andy pugh wrote: > On 1 May 2012 12:26, cogoman <cogo...@optimum.net> wrote: > >> I don't see how they could switch from 1/10 to full step without letting >> LinuxCNC know, and having LinuxCNC reduce the number of steps being >> sent, unless they used a clock multiplier, which would make it look like >> full step to the control, >> > > I imagine it is an internal clock-divider, so at high speed it > full-steps every N input pulses, and at low speed it microsteps every > input pulse. > I've always been very suspicious of this claim (that Geckos switch from microstepping to full steps at some speed). it seems totally unnecessary, and might be hard to do without causing some manner of glitch. What I think really happens is that at some speed the sinusoidal current command gets enough ahead of the motor's inductance that the winding current never reaches the current setpoint, and so the transistors naturally switch from chopping mode to regulate current to a mode where they are on for the half electrical cycle of that winding. I expect every microstepping chopper drive will do the same.
In other words, the drive does this naturally due to the lag of the motor's inductance, and there is no special circuit at all to perform this function. And, the speed at which this happens is determined by the DC supply voltage and the motor inductance. Jon ------------------------------------------------------------------------------ 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
