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Hi,
See these links.
AN INTRODUCTION TO SENSORLESS BRUSHLESS DC MOTOR
DRIVE APPLICATIONS WITH THE ST72141
http://www.st.com/stonline/books/pdf/docs/7209.pdf
Sensorless BLDC Control:
http://ww1.microchip.com/downloads/e...C%2000901a.pdf
Best regards,
Luciano
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Thanks for the info folks. Hmmm I'm wondering, why are Brushless DC motors called that when they clearly require AC to operate? I know that you would nearly always source that AC signal from a DC supply, but still it seems a bit strange.
Ah well.
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It looks like a bit of a PITA to setup a fully featured DC brushless controller... is there any way to shortcut this? Or is it going to be a whole chunk of work no matter what.
What's likely to happen if I just make up some sort of 'fixed' sequence to send to the motors which includes a startup routine? I know that if the motor got stopped, it may not start without assistance, but would the motor be likely to actually move properly? For now I just want to get it spinning, and it has a very low load on it, which is static, so once it's running there shouldn't be too many synch issues.
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Hi,
Brushless, sensorless motors with three connections are in
fact, not DC motors at all. They are actually permanent
magnet synchronous AC, 3-phase motors.
The commutation is done electronically. Three distinct
semi sinusoidal waveforms (not pure sinewave AC) that come in
at different times (or degrees) will causes the rotor to
rotate with the changing (alternating) magnetic fields of
the stator.
See page 7 of this PDF:
("some sort of 'fixed' sequence to send to the motor")
AN INTRODUCTION TO SENSORLESS BRUSHLESS DC MOTOR
DRIVE APPLICATIONS WITH THE ST72141
http://www.st.com/stonline/books/pdf/docs/7209.pdf
* * *
Read the documents below to understand the problem.
AVR444: Sensorless control of 3-phase brushless DC motors
http://www.atmel.com/dyn/resources/p...ts/doc8012.pdf
ATAVRMC100
http://www.atmel.com/dyn/resources/p...ts/doc7551.pdf
The ATAVRMC100 is an evaluation kit dedicated to brushless DC motor control, for
both Hall effect sensor control and sensorless control using Back ElectroMotive Force.
The kit includes an evaluation board, a 3-phase BLDC motor and a demonstration software.
It allows users to quickly evaluate the capability of the AVR® microcontroller
AT90PWM3 to control high speed brushless DC motor applications.
The kit can also serve as a development platform. Low cost AVR development tools
make debugging easier, and source codes, written in C, can be easily re-used by developers
for their own motor control applications.
* * *
Why do you need this motor?
What is the final application for this motor?
Best regards,
Luciano
Last edited by Luciano; - 12th January 2006 at 09:28.
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I can't actually say why I need it due to a NDA :P
It's for a prototype of something which needs a fast (3000rpm or higher) motor with a reliably constant speed. The motor will have almost no load, it just needs to spin fast, and constantly. For what I'm trying to do, a hard disk chassis is actually a good platform to build on, which is why a hard disk spindle motor seemed the obvious choice.
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Hi,
Why not use a ball bearing computer cooling fan with speed signal output?
(A PC cooling fan with tachometric signal output).
* * *
Fan Speed Control is Cool!
http://www.maxim-ic.com/appnotes.cfm...te_number/1784
If your PIC is too busy, use a I2C fan controller.
MAX6650 I2C fan controller
http://pdfserv.maxim-ic.com/en/ds/MAX6650-MAX6651.pdf
Best regards,
Luciano
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http://www.elektor-electronics.co.uk/
Magazine - Elektor Electronics February 2006
- Brushless Motor Controller
Best regards,
Luciano
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