Spindle Speed to Serial Port
19 Jul 2010 17:16 #3420
by gangsta
Replied by gangsta on topic Re:Spindle Speed to Serial Port
Thanks for the replys
Andy, thats what I was hoping to hear, I asked a few times yesterday in the IRC to see if I could just do PWM > low pass. How can I find out if my VFD terminals are at mains potential?
Also will a single stage filter work ok, or would a 2 stage filter be better?
ZIG, thanks for the suggestions. I have 3 LPT ports in my system. So I may play more with HAL in the future. I would in the future still like to get the spindle speed command passed out to a PIC, so that I dont need to rely on the computer generating PWM. Using an external board it can be closed loop without tying up the processor. For now an isolated low pass it is
Andy, thats what I was hoping to hear, I asked a few times yesterday in the IRC to see if I could just do PWM > low pass. How can I find out if my VFD terminals are at mains potential?
Also will a single stage filter work ok, or would a 2 stage filter be better?
ZIG, thanks for the suggestions. I have 3 LPT ports in my system. So I may play more with HAL in the future. I would in the future still like to get the spindle speed command passed out to a PIC, so that I dont need to rely on the computer generating PWM. Using an external board it can be closed loop without tying up the processor. For now an isolated low pass it is
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19 Jul 2010 18:40 #3421
by andypugh
Replied by andypugh on topic Re:Spindle Speed to Serial Port
gangsta wrote:
In fact, you could use that potentiometer +10V as your 10V for the pwm converter.
Here is my schematic. If I was doing it again I would use the +10V from the VFD instead of the DC-DC convertor. I would also probably skip the constant current source. Note that there are two PWM to voltage convertors on this schematic, plus some relay logic to steer them to the right places. In fact, you can probably ignore all of the schematic other than the "yes, it is perfectly do-able" aspect.
picasaweb.google.com/lh/photo/QYTcQg-xDq...ymTQ?feat=directlink
I know, I saw both questions, somewhat after you had logged off again.Andy, thats what I was hoping to hear, I asked a few times yesterday in the IRC to see if I could just do PWM > low pass.
They won't be, this was a peculiar drive intended to be driven from an on-board pot. But to be sure, just check it with a multimeter. Don't worry too much about the "input" terminal, but you will almost certainly find that all the low-sides are common and the +10V for a pot is only +10v.How can I find out if my VFD terminals are at mains potential?
In fact, you could use that potentiometer +10V as your 10V for the pwm converter.
Single stage is fine, you will probably want a time constant around 20Hz (nothing higher makes any real sense with a 50Hz motor) and a 1kHz PWM, so the sharpness of the cutoff is irrelevant.Also will a single stage filter work ok, or would a 2 stage filter be better?
You worry too much. (Or have spent too long on PICs) Running a PID in the servo thread takes almost no CPU.Using an external board it can be closed loop without tying up the processor. For now an isolated low pass it is
Here is my schematic. If I was doing it again I would use the +10V from the VFD instead of the DC-DC convertor. I would also probably skip the constant current source. Note that there are two PWM to voltage convertors on this schematic, plus some relay logic to steer them to the right places. In fact, you can probably ignore all of the schematic other than the "yes, it is perfectly do-able" aspect.
picasaweb.google.com/lh/photo/QYTcQg-xDq...ymTQ?feat=directlink
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