On Fri, 2010-12-17 at 22:02 -0700, Cathrine Hribar wrote: > > Hi Kirk: > > Have given your suggestion of tuning up the setup I have and will proceed > toward that end. > > I was wondering if u could tell me what this means: Setting PFD, "Adjustable, > percent fast decay". The manual I got with my stepmaster stepper board says > this should be adjusted for each axis. It doesn't say what it does or how it > affects the operation of the stepping motors. Do u know what this is and how > it would help me tweak the system? > > Thanks for ur time; > > Bill
The Allegro manual may shed more light on it: http://www.allegromicro.com/en/Products/Part_Numbers/3977/3977.pdf I don't have a lot of experience with steppers, my mill was a working system from the factory, so it "just works". I have been playing with a small stepper and an L298 driver, and had some success but I haven't come up with a tuning strategy. Your step/dir driver is more complex. It is a micro stepping driver, so the number of sub-steps per normal step is selectable. The decay setting seems to allow the drivers to behave differently for different sub-steps. I haven't read through the datasheet, but it didn't look too terribly obvious. This link seems to have some information: http://www.piclist.com/techref/io/stepper/hipwrbp-gm.htm Bipolar steppers are driven by h-bridges. The H refers to the normal schematic representation of this kind of circuit. The driver is an array of four transistors or, more simply, switches. The direction of current through a stepper coil is controlled by turning on the top right, top left, bottom left and bottom right switches so that the current goes forward or in reverse. There are two coils, so there are two h-bridges to control one motor. http://en.wikipedia.org/wiki/H-bridge With the details being pretty complex, it may be best if someone with experience chimes in with a rule of thumb on how to select a proper decay setting. It may be that the setting will only make a few percent difference. From what little I've read, it may affect the noise and efficiency at certain step rates, or help slightly with slipping at intermediate step rates, but this is a guess. If this is the case, it may be that just trying different settings and keeping the ones that help may be the way to go. What is the voltage of the motor power supply? The datasheet says the driver is rated for 37 Volts, so it would be nice to have the supply voltage close to that. The power supply should have a large capacitor, or a pair of them. They shouldn't bulge a all, If they do, they may be on their way out. Posting pictures of your set up would help. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ Lotusphere 2011 Register now for Lotusphere 2011 and learn how to connect the dots, take your collaborative environment to the next level, and enter the era of Social Business. http://p.sf.net/sfu/lotusphere-d2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
