On Monday 01 March 2021 14:11:00 Jon Elson wrote: > On 03/01/2021 11:02 AM, Feral Engineer wrote: > > Hi Jon > > > > No encoders. Besides the 7i76e and raspberry pi, the machine is > > using the original steppers and electronics. > > OK, without encoders, then you are limited by the servo > period. So, figure some way to tie > the sensor in with the mechanical switch, and make the home > move slow enough so you are doing less than 1000 > steps/second. Previous messages mentioned some schemes to > tie the sensor in with the switch. The idea is that > LinuxCNC will make a fast approach until the and of the > sensor and switch show true at HOME_SEARCH_VEL, then back > off and approach slowly until they show true again at > HOME_LATCH_VEL, and that is the home position. > > Jon This gives me an idea Jon, but would assume the back off move runs the backoff move until the switch opens again.
The problem with homing the bs-1 is that the home switch is activated by a notch in the hub of its spindle and is only good for about 2 degrees, so if I use a SEARCH_VEL fast enough to find home in a reasonable time, by the time the home logic recognizes the switch, it will coast on by it, look again, find the switch false and will then run it at search vel for another full turn. Wash, rinse, and repeat forever. So I have to use a search vel that's very slow. Much slower than it can move. So, if I start a timer whose job is to lengthen the switches closure, holding that state true for 3 or 4 seconds, however long enough to back it off far enough to bypass the switch going the other way, then set HOME_LATCH_VEL slow and the same polarity as HOME_SEARCH_VEL, it should then find it again, and do it w/o any offsets if HOME_LATCH_VEL is slow enough. There is a small offset now, perhaps .005 to .01 degrees. This is complicated by there don't seem to be a MAX_OUTPUT setting that stops the windup in the PID, and if I don't use very slow ACELL settings, it tries to reverse too quick, which crowbars the 400 watt 24 volt psu, shutting it off for a minute plus to cool and needs a power cycle to restore. The F2 power cycle caused by the resulting following error unhomes the whole machine, so wash, rinse, and repeat forever. Frustrating is not an adequate description. Or will stretching the switch with a timer screw things up as the 4 something degree HOME_OFFSET move takes place with the possibility the timer hasn't timed out by the time the HOME_OFFSET move is completed? IDK. Advice plz. Thanks Jon. > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
