Single phase motor brushless controller

[nawait1]

Hi,

I have to make a controller for a single phase brushless motor with permanent magnets (2 poles) with an Hall effect sensor. The rotation speed of the motor has to be modified according to the information provide by a sensor.

Motor :

http://www.hebergementimages.com/images/1216606047_brushless.JPG

Does this circuit OK to control the motor ? :

http://www.hebergementimages.com/images/1216607743_Dessin1.jpg


The effect Hall sensor detects the transition between the nort pole and the south pole. When the transition is detected the current in the coil is reversed. The PIC will emit logical signal 0 and 1 to drive the 4 Mosfet. I think that a Mosfet driver will be suitable between the PIC and the Mosfet. What kind of components i can use ? (PIC,Mosfet driver, Mosfet)

- Input 12~24Volt, operating voltage 16.8Volt
- Rotating speed 6000~12000rpm
- Output power 10~20watt

Thanks in advance for your help.

[SteveM732]

You should have continued this discussion in your other thread (http://www.rcgroups.com/forums/showthread.php?t=882210) that asks this same question.

[nawait1]

I would prefere to continue on this thread because informations are not sufficient on the other one, this one is more comprehensive.

Thanks

[SteveM732]

Alrighty then.

I think you want to make Q3 and Q4 N-channel FETs.

Any thoughts yet on how to ensure rotation in the proper direction?

[Peter Seddon]

Will you be able to generate enough torque to usefully drive a load with this set up? Most motors use a rotating three phase field to drag the rotor around. I think I can see conditions which depending on the load the motor may not commutate properly and just flip back to the start position.

regards Peter

[david_dewit]

Look at the Allegro A1442 Motor driver IC

You will find some usefull info here:

http://www.rcgroups.com/forums/showthread.php?t=596219

The IC will run motors below 400mA, you will need a h-bridge to run larger motors. Starts very reliably in same direction every time. IC is run off std brushed esc or pic.

Hope this is of some use to you.

Dave

[nawait1]

Thank you for your replies.

I think i will use N-channel FETs for the 4 Mosfet because the efficiency is better than P-channet FETs. For the rotation in the proper direction, the stator is shaped eccentrically :

http://www.hebergementimages.com/images/1216691485_assymetrique.JPG

I think that with this structure, the motor can start in the right direction.
Thank you david_dewit, your link is very interesting.

[nawait1]

I am done this circuit :

http://www.hebergementimages.com/images/1218089778_controller.JPG


What do you think about that ? Can that work?

Thanks

[SteveM732]

Having U12 and U5 doesn't make much sense to me unless you already have some of them on hand. I'd just spec out one regulator that could handle the whole load.

You might have problems with your 20 volt VDS limit on D1 and D3 (diodes are "D" a mosfet should be "Q" or "M"). If your battery pack is less than 20 volts you will be ok and if less than 25 volts you might be ok but I wouldn't put any money on it.

You also must be careful with U3 and U4 since there is no hardware mechanism to prevent enabling all 4 outputs simultaneously. One little think-o in firmware and your H-bridge will leak its magic smoke.