Sensorless 3-Phase Brushless DC Motor Driver 12A, 15000RPM, URGENT HELP

Thread Starter


Joined Jan 23, 2011
Hi All,

Could you assist me to build a sensorless motor driver please.
This is very urgent.


  1. 3 phase DC motor (E-max CF2212 datasheet)
  2. 11.1v nominal (3S lithium polymer)
  3. 0.15Ω internal resistance of motor
  4. Up to 15000 RPM
  5. Up to 12A

A pic will give analog (dac) output to determine motor torque (or simply current). And rest of drive process will be handled by hardware. I prefer to use seperate and small parts instead of combo driver ic's.

Please help me, assist me. Dont give me complex circuits that i cant understand. Please take it simple.


Joined Apr 20, 2004
It would be good if we had some idea of your background. Do you have any experience with electronics? How about programming?

What sort of hardware do you propose to use to do the speed control? Are you able to construct a PCB?

What sort of control are you attempting to use on the motor? You speak of determining torque (or current). How is the external hardware going to use that input? What is the "rest of drive process"? Are you planning on some input back to the microcontroller to make a control loop?

There seems to be some hurry-up on your part. Why is this so important to be done so quickly? Is this an assignment?
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Thread Starter


Joined Jan 23, 2011
Hi again,

I'm an electronics engineering student and this is a part of my project. Yes, my programming is good and electronics knowledge is not bad. Yes i can draw a pcb. But the matter is, i've never designed a motor driver or take lessons about motors at school. I've 10 days, that's because i must hurry :)

And there is no need to a loopback. Pic will give 0-5v DAC (i can handle this part) and the circuit that i asked for will drive the motor.

By the way, i need a simple driver. But it shouldn't fail and hurt lipo's or blow the motor.

Waiting for help.
Thank you!
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Joined Nov 7, 2008
Driving a sensorless bldc motor is not a simple game!

You will need three separate half bridges for driving the three windings, an analog mux driven by the pic to measure the EMF generated from the undriven windings with an ADC channel of your pic, to establish rotor position and speed and be able to synchronize the three half bridges.

Good luck

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