Yeah, sensorless systems are significantly more efficient. The reason is that the controller can vary timing based on RPM, load, etc. and uses the OPTIMUM timing at all loads and RPMs.

With the sensorless startup algorithm we have, there is no need for sensors unless you are doing something like rock crawling -- so why have the reliability issues of the additional wiring harness and PCB, AND the additional cost?

Don't fall for the BS Hype -- sensored is worse in almost every way.

Now for rock crawling, where the motor needs to have torque when not rotating, sensored has a slight advantage.

You missed my point about the Speed Passion GT ESC though. It combines both worlds. Apparently, if you run something like a Novak on this ESC, it runs far better due to the variations in timing that the ESC can select, like you say.

I don't understand how having sensors creates reliability issues? I have an original SS5800 motor that's still going strong. It's been run on anything from 6 cell Nimh to 2s lipo to 12 cell Nimh. No problems yet and the motor has to be a few years old. I've read of the odd problem with a Novak motor here and there, but in comparison to some other motor issues, it's not NEAR as prevalent. Sure, more parts means a higher chance of failure, but for the sheer amount of motors they have out, I've only heard of a few reports where the motor was messed up due to sensors.

I'm sorry, I didn't miss your point. I'm saying there is no reason to run sensors AT ALL. Adding sensors to a motor / speed control has no benefit, and proven drawbacks, so why do it?

Reliability issues are because of additional small wires that can get pinched, broken, fatigued, etc, as well as an additional PCB in the motor that can get damaged or fail. More failure points in the system, lower reliability.

To each their own I suppose. I figured you missed it since you mentioned nothing of that particular ESC.

Why is there no benefit to sensored? Wouldn't that give the ESC an advantage for performance if you could come up with software to take advantage of it? I would assume the more information the ESC knows for sure, the better.

No, because the sensor data is arbitrary to timing -- this is another reason why sensors are a bad idea -- the controller has no idea how much advance the sensors have. Also, usually there is some phase skew from sensors as well -- so that upsets timing as well. As the saying goes, Garbage in, Garbage out...

Adding sensor data to sensorless data would actually make timing worse, and reduce efficiency...

I have a sensored 1/10th scale system from another vendor & I can say for sure. There is no more cogging in my MMM/Nue set up than in that other vendors system. On top of that the MMM is WAY more programmable than that other system as well. Before I ran the MMM, I was worried about cogging but now that I have run the MMM, the subject of cogging does not even come into my head (unless you guys post something about it).

Besides, a lot of what is commonly referred to as cogging is actually not cogging and lack of power or various other things.

I will disagree with you, Patrick, about sensored motors, and there is no "Hype" here. For given application there is a given motor.
Brushed motors can deliver 1000% torque at stand still
Sensored Brushless motors 1/3 of that
Sensoreless not even 20-30% of that sensored systems
You know why and there is no BS here.

Extra wires and sensors are weak links as well as brushes, as long as mentioned them.

Timing with sensors can me more advanced and flexible if you write software accordingly and there is no need to set sensors exactly at "0", you can adjust it anytime as wide as you wish. And back check with motors efficiency, you can even run in dual mode and use sensors for back-check, startup, pulling, holding and braking. If you creative you can even generate brushed mode. Just need to set sensors perfectly spaced to motor poles. If you use encoder instead of hall-sensors, or even IC you can be completely independent of motor type/pole count. I am not going too deep in details, but I think you know the rest.

All the rest about sensored systems in only limited by flaws in software.

I actually was saving this sensored idea from suicideneil for desert, but I guess it would be impossible to convince you otherwise... :(

To BrianG:

Brian, I wasn't expecting question like that from you. Efficiency curve defines given motor RPM range. Number of Poles, Motor diameter and rotor length defines torque and speed factors. (Rotor weight, air gap, core material, windings, delta/star...) From motor parameters you can plot it quite easy.
For the same Power motor with
More poles -> Lower RPM Higher Torque
Less poles -> Higher RPM Less Torque.
Smaller diameter -> Higher RPM, Lower Torque
Bigger diameter -> Lower RPM, Higher Torque
Longer rotor -> Lower RPM, Higher Torque
Shorter rotor -> Higher RPM, Lower Torque
I do not even know what to comment on "Less" EMF pulses...
I will call it Monday and I am in bad mood and picky, sorry for harshness.

Artur, I already "know" what the answer is, but thought it would carry weight if it came from a designer of the product. I'm just thinking forward to when CC starts carrying their MMM and motor combos.

I see a lot of people running kinda low rpm setups and gearing almost too high, and also the occasional startup cogging.

Sounds like someone has a case of the Mondays! (Office Space reference in case you didn't get it :wink:)

From a typical R/C use standpoint, sensorless commutation works well enough. As Patrick pointed out Rock Crawlers could certainly benefit from a sensor, but I can't imagine any way that it would improve performance anything else out there in the ground market (besides tall rollout 4 cell nimh carpet racers).


Boy what I wouldn't kill for a sensored outrunner system. Maybe in one year.

I'm going to disagree with you here. Sensored motors are marketed with a lot of HYPE -- The makes of sensored systems have been BSing the public for a couple years now, telling them that sensorless is inferior, in the hopes that people will buy into their hype. And some people have bought into the hype.

Try this: Take a sensored motor and measure how much phase imbalance the sensors have -- you'll be astonished and shocked at how BAD the sensors are. Typical sensor phase imbalance is around 10 degrees from sensor to sensor, and that's just PHASE imbalance. Even on high-end military motors there is at least 5 degrees of phase imbalance -- just because Hall sensors trigger points aren't precise. And timing itself is completely ambiguous with a sensored system - - and because it is ambiguous, it can't add any meaningful data to the rotor position estimate.
Not only that, but sensors also trigger incorrectly all the time during run (by winding flux) -- and the sensor controllers blindly follow the incorrect sensor outputs...

Granted, sensored systems can produce more torque at stall than sensorless systems. But in RC applications we can generate more torque at startup than is required using only sensorless algorithms.

You state: But that really isn't true. Once the sw PLL is locked (within a few commutation cycles) we can control timing to within .1 degrees -- how can an ambiguous sensor system with jitter and phase imbalance add to that? Adding sensors into the equations just makes the position data LESS precise.

Believe me, we build hybrid controllers (that start sensored and run sensorless) for both the military and industrial applications, and have been building those types of controllers for years.

We've done all the math, the simulations, and modeled the systems extensively. Once the sensorless software is locked, sensors add nothing but noise to the system.



Sensors are useful for generating a lot of torque at stall (> 20% PWM duty cycle lengths), but with the motors we use in RC, we can't even PWM at 20% during stall -- they would draw thousands of amps. So even at a 20% max duty at stall we can generate PLENTY of torque at startup -- Seen the videos of people backflipping Monster Trucks with the MMM from a standing start? :smile:

So there's my rant about sensors. With respect to timing and control, Sensorless = precision, Sensored = ambiguity.

Ok, so I've kinda got the "Mondays" myself. 'Cause I have to get up at 5:30am to fly to California. And I don't want to go to California.
And it's been raining here a lot, and my backyard is flooding and mulch is pouring into my pool and I keep having to spend hours cleaning it out.
And I got an E-Revo and I haven't even had time to install a Monster in it yet.

And I keep editing this post 'cause I don't want people to think I'm angry or being aggressive about this... I just want to present the facts...

I must be the only person who had a pleasant Monday...:lol:

my monday was fine. the only thing that is getting me down is Pdelcast has an e-revo and I dont (haven't even heard of traxxas shipping yet). :mdr:

luckily my job allows me 4 days off at a time :mdr: ..... anyways all this extremely deep electric talk was just basically bathroom reading until i saw that patrick has an e-revo .... :yipi: ...:surprised: ....i want one:no:

I don't know all the fancy shmancy terms and techno-blurb, but I have a lot of experience with a lot of controllers. Sensored USED to be better. It was not hype, it was fact. A year or more ago, sensorless simply was not as smooth, especially at low speeds. The sensored-smooth advantage is all but gone now and I won't likely buy another sensored system myself. There was a time though, that I wouldn't even consider sensorless because of the rough initial acceleration.