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General Mach Discussion / Re: PWM vs Analog output for spindle control?
« on: November 23, 2020, 09:04:16 PM »Hi,QuoteMy question is:. If bypass the 0-10v converter, and feed the PWM signal directly to the 1200BWD driver and use PWM duty cycle to control the speed, would I get better linearity?
I doubt it, the non linearity is largely because the controller is actually a 'phase controlled rectifier bridge' and the transfer function ( the mathematical description
of the output verses the input) is highly non-linear with phase controlled bridges. It is in fact approximately linear to sin2 over a range of 0 to 90 degrees.
Is precise speed control that important? For years a and years we used manual mills and lathes which which not adjustable so had to accommodate whatever gear
ratio that was available.....so why the fixation on spindle speed now?
Craig
Thanks for the reply, that's the info I was looking for and approximately what I expected.
It's not so much a fixation with spindle speed, more a mild nagging curiosity. I get by fine with it as-is.
The reason I decided to explore it further, is because while reading the bldc driver manual, I realized the same terminals are used for both Analog and PWM inputs. Bypassing the Analog would be a simple matter of moving two wires on the breakout board and changing a setting in the bldc driver. I wouldn't have to do anything to the wiring harness.
Thanks for the response.