Generating 3-phase sine wave..

skimask · - 16th July 2008, 16:39

More information than you can shake a stick at here...doesn't delve too much into the 3 phase aspect though...
http://www.picbasic.co.uk/forum/show...light=inverter

**Luciano** · - 17th July 2008, 08:59

Hi Sylvio,

(Somehow related).

Speed Control of 3-Phase Induction Motor Using PIC18 Microcontrollers

Microchip AN843: (PDF)
http://ww1.microchip.com/downloads/e...tes/00843a.pdf

(Code and PDF).
http://www.microchip.com/stellent/id...pnote=en012011

Example of 3-phase bridge driver chip:
http://www.irf.com/product-info/data...ata/ir2136.pdf

Best regards,

Luciano

**sirvo** · - 18th July 2008, 20:33

Well.. Thank you Skimask and Luciano. Excelent readings!

So, I've bought a 16F777 and it has 3 CCP modules. As suggest in the readings above, it becomes easier to create an analog output when using high PWM frequencys. Using @ 20Mhz and Mister_E's PicMultiCalc, it turn out that it can generate frequencys > 20Khz, what is enought to this application.

Timer2 is responsable to control the PWM frequencys (all the same).

Timer1 is responsable to create the interruption to supply the new duty cycle value.

Now, let'ss think about the sine table and the software. Just to remember, I'll create an interface to control sine frequency, amplitude and also the sine table, as it would be interesting to create harmonics, sags and swells.

The sine table could be in the pic's data memory or it could be sent throught USART everytime that the user changes the interface option, like frequency. Do you think that it would work in real time using USART?

Thanks again!

**sirvo** · - 25th July 2008, 21:29

Well, things have been working until now...

When Timer1 interrupts, a INDEX var is summed and another position in a sine table is selected.. then a new value is output throught HPWM.

The sine table is filled with 72 number.. So, to create a 60Hz sine wave, o must read it at approx. 4.32KHz.

So, When I set timer1 to 64386 (1:1 prescaler @ 20MHz), it should interrupt at ~4.32KHz and create de 60Hz sine wave... but, it is generating a 26Hz... if I set timer1 to 65000, it decreases the 26Hz to 20Hz ... I didnt get iT! It should read the table faster, shoul'nt it?

Well, thanks!!!

skimask · - 25th July 2008, 21:48

Originally Posted by sirvo

So, When I set timer1 to 64386 (1:1 prescaler @ 20MHz), it should interrupt at ~4.32KHz and create de 60Hz sine wave... but, it is generating a 26Hz... if I set timer1 to 65000, it decreases the 26Hz to 20Hz ... I didnt get iT! It should read the table faster, shoul'nt it?

I'm guessing here, wild stab, since I don't see any other code here...
It might be reading it faster, but it might be missing/skipping a Tmr1 interrupt due to how long it takes to accomplish your interrupt code.
Try increasing the number by small amounts, see if it actually increases up to a point, and then drops off.

**sirvo** · - 25th July 2008, 21:57

So, here we go..

Didnt show var byte stuffs..

Code:

define  OSC 20

DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_SPBRG 10  ' 115200 Baud @ 20MHz, -1,36%
DEFINE HSER_CLROERR 1 ' Clear overflow automatically

' Set CCPx pins to outputs
TRISC.2 = 0 ' CCP1 output
TRISC.1 = 0 ' CCP2 output (could also be assigned to RB3)
TRISB.5 = 0 ' CCP3 output

' Set CCP modules to PWM mode
CCP1CON = %00001100 ' Mode select = PWM
CCP2CON = %00001100 ' Mode select = PWM
CCP3CON = %00001100 ' Mode select = PWM

INTCON = %11000000
LOAD = 64386' 4320Hz
'LOAD = 0
TMR1H = LOAD.HIGHBYTE
TMR1L = LOAD.LOWBYTE
T1CON = %00000001
PIE1.0 = 1
PR2 = 49
PORTD.0 = 0
' Set TMR2 up for 1:1 prescale & turn it on
T2CON = %00000100 ' TMR2 ON 1:1 prescale


ASM
INT_LIST macro ;IntSource, Label,    Type, ResetFlag?
    INT_Handler TMR1_INT, _Timer1,   PBP, yes 

    endm
    INT_CREATE ; Creates the interrupt processor
ENDASM
@    INT_ENABLE  TMR1_INT   ; Habilita interrupção do TMR1 



MAIN: 
    IF FLAG = 1 THEN  
        flag = 0 
        CONTA = CONTA + 1
        CONTB = CONTB + 1
        CONTC = CONTC + 1
        if contA = 71 then contA = 0
        if contB = 71 then contB = 0
        if contC = 71 then contC = 0
            
        index  = conta
        GOSUB tabela
        va = v
        
        index  = contB
        GOSUB tabela
        vb = v
        
        index  = contC
        GOSUB tabela
        vc = v
        
        GOSUB SAIDA
    endif      
    GOTO MAIN

    
TABELA:
    SELECT CASE DIST
    CASE 1: ' Fundamental
           LOOKUP INDEX, [100,109,118,126,135,143,151,158,165,171,177,183,187,191,195,197,199,200,200,199,198,196,193,189,185,180,175,168,162,154,147,139,130,122,113,104,96,87,78,70,61,53,46,38,32,25,20,15,11,7,4,2,1,0,0,1,3,5,9,13,17,23,29,35,42,49,57,65,74,82,91], V 
    CASE 2: ' 3 com 20%
           LOOKUP INDEX, [100,114,127,140,152,162,170,177,182,185,187,187,187,185,184,182,181,180,180,180,181,182,184,185,187,187,187,185,182,177,170,162,152,140,127,114,100,86,73,60,48,38,30,23,18,15,13,13,13,15,16,18,19,20,20,20,19,18,16,15,13,13,13,15,18,23,30,38,48,60,73,86], v
    CASE 3: ' 3 com 20% + 5 com 10%
           LOOKUP INDEX, [100,118,135,150,161,170,175,178,178,178,177,177,178,180,182,185,188,189,190,189,188,185,182,180,178,177,177,178,178,178,175,170,161,150,135,118,100,82,65,50,39,30,25,22,22,22,23,23,22,20,18,15,12,11,10,11,12,15,18,20,22,23,23,22,22,22,25,30,39,50,65,82], V
    CASE 4: ' 3 com 20% + 5 com 10% + 7 com 10%
           LOOKUP INDEX, [100,124,144,159,168,171,170,168,168,171,175,181,187,190,190,188,184,181,180,181,184,188,190,190,187,181,175,171,168,168,170,171,168,159,144,124,100,76,56,41,32,29,30,32,32,29,25,19,13,10,10,12,16,19,20,19,16,12,10,10,13,19,25,29,32,32,30,29,32,41,56,76], V
    CASE 5: ' 5 com 10% + 7 com 20%
           lookup index, [100,122,139,149,151,147,141,136,137,145,157,172,186,194,197,194,188,183,181,183,188,194,197,194,186,172,157,145,137,136,141,147,151,149,139,122,100,78,61,51,49,53,60,64,63,55,43,28,14,6,3,6,12,17,19,17,12,6,3,6,14,28,43,55,63,64,59,53,49,51,61,78], v
    CASE 6:
           return
    CASE 7:
           return 
    end select
return

SAIDA:
        CCP1CON.4 = VA.0
        CCP1CON.5 = VA.1
        CCPR1L = VA >> 2
        CCP2CON.4 = VB.0
        CCP2CON.5 = VB.1
        CCPR2L = VB >> 2
        CCP3CON.4 = VC.0
        CCP3CON.5 = VC.1            
        CCPR3L = VC >> 2
RETURN
  
Timer1:
    TMR1H = load.highbyte 
    TMR1L = load.lowbyte                
    FLAG = 1 
@ INT_RETURN  

END

skimask · - 25th July 2008, 22:07

Do(does?) DT_INT's reset TMR1IF for you?

Past that, get rid of everything else and just toggle a pin, only toggle a pin, and nothing but toggle a pin...and measure that and see what happens.

skimask · - 26th July 2008, 20:09

What does this do on PortD.0?

Code:

define  OSC 20
DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_SPBRG 10  ' 115200 Baud @ 20MHz, -1,36%
DEFINE HSER_CLROERR 1 ' Clear overflow automatically
TRISC.2=0 : TRISC.1=0 : TRISB.5=0 : TRISD.0 = 0 : CCP1CON=12 : CCP2CON=12
CCP3CON=12 : INTCON=$c0 : LOAD=64386 : TMR1H=LOAD.HIGHBYTE
TMR1L=LOAD.LOWBYTE : T1CON=1 : PIE1.0 = 1 : PR2 = 49 : PORTD.0 = 0 : T2CON = 4
ASM
INT_LIST macro ;IntSource, Label,    Type, ResetFlag?
    INT_Handler TMR1_INT, _Timer1,   PBP, yes 
    endm
    INT_CREATE ; Creates the interrupt processor
ENDASM
@    INT_ENABLE  TMR1_INT   ; Habilita interrupção do TMR1 
MAIN: GOTO MAIN
Timer1: TMR1H = load.highbyte : TMR1L = load.lowbyte
     if portd.0 = 0 then
          portd.0 = 1
     else
          portd.0 = 0
     endif
@ INT_RETURN  
END

My point is that it looks like your program 'flow' is jacked up and needs to be reworked.

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