(Added [PIC] tag as well)

I think you should start with open loop and then when it locks to the
position sensors (aka. measuring the desired rev) you can then switch
to closed loop mode. I am not sure if you should start at a high PWM,
I would rather try to rotate the magnetic field at a constant speed
and gradually increase the power till it locks. Maybe it can learn by
itself if the estimated load is constant at the startup? I mean that
the next time it tries to start at a closer value to the one it locked
last time.

Tamas



---------- Forwarded message ----------
From: Halil G=FCr <gurhalil@gmail.com>
Date: Mon, Feb 1, 2010 at 11:05 PM
Subject: brushless motor doesnt start without hand
To: piclist@mit.edu


I have developed an application that drives a sensored brushless dc motor
with a pic24f,
what my problem is that sometimes the motor doesnt start. i had to give the
motor a start by hand... after the start everything works fine. im checking
the pwm signals for corresponding HallEffect, the pwm is there but motor
doesnt starts well. i did some research and assigned a high duty cycle at
start(almost 90%) then decrease it slowly but no change,
Does anybody know what is wrong or special with the start-up? how can i make
the motor start?

--
Halil G=DCR
--
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-- =

/* www.mcuhobby.com */ int main() { char *a,*s,*q; printf(s=3D"/*
www.mcuhobby.com */ int main() { char *a,*s,*q; printf(s=3D%s%s%s,
q=3D%s%s%s%s,s,q,q,a=3D%s%s%s%s,q,q,q,a,a,q); }",
q=3D"\"",s,q,q,a=3D"\\",q,q,q,a,a,q); }

-- =

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