Applications of Sensored vs Sensorless Brushless Motors

How does a Sensored brushless motor work in comparison to a Sensorless Brushless Motor?
In a sensored motor, as the name implies, there are sensors that are positioned in the motor to send rotor position information back to the ESC. In a sensorless brushless motors, the ESC relies on what is known as back emf. Back EMF is essentially a voltage "Signal" that is sent back to the ESC in order to determine the position of the rotor.
Advantages of a Sensored Brushless Motor include smooth transition from slow speeds. Sensored motors are also able to produce a great amount of torque right at zero RPM. Sensored motors may contain a temperature probe that is located on the sensor board. In this case you are able to log motor temperature depending on the ESC and its capability.
Advantages of a Sensorless Brushless motor include being able to operate very well at high speeds. So well in fact that some sensored setups have a hybrid mode that operates in sensorless synchronization at high speed. Added reliability of the system in general is true when the extra sensors and components are eliminated.
Applications of Sensored and Sensorless Brushless Motors
Rock Crawlers are a perfect example of a type of RC car that must use a sensored setup. Other RC applications such as RC boats, airplanes, helicopters and drones do not require sensored motors. In fact a sensorless motor work very well.
Can a Sensored Motor work with a Sensorless ESC
A sensored motor operating on a sensorless ESC is completely possible. Expect the motor to behave much like a sensorless motor.
#SensoredMotor #SensorlessMotor #RCexplained

[@donmichaelcorbin4417]

Dude is a RC God, just look at his halo! Great video, very informative. Like and subscribed.

[@RCexplained]

Thanks for the sub!

[@PhillipGriffin3211]

I see the halo

[@westernsharpie]

6:50 is the answer I needed

[@RCexplained]

Excellent!

[@kennethabela8209]

Brother! I know everything you said.....BUT....I really need to congratulate you on the manner you manage to explain stuff! Absolutely perfect! Enjoyed watching every second. Cheers.

[@RCexplained]

Hey Kenneth, thanks for the awesome comment. Truly appreciate it!

[@michaelneal7079]

I've always had nitro buggies, got some electrics for the kids for Christmas and are lost with all this new lingo , your videos are great , comprehensive... thank you

[@RCexplained]

Hey Michael, thank you for your comment! I hope your kids love the electrics that you got them! Let me know how it goes!

[@TejasToolMan]

same here im switching from nitro 1/8th since the late 80's to 1/8th truggy 2200kv, so much to learn on this. lol neighborhoods grown bigger can't run muffler less OS 21 maxx wide open all the time

[@RCexplained]

@@TejasToolMan You will not be disappointed with electric.

[@michaelneal7079]

@@TejasToolMan electric has been fun, losi mini 8t on 3s, but nitro will always be king , the sound, the smell ,getting that perfect tune, worst part of electric is battery maintenance, get a good charger and quality batteries

[@matthewscheiper6973]

Thank you so much for an outstanding video! Really helped me with my motor selection!

[@superjimnz]

To better understand the back EMF, it is useful to understand that at any one moment only two of the three motor wires have power flowing through them. The third wire is the one that is measured to determine what the motor is doing, as the motor acts a bit like a generator on that wire (back EMF). This is also why sensorless motors work poorly from stopped or at slow speed, because when the motor moves very slow, the "generator" effect that creates the back EMF is too small. In those cases the controller has to simply guess the position of the motor, and commutate blindly until the motor moves fast enough to provide feedback.

[@patrickmckowen2999]

Good vid I did a speed controller for final project in college -- damn back emf was burning out my FETs 🤣 Cheers

[@RCPhysics]

Great video as usual!

[@RCexplained]

Thank you!

[@joshriver75]

Great explanation! Thx

[@RCexplained]

Thanks for the comment!

[@davidgaleski5303]

thank you

[@pants7241]

Thanks!

[@moviecell1335]

Tq sr. Very informative.

[@kyangsable]

subscribed. great video quality.

[@RCexplained]

Thanks for the sub!

[@luca_rc_doc]

Thanks for you explanation! I'm struggling to find a good combo brushless waterproof (splash) motor/esc for my Tamiya XV-01. It has frontal motor, very long motor cables (and sensor cable) need to reach the esc. I'd like to use a 13,5 t motor with 3s lipo. Do you know where could I find some information or do you have any suggestions? Thanks

[@RCexplained]

Hi Lucadoc, thank you for your comment. I would suggest jumping on to a forum and posting your question on a Tamiya XV-01 thread. I'm not familiar with that Tamiya model.

[@luca_rc_doc]

@@RCexplained Hi Ryan, I'll go on the Tamiya USA forum, thanks

[@preetamsahoo9430]

Nice one!

[@RCexplained]

Thank You preetam sahoo!

[@RcOffroad9513]

Great info! I have always heard that the motor draws from the esc rather than the esc sending pulse? If you could clear this up for me I would appreciate it. Thanks

[@RCexplained]

You squeeze the trigger on the radio and the receiver sends the signal to the ESC. The ESC is responsible for taking that input and sending it to the motor. The ESC is able to produce a voltage at a frequency and when the motor receives the voltage at a specific frequency, it begins to rotate. The current draw is based on the load of the motor. A higher load on the motor and it will pull more current from the ESC. Example: The ESC changes the frequency of its output to speed the motor up, the motor as a result draws more current to handle the additional load. I hope this helps.

[@cgray86]

@RCexplained, is there a simple bench test I can perform to confirm the sensor is functioning as expected? Beyond that, can you share a solid method for tuning/adjusting timing on a sensored setup? I love your technical videos! Thanks - CG

[@RCexplained]

You could find the pin outs of the motor sensor cable that lead to each sensor and use a multi-meter to bench test. There are also motor analyzers available. My charger, although I have not used the function yet, does include a function that will allow a sensored output in to the charger for testing. Almost forgot, to adjust timing, I start in the middle and choose to go either low or high based on my goals. I am looking at a data log and speed generally. I want to confirm that more power consumption results in actual measurable performance gains if going to higher timing, otherwise there is not benefit.

[@foellerd]

Lol, that sounds like so much overkill. The motor will cog like a sensorless motor if the sensor wire isn't being used/isn't working. The point of the sensor is to not have motor timing be an issue; no need to set timing in sensored setup, does it automatically and exactly.

[@Otiesh]

Nice video, I have Known some thing and I hope next time you bring us a topic on smart ESC vs censored ESC

[@RCexplained]

Noted, thanks for the comment!

[@joxxla]

hi, great explanation, may I ask what 1/8 scale buggy are you using now? I'm looking to get a tekno 2.1 but it looks like I can't fit a castle 1515 with sensor loom. looking for an 1/8 scale buggy with more room to grow. Thanks!

[@RCexplained]

Hobao sse

[@saint4627]

Thank you i hope you also do rc drifting videos!

[@RCexplained]

Thank you for the comment. What kind of rc drifting video? My skills in drifting are quite weak.

[@saint4627]

@@RCexplained Some rc drift events would be nice. or rc events in general its nice to see updates on different rc events.

[@karlasch5475]

Hi Ryan! Nice video, but could you explain why sensorless mode is more efficient than sensored mode in a hybrid ESC? Because you already carry the disadvantages of the sensores with you (weight, cost, risk of mechanical or thermal damage), so why not use the sensors if they are already there? Wouldn't they be more accurate than the interpretation of Back EMF, even at higher rpms? Thanks!

[@RCexplained]

Hey Karl, thanks for the comment. You would expect the sensors to be more accurate as they are a direct measurement. But that is the actual problem. They are located in the same spot regardless of RPM. Much like in a car, you want to change the timing as the engine speeds change. Valve timing and ignition timing are altered. In a brushless sensorless ESC, the timing is done electronically to optimize performance in the exact same manor.

[@karlasch5475]

@@RCexplained Hi Ryan! I understand, that's the timing issue you are referring to. But wouldn't it be a piece of cake fir the ESC to take this into consideration? IF RPM>x THEN justAddSomePreIgnitionDegrees? In many ESCs you can set the timing, which is, I suppose, fixed through the whole RPM range (correct me if I'm wrong). On certain ESCs you can also enable a boost mode, which is, I suppose, a _dynamic_ timing. Not sure if this boost mode is only available in sensored mode ... And if you derive the rotor Position from back EMF, shouldn't you encounter the same problem?

[@RCexplained]

Hey Karl, I don't think it's as easy as simplifying it to a formula like that. When ESC's didn't have an auto timing advance function, the timing was set manually. Default would typically be a medium timing advance, however manufactures of ESC's would provide their recommendation in terms of how many motor poles are on the motor. As the number of poles increases, the timing advance also increases. A Wye wound motor vs a Delta wound motor will have a different timing advance as well. You would not be able to get motor poles and winding termination type in to your formula. These are only a couple pieces of the timing puzzle for electric motors. Take a look at what Castle Creations describes as their Smart Sense technology. They don't just state transitioning from sensored to sensorless at high RPM's is more efficient, they state that it is ultra efficient.

[@druscanam]

That's good. One topic I feel needs some illumination which you seemed to skip over and that's stock racing. We know that 4 poles gives you more torque then two poles and that for power sensorless is better. However stock racing motors all use two pole sensored motors. From my understanding two pole motors can achive much higher rpm then 4 pole motors given the same running voltage and number of motor turns, given stock class is restricted the number of motor turns you cannot go below as well as being restricted by voltage of 8.4V (2S) and although a 4 pole motor can achive more power and just as much rpm it requires either lower motor turns and or higher voltage to do so that are outside regulations permitted in stock class. Also from my understanding the main reason for them being sensored is to offset the lower torque usually associated with two pole motors and to help them run smoother with a more liener power curve. Anyways would be good you could actually make a video on this as most people just seem to accept that stock class motors are two pole and sensored without really understanding why.

[@jamesthornton642]

Hey Ryan it would be awesome if you did a video showing the difference between sensored and sensor less with an rc car

[@RCexplained]

Hey James. Great idea. I'll see what I can do.

[@gees5563]

Great video I have a question with a sensor motor all I have to do is plug my sensor wire in the ESC and Motor After that it should work fine I shouldn’t have to do anything else is that correct? Thank you

[@RCexplained]

Thanks for the comment, yes that is correct. If something is not working as expected, check the settings within the ESC to confirm it is operating in sensored mode.

[@gees5563]

@@RCexplained ok thank you 👍

[@gschaaf713]

hybrid mode is like the VTEC of RC

[@RCexplained]

Sensorless mode also since the ESC is constantly changing timing based on many parameters.

[@ameliabuns4058]

are bldc motors good for applying constant torque or do they heat up and have bad efficiency there? can they be used for low-rpm yet high torque applications without gearing it down? I couldn't find a proper answer when I googled :c

[@RCexplained]

If you use a controller that gives you constant torque, a BL motor will handle this no problem. You can get a motor with a very low kv that will operate very well at low RPM with ridiculous torque.

[@ameliabuns4058]

@@RCexplained :O thanks. most of the motors i found were something like 130KV and drew like 10a-5a at 12v D: also the torque I found was something like 1.9N.cm. a stepper gives me 10N.cm at a much lower wattage! I think I'll just use a stepper regardless. they're kinda bulky tho. maybe I can do a 10:1 gear ratio or something with the BLDC

[@CharlieSolis]

So if I were to be using an RC car BLDC motor as a generator, is there anything I should be worried about 1) using it in general as a generator and 2) if it is sensored? Like does using a sensored BLDC motor as a generator have issues because of the sensors? Would there be advantages of having the sensored motor especially while using it as a generator? (I do know they have to be spun at very high RPMs to get appreciable power out) Thank you you for your videos! They’ve been very informative!

[@RCexplained]

I don't see a reason to use a sensored motor as a generator as they are more costly. You can and just not use the sensors. A low kv motor will not have to spin all that fast to produce a voltage.

[@CharlieSolis]

@@RCexplained ok that’s good to know thank you! This may be an obvious question but are the sensors in the motor just position feedback, like a Halbach array, or do they also include things like internal temp read out and other things? Also If they give position feedback can that sensor be used for giving a read out of the exact positioning of the motor in degrees from some origin position or is it just position relative to the nearest coil and magnet alignment? oh also I’m ok with the high RPMs 😁 I’m going to be driving it with my Tesla turbines which will be able to do 25k-65kRPM. I actually specifically want the high rpm ranges. I was going to say take a look at the videos I’ve made of my Tesla turbine and ask you if maybe you had a suggestion of a good BLDC motor that I should use as a generator but I didn’t want to come off sounding like I’m trying to push my channel. I just genuinely would love to know your opinion on the generator side of things on these great little BLDC motor/generators. I watched your video about the regenerative breaking within the esc and I thought that was amazing to know and I almost thought I could just use that for my whole system but alas the efficiency of the esc rectifying the 3 phase to dc was lower than I would like for practical application as a generator. I plan to use my esc and RC car remote to aid the turbine to get passed the starting cogging torque for using the BLDC motor as a generator because Tesla turbines have low torque at low RPMs, so the throttle alone won’t be able to get the turbine and generator up to speed. But they work great once up to speed so once at running conditions, 25k-65krpm, I was going to give complete drive torque to the throttle on the turbine and cut the power from the esc and (carefully) connect the motor wires to a 3phase ac to dc rectifier to get DC power out. I acquired a cheapo GoolRC 3660 3800kv waterproof BLDC to do a test for the power output capabilities. The description says it’s rated at 1200w, 92 amps with 13v @ ~50krpm. (And I’m sure this thing may be rated for higher than what it should be run at continuously also) so I know that at 50kRPM to get 1.2kw (1.62HP) you only need to supply 0.2ft-lbs of torque in general for any thing as thats just the basis of mechanics as a force at a distance of rotation over a rotational distance is equal to work done, so obviously considering efficiency loss it’s a little more than that in real life but is this directly translatable to how much torque I would need to put into this 3800kv BLDC motor at 50kRPM to get the 1.2kw out, at 13v and 92 amps? Kt=1/kv = (1/3800) = 0.0002631nm/amp or .000194ftlbs/amp (.000194ftlbs/amp)*13amps = .002522ftlb for 13amps.....? Which is far lower than the 0.2ftlbs needed for 1.2kw at 50,000rpm, when it’s supposed to be 13amps at 92volts... What am I missing here...? Forgive me if this more complicated of an ask than you’re looking to offer, you’ve already answered a bunch of questions for me so thank you for your time either way! If you have a patreon I’d be happy to donate to pick your brain on the topic for a little you’re up for it. Let me know thank you!

[@RCexplained]

Hi Charlie, yes the sensored motor can have a temp readout as well. This depends on the motor. Your 0.2ftlb does not consider the efficiency of the motor operating at 1.2kw. 1.2kw is the input to the motor not the mechanical output. Don't forget about this. You also switched your volt and amps. Multiply Kt by 92 amps not 13V.

[@CharlieSolis]

@@RCexplained oh derp! Thanks for catching that. I knew I was making a stupid mistake somewhere when I was multiple orders of magnitude off. And perfect that helps! Because I was wondering if I could just get a BLDC motor/generator that has a built in temp sense that I can keep an eye on while generating power. It just makes implementing it within my system that much easier and safer. For real thank you you’ve been a great help!

[@CharlieSolis]

@@RCexplained ok yeah so with a resistance of .0083ohms and a 92amps at p=i^2*r that’s ~70.25watts copper losses and with 13volts and an Io of 4amps that’s 52watts iron losses, yielding ~122watts loss at 1.2kw in with 92amps at 13v-50,000rpm. 90 percent efficient is dang good in my honest opinion for a $30 BLDC. Obviously I’m sure there are way better. Especially when I can actually reuse the heat loss in my heat recoup system. Should I expect the same kind of 90% efficiency and losses while using it as a generator or are there other components to this that I’m not considering?

[@lazyman1011]

Super! Abo &Bell&Thumb see ya next time.

[@jakubp1790]

@RCexplained, you explained very clearly why sensorless motors have problems with starting at high load, but what is going to happen when the start is light, and then the load gradually increases, to the point that the motor speed drops to 50, 30, or even 20% of nominal speed? I am talking about a load progression similar to what an electric screw driver experiences. Will the sensorless motor stall much earlier than sensored? Will it stall at lower torque? Will it also become noisy and shaking before stalling completelly?

[@RCexplained]

Dropping speed due to loading is not necessarily a problem. Dropping speed below the minimum required speed to stay in synchronization is key. This RPM is quite low and you can test this with any RC car quite easily. The ESC needs to have feedback from the motor to stay in sync. If the speed is too slow the motor will stall.

[@jakubp1790]

@@RCexplained I think you are refering to sensored motor, right? I would be interested to know what is going to happen to a sensorless motor in these circumstances, that is increasing load and consequent decrease of speed. Since ESC does not know what the momentary motor speed is, I presume it will keep running at the same frequency, despite the increasing load and decreasing motor speed. Does it mean that some kind of slip will occur every n-th revolution, the more often, the more the motor speed differs from ESC frequency? Will it then just stall suddenly, or will some kind of precursory cogging/jerking occur first before the complete stall? At what percentage of nominal speed (or free running speed) should this be expected to happen typically?

[@RCexplained]

My reply was about sensorless motors. The esc does know the speed of a sensorless motor when it is spinning above the minimum backemf threshold. Above this speed 0 slip. A sensored motor would be 100% in sync from 0 rpm to max. Once a sensored motor starts spinning at a moderate speed most ESCs will ignore the sensors and then run in sensorless mode.

[@RcTilDeath708]

Can the Mamba Monster X 8s operate in sensorless mode?

[@RCexplained]

yes

[@mikeEshroom]

does it make a difference with braking?

[@RCexplained]

I do not notice a difference.

[@kelvinsmith406]

My sensor wire makes my rig only go in reverse but when I take it out it runs fine but runs TO HOT really quick...PLEASE HELP?

[@mohammedeldaly5645]

My car is cogging when i bought the new ESC So in the slow moving the motor it make some hesitating What should I do to stop this hesitating please

[@RCexplained]

try something here: kzbin.info/www/bejne/g2POaISipL2JhNE

[@tyladube801]

I'm just wondering is it possible to run a sensored brushless motor on a unsensored esc?

[@RCexplained]

yes, the sensored brushless motor will operate in sensorless mode. (sensors will not be used)

[@tyladube801]

@@RCexplained yea cause I have a reedy Sonic 540 6.5 turn sensored brushless motor and I'm getting a 120A esc shipped to me soon from wish. But yea just one last question what do the sensores usually control cause the esc I had connected to the motor would go full throttle on barely a quarter of throttle pull and the braking function for my motor would be fully engaged so the tires would stop spinning almost instantly so idk what the cause was for that but my rustler at the time got ran over by some #$$hole who knew it was there and nothing was done about that but I got my rustler all fixed up and set for a new esc to be put on it

[@RCexplained]

Hi Tyla, that's unfortunate about your rustler. Glad you have it fixed up. The sensors job is primarily to allow the ESC and motor to get in sync starting from 0 RPM. A sensorless motor would hesitate upon acceleration from 0 RPM. Once the RC is moving this goes away very quickly.

[@brianpumphrey8761]

Sensored for drift car or sensorless be ok?

[@RCexplained]

sensorless will be fine for a drift car.

[@HAWKONER]

So for wheelies and donuts/slides sensored?

[@RCexplained]

It will help if you plan to do those from a full stop. If you are already rolling, sensor less will work fine. Any speed above a very slow crawl, sensor less will be fine.

[@HAWKONER]

@@RCexplained That helped. Thanks.

[@RCexplained]

@@HAWKONER no problem

[@annmatiskam4571]

You can also do it with sensored, the sensor works when you climb things at slow speed

[@standbyme6395]

Can you make a sensorless motor work with a sensor esc

[@RCexplained]

Some sensored ESC's can operate in a sensorless mode allowing the sensorless motor to be used. This is ESC specific.

[@standbyme6395]

@@RCexplained that's what I was afraid of. Thanks for the response.

[@tobydyes]

Can you run a sensored motor on a sensorless system

[@RCexplained]

You can run a sensored motor on a sensorless ESC. The overall system will behave as sensorless.

[@mackattack8627]

Depends on the quality and type of motor a Lehner 3080 sensorless inrunner with ironless core are the smoothest and most powerful rc/industrial sensorless motor on the planet super smooth instant torque from start to finish it also depends on the quality of the ESC most of all - Kontronic,Mgm,Vesc or a quality ESC that have FOC some Outrunners of less quality and build will not sync with some cheap ESC,s that cause that glitch on load start up but will run ruffly and make a wine or humming noise while in rotation a good ESC smoothes all this out by being able to read the rotor position in hundreds of miliseconds but those ESC,s are not cheap and mainly only German made besides the Castle Creation 160hv that sync well with sensorless inrunner/outrunners

[@RCexplained]

Lehner motors are excellent motors indeed.

[@Krayziebone456]

So for a traxxas trx4 bronco crawling on obstacles sensorless would be best??

[@RCexplained]

A sensored system would be best for those initial starts from 0 RPM. I would recommend a sensored system as it sounds like you will be playing in the very very low speed range.

[@yashmadkaiker1360]

Can a sensored motor be used in sensorless ESC ?? , I won't be using the sensor wires from motor !!!. Is it possible ?

[@RCexplained]

Yes that is possible!

[@yashmadkaiker1360]

@@RCexplained any link where I can get proper explanation of this ?

[@RCexplained]

@@yashmadkaiker1360 I'm not sure of any. The concept is that any brushless 3 phase motor can run off a sensorless esc. Sensors are simply an added feature and are not required.

[@mrwaffleboy99]

Will you still get the sensored affects using that setup? Sensorless esc and sensored motor.

[@tylerbailey8834]

@@mrwaffleboy99 no it'll act like a sensorless because the esc is sensorless and thats all it knows how to do

[@mehimrc1314]

Great thumb nail then not one demonstration just lots of information without any visual references. I watched your ESC temperature video same again great thumb nail but then where was the demonstration or visual like the thumbnails

[@RCexplained]

Thanks for the comment and constructive criticism. I've been working more and more on getting visuals in to the video. Had to learn a lot to be able to do it as my expertise are not entertainment and video editing. Still a ways to go.

[@phillipjacobson4457]

I would think any moving object trying to overcome gravity of planet earth needs high startup torque. Once the motor overcomes gravity then the torque and amp flow decrease.

[@remkojerphanion4686]

Every Saturday evening I become senseless :)

[@mikeEshroom]

does it make a difference with braking?

[@RCexplained]

Not that I have noticed.

[@annmatiskam4571]

Nah,