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-   -   Brushless - Sensored vs. Sensorless (http://www.rcuniverse.com/forum/rc-electric-off-road-trucks-buggies-truggies-more-147/4175904-brushless-sensored-vs-sensorless.html)

long_tall_texan 04-17-2006 11:23 AM

Brushless - Sensored vs. Sensorless
 
Sorry if this is a re-post, but I couldn't find my direct answers by searching.

I am looking into upgrading to brushless on my T3. I need to get some elaboration on what I am looking at though. Not asking about prices. I'll decide on that after I have the technical details to way against it.

1. What is the difference between sensored and sensorless? I know that sensorless is supposed to be faster, but what else?

2. I know I need a new ESC for the brushless, but can a sensored ESC work with sensorless motors, or vice-versa? Wil the sensorless ECS work with my old brushed motors too?


studysession 04-17-2006 06:09 PM

RE: Brushless - Sensored vs. Sensorless
 
1 Attachment(s)
Sensorless will cost you more money. But it is more versatile than the sensored. I have both but love the raw power I get out of my sensorless stuff a lot better.

You can say I have a few brushless motors:;)

mycarisaser 04-17-2006 06:21 PM

RE: Brushless - Sensored vs. Sensorless
 
sensored brushless suck

DTAK 04-17-2006 08:48 PM

RE: Brushless - Sensored vs. Sensorless
 
if you dont want to run more than 6 cells, just stay with a sensored. you will not be dissappointed, because your t3 will fly with both. sensorless does have more power, but some people say its uncontrollable, and you can't run it without cogging with 6 cells or under. hope this helps.

-Inverted- 04-17-2006 09:10 PM

RE: Brushless - Sensored vs. Sensorless
 
The sensors on a brushless motor are usually Hall Sensors. These devices detect change in magnetic fields (a shift from North to South and vice versa). They are used to detect the position of the permanent magnet rotor inside the motor housing. Depending on how they are positioned inside the motor and how the rotor of the motor is designed, they may be detecting the actual rotor magnets or additional magnets (very small) inserted in the back end of the motor at a 90 degree angle with the actual magnets. With Aveox motors, these small magnets resemble small pills and are called ‘pill magnets’.

Before any explanation of the sensors is made, a fundamental understanding of motors needs to be developed. A motor functions on Faraday’s principle which states that when an electric current runs through a coil of wire it creates a magnetic field perpendicular to the coil. Based on this principle, you can essentially create a magnet out of a coil of wire. The advantage of this type of magnet over a permanent magnet is it can be turned on and off. Another variation of Faraday’s law states that when a magnet moves through a coil of wire, it creates an electrical current in that wire. This is how a generator works.

Now, imagine if you had a regular, permanent magnet sitting next to a coil of wire in such a way that the magnet’s south pole was closest to the coil. If an electrical current is passed through the coil in such a way that a north/south pole is created with the north pole being closest to the permanent magnet, then the magnet would move towards the coil of wire due to the attraction of the opposing poles.

In a permanent magnet motor, the permanent magnets are placed on the rotor and the coil wire (the stator) is inside the housing of the motor. In order to get the rotor to turn, we need to create a magnetic field inside the coil which attracts the poles. If the magnetic poles of the rotor are not aligned properly with the poles of the "created" magnetic field, then nothing will move. Therefore, it becomes necessary to know where the rotor is with respect to the stator. One way of knowing is to place sensors inside the motor which detect the position of the rotor with respect to the stator. Once this information is known, the motor controller can place the current in the correct coils of wire (motor phases) and create the desired motion. Once the rotor is in motion, the controller begins switching the current from phase to phase to create a rotating magnetic field which is always aligned with the rotating permanent magnet rotor.

There are other techniques of "‘sensing" where the rotor is without sensors. Three of them will be discussed here. One way is to arbitrarily place current into any two phases. There is no guarantee that the created magnetic field will be in the correct direction or position. However, it will be enough to cause the rotor to slightly move. The movement of the permanent magnet rotor in the stator, creates a back emf (electro motive force) on the stator wires. This back emf can be measured by the controller. Based on the value measured, we can calculate where the rotor is. This is at best a guess. If you have ever turned on a sensorless system and observed that the rotor moves erratically at first, you are observing the controller trying to get a reading on the position of the rotor.

Another method is to slowly start cycling the current through the motor phases. The slow speed allows the rotor to begin moving and to eventually fall into synch with the rotating magnetic field in the stator.

The third method employs the knowledge that when a magnet is placed inside a coil of wire, it affects its inductance. By knowing the inductance of the stator phases and measuring the change in them, the position of the rotor can be determined. This method works with a particular type of motor and is not very versatile.

Until fairly recently, the only way brushless controllers "knew" the rotor's position was by using three Hall effect sensors in one end bell of the motor. A Hall effect sensor gives off a pulse of electricity as a magnetic field changes around it. A small magnet attached to the

Sensors vs. Sensorless: Pros and Cons

So, how do you choose between the brushless controllers? First, if you have a sensorless brushless motor, which includes just about all brushless motors currently in production in Europe such as Hacker, Jeti, Kontronik, Plettenberg, as well as the little Astro Flight 010, then you have no option to choose a sensor-equipped controller. If those five little Hall effect sensor wires are not coming out of the motor, you must use a sensorless controller. The choice then becomes which one.

However, if the motor is sensor-equipped, such as all Aveox motors that I know of, Astro Flight except the 010, MaxCim motors, and earlier Kontroniks or Plettenbergs, then the option is open.

Here are some pros and cons of the two types based on my own limited experience and input I have received from motor and controller makers, as well as modelers who are more experienced with brushless systems than I am.

Sensor-equipped controllers:

Pros:

* Instant startup under any loading conditions, from no prop to light direct drive props to big props on soft belt drives.
* Very low minimum running speeds so a low "idle" speed can be set to facilitate landings and smooth operation across the full RPM range of the motor.
* Simpler software in the controller.

Cons:

* One motor per controller, increasing the cost of multi-motor installations.
* Controller from one manufacturer may or may not work properly with another manufacturer's motor.
* Potentially higher motor costs to include the sensors.
* More difficult installations as eight wires must be accommodated and the Hall effect sensor wires are often relatively fragile.
* Reversing motor rotation must be handled by provisions in the controller and may require physical retiming of the motor.
* Requires a sensor-equipped motor.

Sensorless controllers:

Pros:

* Motor timing is handled by controller software with no mechanical adjustments needed at the motor and may be tailored to motor and/or intended application.
* Reversing rotation is done by simply exchanging any two of the three motor connections.
* Simpler installation since there is no Hall effect sensor wiring.
* Possible to run two motors from one controller. I have not tried this, but have heard of successful installations.
* Potential for lower cost motors.
* Can run motors whether equipped with sensors or not.

Cons:

* Not all controllers will successfully start all motors and startup may be slow and/or rough.
* Startup also sensitive to motor load – some combinations of props/reductions won't start reliably.
* Higher minimum motor running speed may make it difficult to land a scale or sport type plane with the motor running (though this has been improving).
* More complex software.

Brushed & Brushless

One conclusion I draw in all of this from my non-competition minded perspective is that right now there is a bit more care required in matching brushless motors and controllers than for their brushed counterparts. It is probably impossible to know in advance whether a particular controller/motor/cell count combination is going to work smoothly or not, especially when mixing components from different manufacturers. You CAN pretty well expect that a Jeti controller is going to run a Jeti motor, or a Kontronik controller is going to run a Kontronik motor just fine. However, start mixing them up or using sensorless controllers with sensor-equipped motors and some care is required. Controller makers are continuously improving their software so that as time goes on this becomes less of an issue.

For example, schulze has recently released new software in the future series that they call the "super high performance algorithm" or shpa.

By the way, this sort of combination, a big load with soft coupling to the motor, is particularly challenging for a sensorless controller to get the right feedback from the motor when attempting to start. Another challenging load, I am told, is to attempt start up with little
or no load at all.

In addition, the motor must be turning at some minimum speed for a sensorless controller to be able to keep track of the motor rotors' position.

Certainly, the European market is going firmly in the sensorless controller direction, while US makers are still generally in the sensored camp.

As far as I can tell, choosing one over the other will depend as much on cost and availability as on whether they are sensor-equipped or not. The recent advent of the Jeti Phasor motors and their companion controllers has lowered the cost of a brushless system as low as or lower than a comparable quality brushed motor-controller system. However, I do not know whether the fact that these are sensorless systems has anything to do with the overall lower costs.

I also don't know whether the world-championship performance of the Hacker and Kontronik motors and schulze controllers has anything to do with their being sensorless. It certainly must not hurt, or they would be using sensored motors and controllers in those very high performance applications.

In any event, sensorless brushless controllers are clearly here to stay as a viable alternative to sensor-equipped brushless controllers.

R/C fan-addict 04-18-2006 08:49 PM

RE: Brushless - Sensored vs. Sensorless
 
[X(] that's a mouthful there caddy!!!! lol someone had a lot to say!

-Inverted- 04-18-2006 08:50 PM

RE: Brushless - Sensored vs. Sensorless
 
Quote:

that's a mouthful there caddy!!!! lol someone had a lot to say!
[8D]

dracohowe 04-18-2006 08:53 PM

RE: Brushless - Sensored vs. Sensorless
 
i think eh might have pasted it lol

Flyojumper 04-18-2006 09:01 PM

RE: Brushless - Sensored vs. Sensorless
 
Yeah that's a copy and paste...
You should have given a little credit to the author and original article found here (september 2001 article on brushless motors):
http://www.rcgroups.com/links/index.php?id=3846

_flyin_bryan_ 04-18-2006 09:11 PM

RE: Brushless - Sensored vs. Sensorless
 
studysession, dude, that is some seriously sweet hardware you have there, VERY VERY NICE COLLECTION!!!

-Inverted- 04-18-2006 09:53 PM

RE: Brushless - Sensored vs. Sensorless
 
Quote:

Yeah that's a copy and paste...
You should have given a little credit to the author and original article found here (september 2001 article on brushless motors):
I know, just didn't feel like typing it all out when I could just post that.

Flyojumper 04-18-2006 10:14 PM

RE: Brushless - Sensored vs. Sensorless
 
I completely understand that, but I still think a little line giving the article/author some credit would have gone a long way, especially since your shade/smiley face reply after R/C fan-addict's comment kind of implied that you were the one who typed it all...

_flyin_bryan_ 04-18-2006 10:35 PM

RE: Brushless - Sensored vs. Sensorless
 
ya, but what about studysessions arsenal there, that made pepsi shoot out my nose!


ps, studysession, we aint racin buddy, so forget it, lol. (my poor little velociti)

-Inverted- 04-18-2006 10:48 PM

RE: Brushless - Sensored vs. Sensorless
 
Quote:

I completely understand that, but I still think a little line giving the article/author some credit would have gone a long way, especially since your shade/smiley face reply after R/C fan-addict's comment kind of implied that you were the one who typed it all...
That was just implying that it was a long post, I don't type like that.

studysession 04-19-2006 08:29 PM

RE: Brushless - Sensored vs. Sensorless
 
I have a few speed car projects. I just love the power and speed that I get from my sensorless systems. A lot of people complain about sensorless because of cogging or what ever. If you do not set your system up correctly and use good battery packs, wire and connectors. Yes you will have issues. But if you take the time to learn and do it correctly. You do not have any of those issues.

Sensorless are really for the advanced user. Not the novice unless you are willing to invest the money and time to do it correctly.


Quote:

ORIGINAL: _flyin_bryan_

ya, but what about studysessions arsenal there, that made pepsi shoot out my nose!


ps, studysession, we aint racin buddy, so forget it, lol. (my poor little velociti)

mycarisaser 04-19-2006 09:49 PM

RE: Brushless - Sensored vs. Sensorless
 

Quote:

ORIGINAL: studysession

I have a few speed car projects. I just love the power and speed that I get from my sensorless systems. A lot of people complain about sensorless because of cogging or what ever. If you do not set your system up correctly and use good battery packs, wire and connectors. Yes you will have issues. But if you take the time to learn and do it correctly. You do not have any of those issues.

Sensorless are really for the advanced user. Not the novice unless you are willing to invest the money and time to do it correctly.


Quote:

ORIGINAL: _flyin_bryan_

ya, but what about studysessions arsenal there, that made pepsi shoot out my nose!


ps, studysession, we aint racin buddy, so forget it, lol. (my poor little velociti)

Amen to that brother. I have invested . I bought the best of every thing and man is there a differance. I tried out my freinds new novak 5.5 system the other day in a t4. He is using a 3300 stick pack. I run in my mf2 a mgm esc with a lehner motor and matched batts. Its like night and day differance even when I let him use a matched pack the novak didnt have the power or speed of my lehner basic 4200 and neither one cogges and they are just as smooth in throttle responce but on the flip side of that my systen cost twice as much as his. Well one main reason I went for the raw power of a sensorless systen is that I live on a beach with very large sand dunes(some over 175 feet) The novak system didnt have the power to climb all the dunes. I can stop half way up, start again and still get to the top without any problems. Also b/c of the strain on the novak system his battery died before mine and his motor and speed control got really hot ( we even put a smaller pinion in to help) Sorry to ramble but thats whey I go for a sensorless system. POWER BABY

_flyin_bryan_ 04-19-2006 10:28 PM

RE: Brushless - Sensored vs. Sensorless
 
ya, ive got some catching up to do, i got the gtb 5.5 and it is the fastest thing ive ever had, but ive been out of the hobby for a while and just figured the gtb system would be my intro into brushless, and i love it but now im seeing these sensorless units and am very interested in getting one, any suggestions on a system that would allow me to upgrade as i get better?

mycarisaser 04-20-2006 06:03 PM

RE: Brushless - Sensored vs. Sensorless
 
The 5.5 and gtb is a great system and is very fast. If you are looking for more power novak has the 4.5. Its the cheapest way to get it since you have alread invested in the system. I would love to see what it is capable of. Your system will run its best with good batts and you can run 7 cells for more power too.

The best system that I have found for power and smoothness is a mgm comp pro 120 speed control and a lehner 5300. I ran that system on 7 cell matched packs and 10 cell matched packs 45+ mph on 7 cells(I got it up to 52 mph on 7 cells ) My only problem with this set up is I would kill the thrust bearing plates in the diff in about 15 to 20 runs. But if you want power it has it. Also if you email rc-monster.com and ask them what system would fit you best need he can set you up. (note that the bk controllers have a start cogg problem( I have bought 3 of them) so go with a mgm its better)

studysession 04-20-2006 10:53 PM

RE: Brushless - Sensored vs. Sensorless
 
I have two BK controllers and do not have the cogging you mention. I have the 9918 & 9920 which are essentually the same. Only difference is one handles 18 and the other handles 20 cells.

mycarisaser 04-21-2006 10:27 AM

RE: Brushless - Sensored vs. Sensorless
 
I have the same ones and I also have the 7018 too whitch has the same problem. I have problems when I grab full trottle from a dead stop. Also the speed controller make the motor have lots of running noise were the mgm is whisper quite and silky smooth.

studysession 04-21-2006 06:06 PM

RE: Brushless - Sensored vs. Sensorless
 
Sorry to hear that. Slow or fast - until the batteries get week. I do not have those problems.

mycarisaser 04-21-2006 06:41 PM

RE: Brushless - Sensored vs. Sensorless
 
I have matched gp3300s and matched ib3800. I have also used lipo batts with the same results. I have heard that the bk controller are computer programable. I wonder if its a programming issue b/c I bought them all around the same time

bxpitbull 07-19-2006 02:20 PM

RE: Brushless - Sensored vs. Sensorless
 

Quote:

ORIGINAL: mycarisaser

The 5.5 and gtb is a great system and is very fast. If you are looking for more power novak has the 4.5. Its the cheapest way to get it since you have alread invested in the system. I would love to see what it is capable of. Your system will run its best with good batts and you can run 7 cells for more power too.

The best system that I have found for power and smoothness is a mgm comp pro 120 speed control and a lehner 5300. I ran that system on 7 cell matched packs and 10 cell matched packs 45+ mph on 7 cells(I got it up to 52 mph on 7 cells ) My only problem with this set up is I would kill the thrust bearing plates in the diff in about 15 to 20 runs. But if you want power it has it. Also if you email rc-monster.com and ask them what system would fit you best need he can set you up. (note that the bk controllers have a start cogg problem( I have bought 3 of them) so go with a mgm its better)
You couldnt be more incorrect. The one thing the Sphere/Sphere Competition has over the GTB is the ability to run 7 cells. NOVAK clearly states 4-6 cell operation. You may be able to get some burn with a 5800, but anything higher than that, when you start talking about the ".5's" (6.5, 5.5, 4.5) the amp draw is too high and you will burn up the speed control before the thermal shut down can even to THINK of engaging.

raz54 07-19-2006 08:38 PM

RE: Brushless - Sensored vs. Sensorless
 

Well one main reason I went for the raw power of a sensorless systen is that I live on a beach with very large sand dunes(some over 175 feet) The novak system didnt have the power to climb all the dunes. I can stop half way up, start again and still get to the top without any problems.
[/quote]









There must have been some thing wrong with that Novak if it couldn't make it up a sand dune, hell even my old havok motor could wheelie over one and my Novak flies over the top landing 8-10 feet away. I do agree though that sensorless has more power, too much for a novice and too much for a lot of trucks to handle (IMHO).

kingeric1991 07-20-2006 08:22 AM

RE: Brushless - Sensored vs. Sensorless
 
what does cogging mean ?


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