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Mach4 General Discussion / Help with maths on variables in PMC - Feedback from VFD
« on: January 09, 2021, 09:07:47 PM »
I have set up Modbus comms between my Powerflex VFD and Mach4 and I am able to control the spindle, read status logic bits, etc, but I was hoping to get the output frequency from the drive and display it as an RPM DRO on my screen. To control the speed on my spindle via PMC, I am taking the Core Val 'Spindle RPM', putting it into a variable and dividing by 6 to get the required Hertz. Then writing that variable to the VFD register.
When I attempt to do the reverse with the VFD Hertz output register, I can move the register value with a Read Reg instruction and the variable shows the correct value in the bottom section of the PMC editor. But if I try to multiply the value by 6 at the end of the rung, I get the following message
"Variable 'VFDRpm' not assigned to, e.g. MOV statement, and ADD statement, etc. This is probably a programming error; now it will always be zero."
When I attempt to do the reverse with the VFD Hertz output register, I can move the register value with a Read Reg instruction and the variable shows the correct value in the bottom section of the PMC editor. But if I try to multiply the value by 6 at the end of the rung, I get the following message
"Variable 'VFDRpm' not assigned to, e.g. MOV statement, and ADD statement, etc. This is probably a programming error; now it will always be zero."