Adding hall sensors to outrunners

[Burtie]

The large HXT style outrunners seem to have some problems with currently available sensorless controllers :? :

1) They destroy sensorless controllers regularly .
2) They often have syncing problems when the throttle demand rises too quickly .
3) They suffer from unpredictable startup and poor slow running.

I am rapidly forming the opinion that robust sensored controllers are currently the best things to use with these motors.


There are two basic ways of fitting the required hall sensors to these outrunners -Internal or External.
Both methods have been tried and proven by a few brave members here (and I am very thankful to them).


Edit:

Update- When using the Turnigy 80-100 motors beyond about 3kw, the Internal hall sensors seem to give better results .
Probable explanation is that, at high power settings, the stator fields are interfering with the externally placed sensors.
http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=20588&start=585#p382018

...and not just my experience...

toolman2 wrote:
ive got some halls mounted up inside the big turnigy "130 kv" motor, and its now running well.
no luck as yet with them outside -allways noisy or maby interference from the coils magnetic field, hopefully the photos come up to show it.

Thud wrote:
For some stupid reason I had my brain totaly stuck in that "external" hall sensors would work for these big motors.
If burtie had politly said: Thud, you stupid tit! Put halls inside your motor & report back soon! We would have been untouchable in Tuscon. (at least thats what i say .LOL)

End update




Internal: You can glue them into the stator slots.
Relatively easy but not adjustable. Here is a link to my experience so-far with this method.
http://endless-sphere.com/forums/viewtopic.php?f=28&t=12768&start=60#p225084


External: You can position them around the outside of the can.
More work, but it means you can fine-tune the timing to get the desired results.
Here is what I did:






OH -NO!!!

http://www.youtube.com/watch?v=XVX5T7JkBDA
[youtube]XVX5T7JkBDA[/youtube]


Burtie

 

[AussieJester]

YOU IS da Man Burtie !!! I like the external method also...the internal is
also very good In your opinion which is the better method though? I'm
guessing the external seeing you now using this over the internally
mounted Halls...OH...is the Turnigy spinning at max RPM in that video?
Sounds like its a lil slower than full speed too me? I do like the start up
and idle speeds too, the 'revving' of the throttle results in crisp motor
response also...As always excleent job and documentation THANKYOU for sharing Burtie...

I guess your ball deep in snow now over in the motherland so your riding time is
non existent? Bring on Spring

KiM

 

[gwhy!]

Hi Burtie,
That is so much nicer and more compact with that spacing, I used 60degrees between halls so the mount was a little more work to make. Dont know why I didn't think of that, so is this 30degree spacing with the halls all facing the same way ?

AJ, you really need to get some halls on your motor believe me the E-grin just gets bigger and bigger... :wink:

 

[AussieJester]

?

AJ, you really need to get some halls on your motor believe me the E-grin just gets bigger and bigger... :wink:

If Recumpence (and others) can make RC ESC work i'll make do also at least until theres a sensored
speed controller thats not the size of a house brick...

KiM

 

[Burtie]

Hi Burtie,
That is so much nicer and more compact with that spacing, I used 60degrees between halls so the mount was a little more work to make. Dont know why I didn't think of that, so is this 30degree spacing with the halls all facing the same way ?

To achieve 120 degree electrical spacing, the mechanical spacing between each sensor for a 14 pole motor is 17.14 degrees. So the total arc is 34.3 degrees (I think :| ). All sensors face the same way.

I did some testing by waving a hall sensor around on the end of a bit of wire attached to a 'scope. The sweet spot for the cleanest signal was at about a 46mm radius (+/- 2mm). From here we just need to do a bit of trig to work out where to drill the holes in the plastic chopping board .

KiM,
The external sensor setup can be tuned to run with a slightly lower no-load current than the internal setup (3 amps as opposed to 3.6 amps). So looks like it may prove to be more efficient. Acid test is when I try it on the bike tho. So I will reserve judgement. Just waiting for them transistors from Mexico........


EDIT - 24volts in video, so only half speed.... Hang on.... Crazyman controller..... ....... means I am not limited to 44v any more!! WaaaaaaayHaaaaaaaay!!!

Burtie

 

[liveforphysics]

HoORAY! for Burtie!!! Great work!

I like your setup much better than mine.

I bet some of the problems with my setup being so sensitive to any tiny change in hall sensor position came from the sensors being snugged up as close as I could get them to the magnets.

 

[liveforphysics]

You're going to like the power of that motor SOOOO much more when you're running on 100v. For my bike, my first test run on 100v was done when I only had 1 motor setup for 100v, and the other motor was just getting dragged along. It performed as well or better with just a single motor on 100v than it did with dual motors on RC controllers at 48v.

 

[Burtie]

Luke,

That twin motor bike is totally Mad-Max.
How fast does it go on 100volts?

I found that the halls would give unwanted extra pulses when placed too close to the magnets, even when the stator was not energised.
I wonder if they were seeing the flux leaking around the edge of the magnet (which would be in the opposite direction).

Burtie

 

[liveforphysics]

Luke,

That twin motor bike is totally Mad-Max.
How fast does it go on 100volts?

I found that the halls would give unwanted extra pulses when placed too close to the magnets, even when the stator was not energised.
I wonder if they were seeing the flux leaking around the edge of the magnet (which would be in the opposite direction).

Burtie

I don't have a clue what it was seeing to be honest Burtie. Mounted them at the spacing Jeremy Harris used, and tried to get them as close as possible to make sure the flux would switch them. The end result was that my sensors were extremely sensative to position, temp, etc. It was a huge improvement over RC controllers due to the durability, and 100v ability, but it never worked as well as I wanted due to the sensors always seeming to need to be tweaked.

As far as speed on 100v, it's 64mph, and gearing limited not power limited.

 

[gwhy!]

?

AJ, you really need to get some halls on your motor believe me the E-grin just gets bigger and bigger... :wink:

If Recumpence (and others) can make RC ESC work i'll make do also at least until theres a sensored
speed controller thats not the size of a house brick...

KiM

Hi Kim, Im not sure why you think you need a controller the size of a house brick :? , the little 6 fet controllers are not really any bigger than the CC rc controller cos you need to add a BEC and throttle interface so it comes out the same size and my little 6 fet can push 5kw no problems on 44v and in theory i can up that voltage upto 70v which would be 8kw +.

 

[Thud]

Burtie,

Thanks for posting this. very nice & clean. (love the Astro rotor option also)
(I have rc controllers, but never had confidence in them in this application)
Burtie said:

To achieve 120 degree electrical spacing,

Can you (or anyone please) give quick explanation of the math to arive at the 34.3 deg? or a link to clarify the correction factor from mechanical geometry to electrical?
I was under the asumption that true angular array would be "the" ideal spacing. (amature motor builder here-this is valuable info)

looks like I will be modding controllers to 100v sooner than I thought LOL.
Thanks again. T

 

[Tiberius]

Good work Burtie,

I think I'm going to try that myself. What Halls did you use?
It looks like it should be possible to design a PCB that would bolt to the back of the motor and hold them in the right position. I have the serious PCB layout software if that looks like a possibility.

Nick

 

[Jeremy Harris]

I've now fitted Halls to three motors, including one that I rewound with thicker wire. I chose to fit the Halls inside, in the slots, because is is pretty simple and leaves the outside of the motor looking like a stock motor, with just an extra five wires coming out of it.

The sensors I used were Honeywell SS411A latching sensors, http://sensing.honeywell.com/index.cfm?ci_id=140301&la_id=1&pr_id=149893

All that's been said here rings true with my experience so far, although I've not pushed motors at the sort of power that others have. The most significant difference between running sensorless and running with Halls is the low speed torque and start performance. I'm still amazed at the way a motor fitted with Halls will just tick over very slowly, but with enormous torque.

Some sort of robust, universal, Hall mount kit would be great. Virtually all these big RC outrunners are 12 slot, 14 magnets, they only vary in terms of diameter. There may just be room to fit a thin, curved, PCB inside the motor, between the stator and the base plate. Certainly having the sensors inside has the advantage of being a bit more robust.

Jeremy

 

[Burtie]

Burtie,
Can you (or anyone please) give quick explanation of the math to arive at the 34.3 deg?

Hi Thud,

I justified it to myself like this:

Given that we accept 120 mechanical degree spacing works for a 3 phase motor like this one.
The can has 14 evenly spaced magnets around it.
So for one revolution, the magnetic pattern repeats 7 times.
We could put a hall sensor in any one of 7 positions and it would give the same signal.

The spacing of those positions is 360/7 = 51.42 degrees, (for one electrical revolution).
But we need 3 equally spaced sensors for one electrical revolution: 51.42/3 = 17.14 degrees between the sensors (I think :? .)

Burtie

 

[Thud]

Hmnnn.
Your explanation makes sence, but It is a different view point.
You don't sound so certain yourself

But we need 3 equally spaced sensors, 51.42/3 = 17.14 degrees between the sensors (I think .)

I don't know enough to make it a debate, My thoughts were based upon the stator teeth & 3 phase power.
logicly, the magnet poles are the hall trigger for the coil charging sequence, but they are angularly varient by quantity.

I thought the charge angles in the stator (60 degrees) would determine the correct spacing of the triggers. The magnetic pattern of the poles are a repeating pattern.

you may have a formula though that does the exact same thing

If you have time to test the performance of a true 30- 60 or 120 vs the 34.3 I would really like to know.
Wheres Fechter when you need him?
Thanks for the info. T

 

[kfong]

Great job Bertie, I wonder if that angle difference is the reason you are drawing less current at no-load or are both the internal fet and external fet the same angle?

 

[bigmoose]

Guys I think I will have some data to offer that might help when I can get a little time to create the external flux maps for a quadrant of the large Turnigy outrunner. A really good friend of mine got me one for my birthday! So now I have no excuse to not get busy and work on sensoring it. Below is a little picture of me with my Bell 9640 Gaussmeter. First off, the Turnigy leaks flux out the backshell, we know that because the paperclip sticks. But now we know the magnitude, around 900 Gauss maximum. But the flux leakage end effects make for a very, very interesting pattern... it looks like they even reverse polarity when running in the same radial position but scanning axially from bell to bell. I haven't tried measuring the effects of an energized coil does to the backshell residual flux. That will need to be done also after the static case. Preliminary results says that folks are placing the sensors in a non optimum position, too close to the static bell.

If you want a measurement in a specific spot, let me know and I'll try to knock it out first for you before I do the labor of the mapping.

Bear with me, I don't work on as fast as you guys do on the non client work.

 

[kfong]

That would be great Dave. Once you have the optimal position determined. I can CNC a fet mounted bracket to verify it. I bought one of those Turnigy motors as an RC setup for my third e-bike. I'm hoping it will outperform my previous and current ebike I'm building.

 

[Thud]

I will trust a gaussmeter over my "guessmeter" any day.
Thanks for pitching in Dave.
If you can tell me where the Optimum spot is I will subordinate to that.
Given the leakadge you have found initialy, are there gains to be had with an improved flux ring?

maybe you will shed some insight as to why this motor is such a controller buster.
(these eat standard rc controllers with regularity also it seems)

 

[swbluto]

The wealth of knowledge, experience and equipment on this forum amazes me.

 

[liveforphysics]

Guys I think I will have some data to offer that might help when I can get a little time to create the external flux maps for a quadrant of the large Turnigy outrunner. A really good friend of mine got me one for my birthday! So now I have no excuse to not get busy and work on sensoring it. Below is a little picture of me with my Bell 9640 Gaussmeter. First off, the Turnigy leaks flux out the backshell, we know that because the paperclip sticks. But now we know the magnitude, around 900 Gauss maximum. But the flux leakage end effects make for a very, very interesting pattern... it looks like they even reverse polarity when running in the same radial position but scanning axially from bell to bell. I haven't tried measuring the effects of an energized coil does to the backshell residual flux. That will need to be done also after the static case. Preliminary results says that folks are placing the sensors in a non optimum position, too close to the static bell.

If you want a measurement in a specific spot, let me know and I'll try to knock it out first for you before I do the labor of the mapping.

Bear with me, I don't work on as fast as you guys do on the non client work.

Whoa!!! It's so so cool to see a legend holding the big Turnigy motor. This can only bring good things for us. I'm not a fortune teller, but I've got a prediction we're going to see some very good things happen for the RC motor crowd. There's so much brain power looking at that motor, it's probably shaking with fear in his hand while wondering what crazy ways he will think of to milk the maximum power from it. lol These are good times for the RC motor builders. The RC controller limitations are soon going to be a memory from the past.

 

[Burtie]

Dave,
Great to have you involved, and that fluxmeter looks like a useful piece of equipment

Thud wrote:
If you have time to test the performance of a true 30- 60 or 120 vs the 34.3 I would really like to know

Thud,
I have internal 120 degree sensors and external 17.14 degree sensors fitted to the same motor, so the performance comparison should be easily done once I have it fitted back on the bike.


I used the same type of latching sensors as Jeremy did, the Honeywell SS411A .

Burtie.

 

[AussieJester]

I will trust a gaussmeter over my "guessmeter" any day.

Shouldnt that be your "Guessomometer" Thud

KiM

 

[gwhy!]

Hmnnn.
Your explanation makes sence, but It is a different view point.
You don't sound so certain yourself

But we need 3 equally spaced sensors, 51.42/3 = 17.14 degrees between the sensors (I think .)

I don't know enough to make it a debate, My thoughts were based upon the stator teeth & 3 phase power.
logicly, the magnet poles are the hall trigger for the coil charging sequence, but they are angularly varient by quantity.

I thought the charge angles in the stator (60 degrees) would determine the correct spacing of the triggers. The magnetic pattern of the poles are a repeating pattern.

you may have a formula though that does the exact same thing

If you have time to test the performance of a true 30- 60 or 120 vs the 34.3 I would really like to know.
Wheres Fechter when you need him?
Thanks for the info. T

Hi Thud,
I think it gets a bit confusing because we are mimicking 120degree spacing for the sake of the controller, I myself am using 60degree mechanical spacing but this in itself is slightly out when viewed on a scope ( I never bothered looking into the slight miss placement/timing because it worked well ) But now I have looked into since the start of this topic it makes sense. If you use true 30 or 60 degree mec spacing ( the controller would have to support these spacings )the switching points become shifted ( a lot more noticeable with 30 degree spacing ) so the switching points need to be re-adjusted hence 34.3 degrees mech.

edit:

Bertie the 17.14 degrees will be equivalent to 15degree spacing I think.. is it not. if it it was 30dergee spacing one of the halls will have to be flipped i think :?

 

[Thud]

gwhy,
Thanks, that makes it even more understandable. I tend to get cought in the straight mechanicle analisys of things.
I have my 1st e-crazyman controller on the way & have plans to run my big turnigy with it. With the info on this forum I should be able to exceed all expectations.

Burtie, this thread came at the perfect time for me as I am just starting to figure the hall placment in my axial motor build.
thanks again.

Gauss-0-mometer......I like it LOL.