PWM signal on DAC (like Clipper's Option-11A)

[RomanSolonto]

Hi,

I have Turbo Pmac (not Clipper) and I need to control the output power of the laser.

 

I tried to use countdown timer to create PWM signal.

NCAutopilot creates this PLC:

 

OPEN PLC 9 CLEAR

I5112=1*8388608/I10

WHILE(I5112>0)

END WHILE

M525=M525-1

 

I make:

 

OPEN PLC 16 CLEAR

IF (P1011>0 AND P1012>0)

M4602=4095 //DAC ch#1 = max

M525 =P1011

WHILE (M525>0)

ENDWHILE

M4602=0 //DAC ch#1 = min

M525 = P1012

WHILE (M525>0)

ENDWHILE

ENDIF

 

where

m4602->Y:$78E08,0,12,U ; DAC ch#1

P1011 and P1012 - time for countdown timers

 

But I have some problems:

1. Frequency not stable

2. I think that it's not right way.

 

Is there any way to control frequency and duty cycle?

Is it possible to use PWM control of amplifiers for this?

[RomanSolonto]

Hi,

I have Turbo Pmac (not Clipper) and I need to control the output power of the laser.

 

I tried to use countdown timer to create PWM signal.

NCAutopilot creates this PLC:

 

OPEN PLC 9 CLEAR

I5112=1*8388608/I10

WHILE(I5112>0)

END WHILE

M525=M525-1

 

I make:

 

OPEN PLC 16 CLEAR

IF (P1011>0 AND P1012>0)

M4602=4095 //DAC ch#1 = max

M525 =P1011

WHILE (M525>0)

ENDWHILE

M4602=0 //DAC ch#1 = min

M525 = P1012

WHILE (M525>0)

ENDWHILE

ENDIF

 

where

m4602->Y:$78E08,0,12,U ; DAC ch#1

P1011 and P1012 - time for countdown timers

 

But I have some problems:

1. Frequency not stable

2. I think that it's not right way.

 

Is there any way to control frequency and duty cycle?

Is it possible to use PWM control of amplifiers for this?

[Gregs]

You might try combining PLC 9 and 16 into PLC 0, and perhaps reducing I8:

 

Open PLC 0 Clear

IF (P1011>0 AND P1012>0)

M4602=4095 //DAC ch#1 = max

M525 =P1011

WHILE (M525>0)

I5112=1*8388608/I10

WHILE(I5112>0)

END WHILE

M525=M525-1

ENDWHILE

M4602=0 //DAC ch#1 = min

M525 = P1012

WHILE (M525>0)

I5112=1*8388608/I10

WHILE(I5112>0)

END WHILE

M525=M525-1

ENDWHILE

ENDIF

Close

 

Also, is 1ms enough resolution? I5112=1*8388608/I10 could be reduced (e.g. I5112=0.5*8388608/I10).

 

If this is a Turbo PMAC2, there is probably a better way which uses position compare pulse modulated output. I attached a document describing how to do this.

[Gregs]

You might try combining PLC 9 and 16 into PLC 0, and perhaps reducing I8:

 

Open PLC 0 Clear

IF (P1011>0 AND P1012>0)

M4602=4095 //DAC ch#1 = max

M525 =P1011

WHILE (M525>0)

I5112=1*8388608/I10

WHILE(I5112>0)

END WHILE

M525=M525-1

ENDWHILE

M4602=0 //DAC ch#1 = min

M525 = P1012

WHILE (M525>0)

I5112=1*8388608/I10

WHILE(I5112>0)

END WHILE

M525=M525-1

ENDWHILE

ENDIF

Close

 

Also, is 1ms enough resolution? I5112=1*8388608/I10 could be reduced (e.g. I5112=0.5*8388608/I10).

 

If this is a Turbo PMAC2, there is probably a better way which uses position compare pulse modulated output. I attached a document describing how to do this.

Position-Compare Pulse-Modulated Output (2).doc