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« on: April 17, 2009, 03:10:12 PM »
even if this according to mach3 manual i can do through speed control chapter 4 page 4-12 pwm control as follow
3. PWM motor control
As an alternative to Step and Direction control, Mach3 will output a pulse width modulated
signal whose duty cycle is the percentage of full speed that you require. You could, for
example, convert the duty cycle of the signal to a voltage ( PWM signal on for 0% of time
gives 0 volts 50% gives 5 volts and 100% gives 10 volts) and use this to control an
induction motor with a variable frequency inverter drive. Alternatively the PWM signal
could be used to trigger a triac in a simple DC speed controller.
Figures 4.12 and 4.13
show the pulse width at
approximately 20% of
the cycle and 50% of the
cycle.
In order for the PWM
spindle speed signal to be
turned into direct current
(actually a direct voltage
is generally used as the input to variable speed drives, but you know what we mean) the
pulse signal it must transformed. In essence a circuit is used to find the average of the pulse
width modulated signal.
The circuit can be a
simple capacitor and
resistor or be much more
complex depending (a)
on how linear you want
the relationship between
the width and the final
output voltage and (b) on
the speed of response
you need to the changing pulse width.