Jon,
It doesn't "switch" from 1/10 to full-step, it "morphs". It's not done with clocks and dividers, its done more in the analog side. That's the difference that Mariss adds. Anyone can built a microstepping drive. There are scores of application notes and open source designs. To do what Geckodrive does requires a bit of lateral thinking, and not just copy what is all ready out there. As to the advantage of fullstepping over micro-stepping, a full stepping gtive will provide more torque at higher speed. The reason that you run steppers at a voltage of up to 20 times the plated voltage is to get rapid current changes in the coils when they are reversed, allowing for higher speeds. When micro-stepping, the voltage changes are small. Cheers, Peter --------------------------- Peter Homann http://www.homanndesigns.com/store On Wed 02/05/12 1:28 PM , Jon Elson wrote:andy pugh wrote: > On 1 May 2012 12:26, cogoman 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/ [1]" target="_blank">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 [2] ------------------------- Message sent via Atmail Open - http://atmail.org/ Links: ------ [1] http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ [2] http://webmail.homanndesigns.com/parse.php?redirect=https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ 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
