Brushless DC Rotor Position Question

[benjaminbailes]

Hi. I am curious about ways to sense the position of a rotor in a BLDC motor. I am familiar with hall sensors and back emf but am wondering if there are other ways to find the position of a rotor maybe more accurately.

I had an idea about using a laser and a photoresistor around the circumference of the stator that would use the varied resistance to give a voltage reading to a microcontroller that could be used to find the position. Maybe I'm way off with that one I can see some problems like heat from the motor messing with the resistance. If anyone could give me some suggestions on what's out there I would appreciate it.

 

[I_am_learning]

They are called rotary encoders.
http://en.m.wikipedia.org/wiki/Rotary_encoder#section_5

 

[benjaminbailes]

They are called rotary encoders.
http://en.m.wikipedia.org/wiki/Rotary_encoder#section_5

Thanks for the tip

 

[Turst]

Resolvers are also useful for absolute position.

 

[alphysicist]

Hello! Your question about finding the position of a rotor in a brushless DC motor is a great one. Hall sensors and back emf are commonly used methods for sensing rotor position, but there are also other options available.

One possibility is using a resolver, which is an electromechanical device that can accurately determine the position and speed of a rotating shaft. It works by using a rotor and stator with multiple windings and measuring the inductance and capacitance changes as the rotor rotates.

Another option is using a magnetic encoder, which uses a magnetic field to detect the position of a rotor. This can be a more precise method compared to hall sensors, as it can provide continuous position feedback instead of discrete signals.

Your idea of using a laser and photoresistor is also interesting. While it may face challenges with heat and potential interference, it could be worth exploring further as a potential solution.

I would also suggest looking into sensorless control techniques, which use mathematical algorithms to estimate the rotor position based on other motor parameters such as current and voltage. This can eliminate the need for physical sensors and potentially provide more accurate results.

Overall, there are various methods available for sensing rotor position in a BLDC motor, each with their own advantages and limitations. I recommend researching and testing different options to find the best solution for your specific application. Best of luck in your research!