At one time in the darks mists of history, EMC(1?) had an axis brake output for exactly this function - it would turn the brake on and off based on g-code commands. I'm not sure if it made it into EMC2 and thus LinuxCNC. If I wasn't lazy I would check the manual and see if the "motion" component has a brake pin.
On Sun, Jun 9, 2013, at 01:34 PM, Andrew wrote: > 2013/6/9 Florian Rist > <[email protected]<https://mail.google.com/mail/u/0/?view=cm&fs=1&tf=1&[email protected]> > > > > > Hi Andrew > > > > Hi Florian, > > > > > It depends on when you need the brakes on. > > > > Well, the brakes are supposed to prevent the servo from moving when > > powered off, for safety reasons but also to be able to power up the > > machine without the need to home the axis (nor sure if this is really > > possible) > > > The simple solution is connect brakes to enable. > > > > > So I take the enable signal for the servo controller (7i39) and use that > > to switch on the brae supply, right? > > > > I guess so. I usually use relay modules like this > http://www.ebay.com/itm/251267628031 for that purpose. > > > > > > Other is powering brakes when commanded velocity magnitude > > > exceeds some near-zero value. > > > > sounds more elegant, but that means I have to use an extra i/o pin (no > > problem there are plenty of them free) and generate the signal for it > > (don't know how to do so, right now) > > > > Yes. I would use abs to get absolute value of velocity and then comp to > compare it to say 0.1 or 0.01 (slow enough but not zero). > http://www.linuxcnc.org/docs/html/man/man9/abs.9.html > http://www.linuxcnc.org/docs/html/man/man9/comp.9.html > The question is which signal to use for velocity input: > axis.N.joint-vel-cmd (or probably PID outputs) for each axis with 3 > independent brakes, or motion.current-vel for common brake signal. > Something like this. We can continue with details if nesessary. > > Andrew > ------------------------------------------------------------------------------ > How ServiceNow helps IT people transform IT departments: > 1. A cloud service to automate IT design, transition and operations > 2. Dashboards that offer high-level views of enterprise services > 3. A single system of record for all IT processes > http://p.sf.net/sfu/servicenow-d2d-j > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users -- John Kasunich [email protected] ------------------------------------------------------------------------------ How ServiceNow helps IT people transform IT departments: 1. A cloud service to automate IT design, transition and operations 2. Dashboards that offer high-level views of enterprise services 3. A single system of record for all IT processes http://p.sf.net/sfu/servicenow-d2d-j _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
