PWM feedback?
14 May 2017 20:19 #93197
by caio
Replied by caio on topic PWM feedback?
@tommylight
yes, i get a clean square wave 50% dc
@PCW
thanks, i'll try to improve the pid.
i'm also not sure about maxoutput (pid and encoder), i set it up 24000, as the max spindle rpms, is that right?
yes, i get a clean square wave 50% dc
@PCW
thanks, i'll try to improve the pid.
i'm also not sure about maxoutput (pid and encoder), i set it up 24000, as the max spindle rpms, is that right?
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20 May 2017 21:00 #93408
by andypugh
Reading PWM is only really possible with hardware timers, something that can accurately measure the pulse width.
LinuxCNC HAL could only poll the input, so the best time-stamp resolution that you could expect would be same as the thread rate, either 1mS or 50µS if you run a base thread.
This that to get a value with useful resolution from measuring the PWM you would need to run a very slow PWM rate.
(example: 5rpm resolution and 5000rpm required using the base thread at 50µS would be a 20Hz PWM.)
Replied by andypugh on topic PWM feedback?
Sounds strange linuxcnc can't read pwm.
Reading PWM is only really possible with hardware timers, something that can accurately measure the pulse width.
LinuxCNC HAL could only poll the input, so the best time-stamp resolution that you could expect would be same as the thread rate, either 1mS or 50µS if you run a base thread.
This that to get a value with useful resolution from measuring the PWM you would need to run a very slow PWM rate.
(example: 5rpm resolution and 5000rpm required using the base thread at 50µS would be a 20Hz PWM.)
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