda like timing.
So i get testing equipment out to start testing. i made up a lil jig to watch the hall sensors sequence. if i slowly rotate it, in certain spots the leds will sequence. 1,2,3,1,2,3 then other spots nothing maybe a single blink..

My question is...aren't the sensors supposed to sense every magnet in the ring ?
since i reglued the magnets, Is it possible the sensors aren't able to sense every magnet? If so how can i fix it? Suggestions.
I think once the sensors detect every magnet reliably, then it'll work..
I know I'll probably have to take one of the covers off,
 
They should trigger in the same sequence for the entire rotation of the magnet ring. (rotor)

If they don't, the most likely thing given the repair performed is that either there is too big a gap (airgap) between some of the magnets and the halls (I think it would have to be a pretty big gap, so this is unlikely), or some of the magnets might not be installed in opposing polarity to the ones next to them (they should all alternate; you can test that with another magnet near them, it should be alternately attracted and repelled by each one it passes).


They are probably working fine, but you can also test the sensors by repeatedly moving a magnet past them manually (with teh motor open); most motor hall sensors are latching bipolar so their output will only change when the polarity of the field near them changes (not just when a field passes and goes away), so to trigger one you have to pass the magnet's N pole then it's S pole (or use two different ones opposingly oriented).
 
The magnets are defiantly in correctly, they let you know if they aren't by fighting you big time.. and yes, all of them are alternating polarity.. I ran a magnet around the ring before assembly.. N S N S N S
Dumb question, would the magnet ring orientation make a difference ? like the N S if they are N S N S and should be S N S N?
Could that cause issues ? Hope my explanation makes sense.. I think I'll have to take it apart and dig into it more, I think some of the halls are in a divot in the rotor and 1 is in between.. I'll take pictures this weekend. Getting that ring off the rotor is gonna be a bugger !
 
Dacflyer said:
So i get testing equipment out to start testing. i made up a lil jig to watch the hall sensors sequence. if i slowly rotate it, in certain spots the leds will sequence. 1,2,3,1,2,3 then other spots nothing maybe a single blink..

In your LED sequence, does the 1,2,3 mean... #1 led lit,#2 led lit, and then #3 led lit, individually in sequence? Or is it one led on, two leds on, and then 3 leds lit?

Did you have to move any of the sensors out of there position(s) while doing the magnet work?
 
when i rotated only 1 led seemed to be on at a time. sequential, I looked at some videos online and mine didn't seem to react the same way theirs did.. and mine acted erratically like as if each magnet wasn't triggering them.

No halls were moved during magnet work.. they were on the rotor with the copper windings.
the magnets were alone on Iron ring, centered as best as possible, all evenly spaced.
I'll take it back apart soon to see if i see anything obvious. I hope i can pull the ring free from the rotor..
 
Should follow the commutation table with a correct 120 degree hall spacing. 1 is hall on, zero is hall off in the table.
E475DB1F-0ED9-417C-A4D8-921083F0C058.png
If you’ve used the same magnets and they are curved then i guess you could set a N magnet upside down as S and affect the hall triggering by that, switching field will be distorted if some magnets are correctly placed and some not even if it’s N-S-N-S

But the old glue and the slight curve should be obvious..?
 
These magnets are flat. Also when i got this motor, there was no signs of glue if ever there was any..
I did discover something odd. I worked on the motor some, I checked internals and they seem put.
and just out of curiosity I touched the edge of the magnet with a small flat screwdriver, and there is virtually no magnetism on the edges of these things. I'm wondering if the magnets are not far over enough to one edge of the ring.. Am I over thinking here ?
My logic made sense to center the magnets.

I flipped the ring over and reassembled just to see if that made any difference. I retested, The halls seemed to change just a tiny bit.
but still very erratic. It is as if the halls aren't sensing the magnets very well..

What can i do at this point? I doubt I can do anything more with the magnets..
if i was able to find another motor i'd order one, But this one looks like a custom design and no leads..
 
Just check the table if they are correctly read.

One way of getting magnets unglued is to overheat them. They could be cooked and therefore lost strength. Was it ever working before? Pic of motor rotor and stator and detailed pic of hall placement would help.
 
No, these are all still stupid strong...Trust me..lol
There was no residue to be seen...now Previous owner may have cleaned off old glue.. I got this motor in a bucket.
I think I bought into a project that i shouldn't have..

I did read the table, there is no pattern to observe.. I made a small led jig to test the halls, I get maybe 1 spot where i have a pattern. like the table shows, the motor moves like a stepper motor, it has well over a few hundred steps, if i call that right?
the motor can move in fractions of a degree ,I think i counted 32 magnets and 36 poles. i don't know what useful info this would be ..
 
Ok, then hall switching is NOK. Root cause could be several but as you got it in a bucket it might be the halls in the wrong positions. picture will help us help you.

32 magnets is 32 poles if the magnets are not placed in pairs or triples to form larger poles (as nnn-sss-nnn) so i assume you have 36 slots and 32 poles?

Hall spacing can be either 120 degrees geometrical or 120 degrees electrical where electrical degrees is geometric degrees divided by number of pole pairs, 16 pole pairs is assumed for this motor based on your info.

If the halls are in the slots:
Halls should be either evenly spaced in slots 1,13 and 25 or 120/16+n*360/16 degrees apart where n is any number from 0 to 5.

The positions closest in the slots with correct spacing will then be when the hall spacing can be evenly divided by the slot spacing
slots are 10 degrees apart, 360 degrees electrical is 360/16=22.5 degrees geometrical so n=1 will be in a slot and halls can be in slot 1,4,7 and have the correct distance.

If the halls are on a pcb then more freedom is possible, sensors can be positioned at the closest (and correct) distance apart since they are not bound by the slot spacing. Then distance is likely 7.5 or 30 geometrical degrees apart.

Edit: i just saw that you had some issues getting the magnets glued in the right place. That could also affect hall switching, if magnets/poles are not symmetrically located. Did you get all new magnets or only a few?

How do you know what magnet number it was in the first place?
 
ok,, I'm going to copy you here and answer each question,,,

32 magnets is 32 poles if the magnets are not placed in pairs or triples to form larger poles (as nnn-sss-nnn) so i assume you have 36 slots and 32 poles?
I don't understand ( slots ) Is that the spaces between the poles ? When i say poles, I'm referring to the number of windings on the stater. ( sections? )

Hall spacing can be either 120 degrees geometrical or 120 degrees electrical where electrical degrees is geometric degrees divided by number of pole pairs, 16 pole pairs is assumed for this motor based on your info.
The hall sensors are embedded in the poles of the stater. left and right are in a cavity in the pole, and the middle one is in between the poles. I can supply pictures in the next post, I'm on my laptop here and need to use tablet to make the pictures. Also the halls are on a small circuit board.

If the halls are in the slots:
Halls should be either evenly spaced in slots 1,13 and 25 or 120/16+n*360/16 degrees apart where n is any number from 0 to 5.
The halls are all grouped at 1 side of the motor, all closely spaced together..they are not spread around at 120 degrees.

The positions closest in the slots with correct spacing will then be when the hall spacing can be evenly divided by the slot spacing
slots are 10 degrees apart, 360 degrees electrical is 360/16=22.5 degrees geometrical so n=1 will be in a slot and halls can be in slot 1,4,7 and have the correct distance.

If the halls are on a pcb then more freedom is possible, sensors can be positioned at the closest (and correct) distance apart since they are not bound by the slot spacing. Then distance is likely 7.5 or 30 geometrical degrees apart.

Edit: i just saw that you had some issues getting the magnets glued in the right place. That could also affect hall switching, if magnets/poles are not symmetrically located. Did you get all new magnets or only a few?
When i got the motor, the magnets were in the ring core..there was what appeared to be 1 missing, and 2 broken ones. So after a few post on here and some more searching on my own, I found a place here in the states, and they magnets i needed was a stock size. So I ordered 3 of them, I removed the 2 broken ones, and tried to ass the 3rd one,,Wouldn't quite fit,,,was just a fraction off.
So now what..Maybe i need some spacers? so i used card paper to put between every magnet to close the gap perfectly. and i didn't need the 3rd magnet. I thought i knew what i was doing...Maybe not ? Is there a rule of thumb on how many magnets to poles on the stater there should be?? Maybe i have too many magnets in there ?? I hope this helps you, I'll add some pictures in a while here..


How do you know what magnet number it was in the first place?
I didn't, I just went with what i saw. I don't know if the PO added some more in there or not. I'm assuming he tried to repair it and then gave up..
 
Is there a rule of thumb on how many magnets to poles on the stater there should be??
Yes, only some combinations work well.

Poles= magnetic poles, almost always same as number of magnets.
Slots=number of teeth on the stator
If the halls are fitted into the stator steel then take a pic of them so the spacing can be estimated.
 
Each hall sensor should toggle on/off as each magnet gap passes by. The chart larsb posted shows how the hall signals should look as the motor is turned. You can check each hall signal to be sure they are all toggling on/off at each magnet interface. In some positions, there should be two halls high, one low. There should be no positions where all halls are off or all on.

The number of magnets will always be even. North, south, north, south, etc...
The number of stator poles will always be a multiple of 3 for a 3 phase motor.
 
Have you verified the hall sensors erratic and intermittent operation individually with a multimeter?

If so, what is the supply voltage for the sensor's operation?
And what are the Hi/low voltages for each signal wire?
 
Ok,, here is the pictures i said I'd post...
Also i need to correct myself., i don't know what what i was thinking earlier.
It's actually 32 magnets, and 36 poles

20220611_164550.jpg
20220611_165347.jpg20220611_164421.jpg20220611_164344.jpg20220611_164321.jpg20220611_164313.jpg20220611_164211.jpg20220611_163858.jpg20220611_163851.jpg20220611_165618.jpg20220611_165604.jpg
 
Tommycat >>> Yes, as i stated earlier, i made a 3 phase led tester for the halls.. Some spots detect, others don't, i think there's maybe 1 spot that will mimic the chart posted earlier.. From what I seen in other videos, the leds usually sequence in 2's,, mine does none of that.. 1 maybe 2 leds, all random, no sequence to them, but all 3 leds do detect, just not properly.. Most areas not at all.. The halls are supplied 5vdc..
 
It looks like the magnets are too short. What width were the originals?

In the motors I've opened up, the magnets are usually about the same length as the width of the stator lamination stack. AFAIK, if they're not, it's "wasting" some of the torque it could have had, as there is not enough magnet for the rest of the field to push against from the stator.

In this case, perhaps it may also cause the halls to not respond reliably if the magnet field doesn't go thru them correctly as they pass the halls. If some magnets are slightly more over the halls than others, then it would explain why you get a response at some points during a rotation of the rotor, and not at others?
 
I have no idea what to do at this point..
I'm willing to send this off to be fixed if there is some place that can do it..
Or if another could be bought.. I feel as if i have hit a dead end here..

These are the magnets that came with it..I know nothing more..
The magnets I bought were about $5 ea + tax and shipping.
I could try and see if they have something a tad wider. But then i don't know if the end caps would fit on..because they go on the inside of the ring to center the stater..
I can contact the company I bought the magnets from and see what is available..But what you say, Kinda makes sense..
 
The magnets have to pass over the center of the hall sensor. If the magnets are shorter so they don't go over the sensors, that could be a problem.

Looks like a pretty hefty motor.
 
Dacflyer said:
.
I could try and see if they have something a tad wider. But then i don't know if the end caps would fit on..because they go on the inside of the ring to center the stater..
some pics of other motors to show cover lip clearances vs stator/magnet width

file.php

viewtopic.php

motorino_motor_jbweld1.jpg

motorino_motor_new_wires.jpg

motorino_motor_varnish1.jpg

https://endless-sphere.com/forums/viewtopic.php?f=3&t=66489#p1002581
leafmotor_10.jpg

leafmotor_09.jpg
 
Dacflyer said:
I have no idea what to do at this point..
I'm willing to send this off to be fixed if there is some place that can do it..
Or if another could be bought.. I feel as if i have hit a dead end here..
Looks like the winding is toasted, this is probably the cause to both magnets coming loose and that it doesn’t work.
641F0B2F-A3B2-4A59-9D77-EB3B04DF6A8C.jpeg
It means that motor has been hot enough to char the windings and there is definitely a risk that the magnets have been cooked enough to lose the original strength. I’m sad to say it but if you’d posted those pictures from the start then you’d avoided a lot of work as this motor will probably need a rewind and a replacement of all magnets and possibly the hall sensors too, they also get damaged in heat.

Now what to do? Leave it and go take a cold brew with a friend
29DBCF16-9656-43F8-97AA-1ABEF068187C.gif
Then decide if you want to continue with this motor. :wink:
 
what's toasted about it? i cant see a problem?


larsb said:
Dacflyer said:
I have no idea what to do at this point..
I'm willing to send this off to be fixed if there is some place that can do it..
Or if another could be bought.. I feel as if i have hit a dead end here..

Looks like the winding is toasted, this is probably the cause to both magnets coming loose and that it doesn’t work at all.
641F0B2F-A3B2-4A59-9D77-EB3B04DF6A8C.jpeg
Sad to say it but if you’d posted those pictures from the start then you’d avoided a lot of work, this motor will probably need a rewind.
 
No, don' think so, it's crumbly looking too. I had one of my motors smoking hot and it didn't look like this afterwards. But dacflyer can check it in real life :thumb:

It should have that smell of burnt plastics too if it's cooked.
 
Back
Top