Which vfd is best for linux cnc?
08 Jun 2017 21:18 #94322
by devxpy
Replied by devxpy on topic Which vfd is best for linux cnc?
So do I have to buy a separate 5i25 FPGA card or the parallel port on my pc would be enough for using a 7i78 daughter card ?
(I only need 2 axes, so choosing 7i78 over a 7i76)
(I only need 2 axes, so choosing 7i78 over a 7i76)
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08 Jun 2017 22:50 #94323
by devxpy
Replied by devxpy on topic Which vfd is best for linux cnc?
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- Todd Zuercher
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09 Jun 2017 02:45 #94326
by Todd Zuercher
Replied by Todd Zuercher on topic Which vfd is best for linux cnc?
Yes, to use a 7i76 or 7i78, you have to have a Mesa FPGA card such as a 5i25. They will not work with an ordinary parallel port.
I don't know anything about the VFD you are looking at.
I don't know anything about the VFD you are looking at.
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09 Jun 2017 10:19 #94327
by devxpy
Replied by devxpy on topic Which vfd is best for linux cnc?
alright, i was thinking of just using a DAC to convert the pwm signal to analog 0-10v dc. gonna try that and see if it works this way..
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09 Jun 2017 10:42 #94328
by devxpy
Replied by devxpy on topic Which vfd is best for linux cnc?
you happen to know the max frequency of the linuxcnc pwm output?
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09 Jun 2017 13:05 #94337
by Todd Zuercher
Replied by Todd Zuercher on topic Which vfd is best for linux cnc?
The max frequency from a software PWM generator (parallel port) is going to depend on the computer and how fast it can run a stable basethread, and how good of a resolution you need. According to the docs "depending on CPU speed, etc, is capable of PWM frequencies from a few hundred Hertz at pretty good resolution, to perhaps 10KHz with limited resolution." (I think the 10KHz is rather over optimistic.) Basically the resolution will be the frequency period divided by the basethread period.
Hardware generated PWMs are a lot better, higher frequencies and a lot better resolution.
Hardware generated PWMs are a lot better, higher frequencies and a lot better resolution.
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09 Jun 2017 15:59 #94361
by andypugh
I would suggest using the PDM mode if you are using software PWM generation.
Replied by andypugh on topic Which vfd is best for linux cnc?
you happen to know the max frequency of the linuxcnc pwm output?
I would suggest using the PDM mode if you are using software PWM generation.
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