I was Just Surfing the net and came across Sensored brushless systems.
So what does that mean?

I'd think of two systems.

One is rotary encoder, like a servo.

The other is a hall-effect sensor in a brushless dc motor, that determines the position of the rotor w.r.t the stator, so that the appropriate signals could be triggered.
But instead, the principle of 'back emf' is used in the modern BLDC motors and ESCs.

Watch them all and you'll know.

I guess the second video has what you need to know.

Thanks!

Sensored for on, sensorless for off-road.

There's a lot more to it than on road and off road. It's really beautiful, all that tech if you learn more about it.

Quote from: rishabhbarma on February 15, 2018, 11:37:07 PM
Sensored for on, sensorless for off-road.

Could you explain it Rishabh? Not able to figure out.

Sensored BL motor : This motor is equipped with hall sensors which will detect the magnetic pole it is subjected to. This will help ESC to perfectly calculate the number of phase rotations as well as to switch the phases of motor.

Sensorless BL motor : Since these do not have sensors do detect the ESCs use separate algorithm to detect zero crossing of the motor. http://ww1.microchip.com/downloads/en/AppNotes/00857B.pdf
More info about zero crossing detection etc in the above link. 

So, is it using a timer or something like that Bala? The AN857 user manual is pretty long to read

Definitely I'll read it, but for right now, do me a favor & clear my doubt. Thanks

This is the good video to get you started.


They use timers to commute but not for zero crossing detection as zero crossing is not controlled by ESC rather it will happen inside the motor only which will be captured by ESC. This is also some times termed as back emf detection.

If someone is interested in building one ESC. You can check out this link.
https://github.com/bluerobotics/BlueESC

That was exactly what I was talking about

Quote from: Aravind298 on February 15, 2018, 08:21:38 PM

But instead, the principle of 'back emf' is used in the modern BLDC motors and ESCs.

Anyways, thanks for the links. Looking forward to make an ESC in the coming weeks.

@aravind,

Wrt rc cars, sensored systems are smoother at low speeds.. Hence for on road/crawling, it's preferred over sensorless. It performs better at lower rpm.

At higher speeds/off road- there isn't any difference, except sensored being less efficient. Hence sensorless.

So, the sensors are situated inside the motors? And how are they inefficient? Thanks

Sensors motors have hall sensor or also called as hall effect sensor which are used to detect position of stator which is then fed to speed controller. In sensor less motor as specified there are no sensor the position of stator if identified by using back emf also known as counter emf generated due to coils of motor as due to load (prop or gear). When there is no load on motor for full throttle motor draw less current as back emf is lessand at specified load it draw specified current at full throttle as back emf is greater.
This all done by ESC. In case is sensors motors hall sensor which is known as brain of ESC detect stator and this ESC works.
It is not point to discuss which is efficeient or better but i think hall sensor me get damage due to long terminado usage. This is what i know. Please correct me if I'm wrong. Thank you . Have a nice day.