Two phases and a neutral on 16F1936

[nailuy]

I want to make PWM for electric engine.
Truth table for phases and neutral positions are:
#1 F1=1, F2=0, N=0
#2 F1=1, F2=1, N=0
#3 F1=0, F2=1, N=0
#4 F1=0, F2=1, N=1
#5 F1=0, F2=0, N=1
#6 F1=1, F2=0, N=1
#7 F1=1, F2=0, N=0
#8 F1=1, F2=1, N=0
#9 .... and so on
My question is how to make a precise delay between CCP1 and CCP2 (F1, F2).
How can I make link between "N" to CCP1 and CCP2.
Thnks.

[Ttelmah]

Realistically, this is not two phases and neutral, but standard 3 phase BLDC control. The 'neutral', is a virtual point inside the motor, where the 3 phases meet.
Have a look at AN857a from MicroChip, which shows doing this in software using a timer to control the PWM, and phase timing. I have done this with CCS, without problems. AN970, shows a more sophisticated control using a PIC18 (downside of the AN857 version comes when loads change rapidly, or supply voltages change a long way).
It is actually a lot easier to do using an IC designed to do it. Unless you have some special 'extra' requirement. Toshiba in particular do a couple of chips that make this a 'doddle'.

Best Wishes

[nailuy]

Thank you for reply.
I want to learn how to work with PWM between CCP1 and CCP2 (delay's).
I have other "doddle" to solve, and are already solved if I use this PIC16F.
I'm not using PWM on "N" because I'm not need it.
Only two question's, how can I work with two CCP delayed and how can I make this N to be correlated ?
If I work with 3 phases I make inside of engine neutral, but I need only outside, I have only 2 coils.. at 90 degree.
I'm not understanding language of Mplab.
Thank you.

[Ttelmah]

The PWM's can be set to use two different timers.
Start one timer.
Delay for the offset time required
Start the second timer.
Program the two PWM's.

You then have two PWM's with the time delay between them.

However normally you'd have PWM, common between the phases, used to control the power, and modulate the drive phases at a much lower frequency. Typically perhaps PWM at 10KHz+, with phase modulation much slower than this. For instance, a 12phase motor at 8000RPM, still only wants 1600Hz on the phase changes.

You are going to run into problems controlling your third phase, because of the latency involved in code. Even 1uSec of delay in turning off a drive combination, is too long, if you are already turning on the other bits....

This is why operating all the bits in sync is needed.

Best Wishes

[asmboy]

You should understand that the PIC by itself is not always the best way to get your task done. Using specialized function chips for time critical functions is important, especially for you project, where small amounts of time indeterminacy can be problematic.

As somebody who has BTDTGTTS with multiphase motors, several times, - the KEY wisdom Ttelmah was kind enough to share with you is this:

[nailuy]

I find this topic and is much closer to what I need.
http://www.ccsinfo.com/forum/viewtopic.php?t=37807&start=3
but is based on the interruption.
I will continue to search how to make delay between timers like you say

[Ttelmah]

I too have built several BLDC controllers, including one based directly on AN857, which is why I'll repeat the comment reinforced by asmboy, of just how much easier this is using an IC designed to do it....

On the delayed PWM's:

[Ttelmah]

I think it is also important to get the poster to understand that the PWM frequency, is not normally the phase frequency.

Have a look at:
<http://www.youtube.com/watch?v=Jdhgi5_kmvk>

Which shows the waveforms involved. The PWM, is being modulated to control the power, while the phase pulses change at a much slower frequency to give the motor speed required.

Best Wishes

[nailuy]

yes Ttelmah this I need it.
Thank you.
Table of truth was wrong sorry.
#1 F1=1, F2=na, N=0
#2 F1=1, F2=1, N=0
#3 F1=na, F2=1, N=0
#4 F1=0, F2=na, N=1
#5 F1=0, F2=0, N=1
#6 F1=na, F2=0, N=1
#7 F1=1, F2=na, N=0
#8 F1=1, F2=1, N=0
#9 .... and so on
na is value between 0-1 (if it is 0 or 1 I have brake.)
on the old table should be operated with a fill of 50% and a difference of 60 degrees
Now with the new table I must make a filling of 33% and a difference of 90 degrees.
How can I change this PWM filling?
for degree now I understand.
Thnks.

[nailuy]

I found it:

int16 DUR;

DUR = 408; // [408/(4*(200+1))]=0.5=50%

set_pwm1_duty(DUR);
Thank you guys.