On 09/29/2011 06:24 PM, Kirk Wallace wrote: > I'm trying to get my Shizuoka going after being idle during the Summer. > Some of the parts had "fallen" off. So, in putting it back together I > attended to an issue that bothered me from before. The SPI DAC I use to > feed the 0-10 V input to the spindle VFD wanders a bit and is enough to > notice the speed change at the spindle. I suspect the problem is that > the VFD and DAC have different supplies and grounds. I decided to try a > different approach and rigged up an opto-isolator which switches the 10V > speed supply to the 0-10V input. I feed the transmit side of the > opto-isolator with a PWM signal. I get much less wander, but after > adjusting the scale, I realized only the first 10% of the PWM range is > used to get 0 to 100% RPM (10V). I would like to have 100% pwm > correspond to 100% RPM or 10V input. I tried various resistors to limit > the input current or to pull the input down, but I still get the same > problem. > > Has anyone setup a PWM input to a VFD that utilizes the full PWM range? > If so, please let me know how it can be done. There is a 20mA input > also, but I don't know how it is supposed to work. I'll check the > manual, but hints would be appreciated. Otherwise, I my need to resort > to a digital potentiometer. Thanks for any help.
The PWM output (duty cycle) is 0 to 1.0. Is it possible you're telling it to go from 0 to 10, and by the time it reaches 10% of full scale it's already at 1.0? The 10 volts is only between the opto and the VFD input, nothing else needs to know about it. What about changing the scale. On ours (PWM driving a 0-10V output, which feeds the VFD's 0-10V input) we have the following in the ini file for a motor max speed of 2500 RPM. MAX_VELOCITY = 2500.0 OUTPUT_SCALE = 2500.0 OUTPUT_OFFSET = 0.0 MAX_OUTPUT = 2500.0 Karl ------------------------------------------------------------------------------ All of the data generated in your IT infrastructure is seriously valuable. Why? It contains a definitive record of application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-d2dcopy2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
