Adding hall sensors to outrunners

[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.

[gwhy!]

From what I have been playing with it looks like the 15 degree spacing is the best way to go ( no flipping hall sensors/signals ) using mechanical 15 degrees its far less disruptive to where the switching points are than what I am using ( 60 degrees mech ). The only thing I would say is as long as the leading edge of the first mag to the leading edge of the next is greater than 15 degrees then all should be well as long as the flux leakage isn't to great to cause false triggering.

[bigmoose]

I took a bit of the morning to run the flux leakage tests. The first pix shows the Turnigy C80100-130 in it's high tech wooden test fixture. The wires come out what I call the fixed bell. Station zero is the end of the outrunner closest to the fixed bell. The stations move towards the "prop end" in 0.25 inch increments.

For the first graph I aligned the center line (C/L) of one magnet with a pole. I measured down the center line of the magnet on the exterior outrunner shell. I then measured down the line marked 10 degress CCW looking into the motor from the prop end, 20 degress CCW, and finally 25 degrees Counter ClockWise.

For the second graph I turned the fixed bell 10 degrees CCW, and repeated the three measurements above.

For the third graph I turned the fixed bell 20 degrees CCW, and repeated the three measurements above.

My Preliminary Conclusions... don't you love engineers that work in "high risk" areas? Everything is "preliminary", until the project is successful.

From the first graph you can see that things are funky near the fixed bell. You have to get at least to station 5, or 1 inch from the fixed bell to get a decent signal. (Yes, Excel added a 1 to my station numbers. Excel station number 1 = Turnigy Picture station 0. You also need to stay clear of the prop end, but not by so much, s minimum of two stations or 1/2 inch.

If it were me, I would put the hall sensors over station 7, or 1.5 inches from the fixed bell towards the prop end. That looks to me like the preliminary optimum at this time.

I could just sneak my probe into the assembled motor to measure the surface flux on the magnets when they were between pole pieces, I measured right around 4900 Gauss. I could almost jam the probe into the air gap between the magnets and the pole piece, but I couldn't justify the cost if I ruined the probe, so I didn't do it!

I'll cut the plots a bit different and post them in a while.

[bigmoose]

Here is the same data plotted a little differently. Each plot is for a particular scan relative to the magnet center line, and then it has curves for the stator aligned with the magnet center line, advanced 10 degrees CCW and advanced 20 degrees CCW. There is a total of 4 graphs that correlate with the curves that were on the previous.

[liveforphysics]

*Luke runs over to his crappy hall sensor brackets and starts traceing a template out to make a spacer and raise them to the #7 middle position on the rotor bell. *

[bigmoose]

Luke, there is always a twist and turn in the road. I went back and looked at your twin Turnigy bike build thread, and it looks like I have the new Generation 2 Turnigy C80100-130; and your build might have used the first Generation. My silver outrunner bell looks longer than yours and is 3.130 in. ish from memory. Also mine has a big, like 2 inch ish bearing on the stator bell, I also have the screws on each end. (ish is a technical term that means I'm too tired to go back downstairs and remeasure it... so I go from memory!)

That said, I may have much more dead space in my version of the C80100 near the fixed bell than you do.

Looking at my flux chart it implies my magnets are around 1.5 inches long. Do you know how long yours are?

Always a twist, isn't there?

[liveforphysics]

Luke, there is always a twist and turn in the road. I went back and looked at your twin Turnigy bike build thread, and it looks like I have the new Generation 2 Turnigy C80100-130; and your build might have used the first Generation. My silver outrunner bell looks longer than yours and is 3.130 in. ish from memory. Also mine has a big, like 2 inch ish bearing on the stator bell, I also have the screws on each end. (ish is a technical term that means I'm too tired to go back downstairs and remeasure it... so I go from memory!)

That said, I may have much more dead space in my version of the C80100 near the fixed bell than you do.

Looking at my flux chart it implies my magnets are around 1.5 inches long. Do you know how long yours are?

Always a twist, isn't there?

You're right that my motors are the old-style with no lower skirt bearing like the fancy new style you've got. We both have identical sized stators though, so I would ass-u-me our magnets were also roughly the same length, and that your magnets just sit up a bit higher than mine to make room for the skirt bearing. This might mean my halls are ok where they are at height-wise.

[bigmoose]

We could use the symmetry of the old/new design, and index the measurements from the long shaft/prop end. That would place them approximately 1.63 in from the long shaft end of the outrunner housing. At first I thought we found something more profound, but it appears it is an artifact of the addition of the skirt bearing.

[Miles]

Came across this today - thought I'd post it here, in case there's anything to be gleaned from it.

[gwhy!]

Nice find Miles.
I think you just save my sanity ,
That anwsers some nagging questions that has been going through my head for the last 2 days....

[Miles]

Glad it helped

[gwhy!]

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

Burtie

Hi Burtie and Thud,

Burtie Your spot on with this spacing @ 17.14 degrees mechanical ... Its taken a while for me to get my head around because of your opening statement about the magnets, but thanks to Miles ( his pdf find ) the penny has finally dropped on a few things . Thud, possibly a better way of looking at it is 2 magnets = 360 elec degrees which = 51.42 degrees mechanical with these motors ( 14 magnets ) so working back we need 120 degree electrical spacing hence the 51.42/3 = 17.14 degrees mechanical. Sorry if everyone else has already worked this out but I am a bit slow sometimes.

Edit:
Miles, the information in that pdf have just solved another issue ( puzzle ) I'm having with a new controller, you sir are a Star

[liveforphysics]

Great .PDF find Miles

That defiantly needs to get filed in the technical area. Very helpful info in there.

[Miles]

Other useful papers where that came from.....: http://www.kth.se/ees/omskolan/organisa ... ts?l=en_UK

[Thud]

Thanks guy's,
I have a clear understanding of this method used to trick the controllers into thinking your halls are on 120 deg. The math will change if you use 10 magnets or 20 magnets. (once drawn in cad it is clearly understandable )

[JEB]

Maybe I missed it, is there a place that covered some final thoughts on adding hall sensors to a Astro 3210 motor? (inside motor, or outside magnets,and halls, 17.~ deg, 15, 120, ???)

Also, will any brushless sensored controller work with the 7500 rpm of the motor? Suggestions on the best one to use?