Looking for the cause of the apparent wild dither in the encoder output, something that would either have to have been carved into the disk if mechanical, and at the speed wobblies I'm getting, would absolutely have to be visible in the slot spacing I can see, it is that gross!
But I can see, when the feedback is enabled, wide variations in the pwm train in the halscope. Yes it should be some, but what I see with the spindle turning at 2 or 3 hundred rpms sure looks grossly huge to me. I'm reading up on the man page for pwmgen where it points out that with make-pulses being called at base-thread rate, 40 khz in this case, and pwm- freq at 1500, there would be a rather limited number of discrete values it could do, so the dither tries to average it to the wanted value average. As the C41 currently filtering the control output of the C41 interface has a 10uf filtering cap in the op-amp driving its output, its response isn't going to be a hugely step function anyway, it will ramp at whatever speed the lm327 op-amp can charge or discharge that 10 uf cap. So I've dropped the pwm-freq from 1500 to 500, which while seemingly slowing its response, also allows it to use a 3x more precise pulse width. But I see something else in the man page that is not adequately explained. If I turn it into a pdm generator by setting pwm-freq to 0, what then is its behavior? IOW, "since PDM is an inherently dithered process" would it be pulsing fast enough to be usable, particularly in keeping relay 1 in the C41 energized in between pulses. It strikes me I can check that easily on the Hal configuration page while its running, so I will. One of the things I did to the C41 was to change the 10uf cap that controls relay 1's timing out for a .1 cap as that speeds up the action of this relay since it is used in the NC mode as a substitute for the switch on the rear of the removed speed control, a switch that turns on when in the off position. Comments? Thanks. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> Where will it all end? Probably somewhere near where it all began. ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
