---In DynoMotion@yahoogroups.com, <tk@...> wrote:

I think a PWM prescale of 4 would give more like 12KHz. There is only one prescale for all the PWMs.

Yes you could toggle a bit every Time Slice to give a 2.7KHz square wave. Or check time using the Time_sec() function to toggle slower. 

Regards. 

TK

On Nov 23, 2013, at 9:58 AM, <eric@...> wrote:

 

I had a recent problem with the BOB that came with my mill going into fault mode.  I had figured out that the charge pump frequency was too high.  I scoped out the smooth stepper that I was replacing and found that a IO_PWMS_PRESCALE setting of 4 duplicated the SS frequency, (about 1Khz).

The problem I now have is the PWM for the brushless motor controller.  At the lower frequency, I can't take the duty cycle down low enough get to the full spindle speed of 6000.  Best I can get is around 3500.  Playing around, it looks like if I set the IO_PWMS_PRESCALE to 20, the charge pump appears happy, and I can get to 5500 RPM.
Is there more than one independently programmable PWM available?

If now, would another option be to tie the charge pump to an output and then create a simple forever loop toggling the charge pump line? Other than implementing a incrementing counter that reaches a certain value to signal when to toggle the line in order to slow down the frequency, is there a different option within the KFlop C world?

Eric

---In DynoMotion@yahoogroups.com, <tk@...> wrote:

Hi Eric,

I did think of another way. If all you need is a square wave for the charge pump.  Then you could use a Step/Dir Generator set to quadrature output mode. That would generate an accurate square wave anywhere from 0 to 500KHz.  Command an axis to Jog at 4X the desired frequency. 

Regards
TK

On Nov 23, 2013, at 7:01 PM, <eric@...> wrote:

 

I mistyped.  I did actually mean 12 Khz.  I just read some documentation that indicates the charge pump should be at 12.5 Khz.  Looks like I will need to make a small 555 timer circuit to run it. Can I power the timer circuit with one of the KFlop's outputs so it can continue to act as a watchdog?

Eric

---In DynoMotion@yahoogroups.com, <tk@...> wrote:

I think a PWM prescale of 4 would give more like 12KHz. There is only one prescale for all the PWMs.

Yes you could toggle a bit every Time Slice to give a 2.7KHz square wave. Or check time using the Time_sec() function to toggle slower. 

Regards. 

TK

On Nov 23, 2013, at 9:58 AM, <eric@...> wrote:

 

I had a recent problem with the BOB that came with my mill going into fault mode.  I had figured out that the charge pump frequency was too high.  I scoped out the smooth stepper that I was replacing and found that a IO_PWMS_PRESCALE setting of 4 duplicated the SS frequency, (about 1Khz).

The problem I now have is the PWM for the brushless motor controller.  At the lower frequency, I can't take the duty cycle down low enough get to the full spindle speed of 6000.  Best I can get is around 3500.  Playing around, it looks like if I set the IO_PWMS_PRESCALE to 20, the charge pump appears happy, and I can get to 5500 RPM.
Is there more than one independently programmable PWM available?

If now, would another option be to tie the charge pump to an output and then create a simple forever loop toggling the charge pump line? Other than implementing a incrementing counter that reaches a certain value to signal when to toggle the line in order to slow down the frequency, is there a different option within the KFlop C world?

Eric

---In DynoMotion@yahoogroups.com, <tk@...> wrote:

Hi Eric,

Like I said use quadrature output mode to get a square wave. See
http://dynomotion.com/Help/StepAndDirection/StepAndDir.htm

(Add 16 to the channel number. Use 24 for both TTL and Quadrature)
TK

On Nov 24, 2013, at 8:38 AM, <eric@...> wrote:

 

 Is there anyway to get closer to a 50% duty cycle from the Step/Direction generator?

As a quick test, I disconnected the X axis and used that output as a charge pump. 

Executing Jog(0, 12500); gave me a 12.5 KHz pulse, but the pulses are too short to satisfy the BOB.  I'm setup for steppers by the way.

Thanks,

Eric

---In DynoMotion@yahoogroups.com, <tk@...> wrote:

Hi Eric,

I did think of another way. If all you need is a square wave for the charge pump.  Then you could use a Step/Dir Generator set to quadrature output mode. That would generate an accurate square wave anywhere from 0 to 500KHz.  Command an axis to Jog at 4X the desired frequency. 

Regards
TK

On Nov 23, 2013, at 7:01 PM, <eric@...> wrote:

 

I mistyped.  I did actually mean 12 Khz.  I just read some documentation that indicates the charge pump should be at 12.5 Khz.  Looks like I will need to make a small 555 timer circuit to run it. Can I power the timer circuit with one of the KFlop's outputs so it can continue to act as a watchdog?

Eric

---In DynoMotion@yahoogroups.com, <tk@...> wrote:

I think a PWM prescale of 4 would give more like 12KHz. There is only one prescale for all the PWMs.

Yes you could toggle a bit every Time Slice to give a 2.7KHz square wave. Or check time using the Time_sec() function to toggle slower. 

Regards. 

TK

On Nov 23, 2013, at 9:58 AM, <eric@...> wrote:

 

I had a recent problem with the BOB that came with my mill going into fault mode.  I had figured out that the charge pump frequency was too high.  I scoped out the smooth stepper that I was replacing and found that a IO_PWMS_PRESCALE setting of 4 duplicated the SS frequency, (about 1Khz).

The problem I now have is the PWM for the brushless motor controller.  At the lower frequency, I can't take the duty cycle down low enough get to the full spindle speed of 6000.  Best I can get is around 3500.  Playing around, it looks like if I set the IO_PWMS_PRESCALE to 20, the charge pump appears happy, and I can get to 5500 RPM.
Is there more than one independently programmable PWM available?

If now, would another option be to tie the charge pump to an output and then create a simple forever loop toggling the charge pump line? Other than implementing a incrementing counter that reaches a certain value to signal when to toggle the line in order to slow down the frequency, is there a different option within the KFlop C world?

Eric