Hi there,

I got this Brush less DC motor out of an dead HDD ..after making certain measurements and experiments,I found out that it is Sensorless Three phase motor with a ground connection at center i.e the coils are arranged in Star Formation!

I read about this type of motors and found out that since its sensor less it needs to detect the back emf on each coil to track rotor location and change supply phase appropriately. I tried to run it using atmega16 with L293D driver, shifting phase at regular intervals through 3 of 4 half bridges but none worked! There's lot of vibration and very low efficiency.

Can anyone please explain me how do i use the atmega 16 to run the motor? how do i get the back emf feedback to the atmega?

 

Search for applications notes by not just Atmel, but other microcontroller manufacturers. I can list a few, and they go into detail about how these motors work, and how to control them with their products. They are very useful and resourceful documents.

Here are a few, but you can do a search yourself and find many, many more from a variety of MCU manufacturers.

AVR443: Sensor-based control of three phase Brushless DC motor

AVR498: Sensorless control of BLDC Motors ... - Atmel Corporation

AVR444: Sensorless control of 3-phase brushless DC motors

AVR448: Control of High Voltage 3-Phase BLDC Motor

AVR Motor Control.pdf

 

By the way, the driver chip you mentioned, in the datasheet it looks like it is only used for 2-phase motors, and you have a 3 phase motor. At least from what I gather, but I am not an expert. So there may be some configuration you could use that chip for to drive that motor, but I wouldn't know.

 

Thanks, that information will prove very useful..

But, its theory in majority do you have any info on Hardware circuits that would actually accomplish the task like back-emf-conditioning etc.