On Mon, 2012-06-04 at 20:37 -0400, jeremy youngs wrote: > hello beginning to finally assemble my machine, my steppers are rated 11 > amps ive been unable to locate any drives at less than300 ea that will > handle this current, so I want to know with lcnc doing all of the steps > does it microstep and can i drive an isolated mosfet h bridge directly from > this with a current regulated supply? This is my first conversion it is a > 9x 42 table my steppers are 450 oz in. Do i need that much I figure the > larger the better but sourcing a driver is becoming difficult thanx guys
Just as a reference, my Shizuoka mill (3,000 lbs for the base machine) is a little bigger than my Bridgeport mill with a 9 x 42 table (not XY travel). http://www.wallacecompany.com/machine_shop/Shizuoka/00018-1a.jpg http://www.wallacecompany.com/machine_shop/Shizuoka/ It has stepper drivers rated for 8 Amps at 45 Volts (or 360 Watts each). The driver inputs go to each unipolar channel (4 per driver). LinuxCNC drives each input with step type 9. Bipolar h-bridges would need a different step type. Current limit is PWM controlled on the driver board. http://www.wallacecompany.com/machine_shop/Shizuoka/Driver%20Schematic1.jpg Generally, amperage determines torque and voltage determines speed. It seems at some power level the FET's become much harder to control, so the drivers become much more expensive. I believe the problems are in getting the FET's to turn ON and OFF reliably and on time, and preventing shoot-through (having the high and low side FET on at the same time creating a short). There are some high current drivers from robotics suppliers like this Solarbotics driver: http://www.solarbotics.com/product/50120/ but usually have lower voltages, 30 Volts in this case, for running from batteries. I seem to recall Mesa has some higher power bridge drivers: http://www.mesanet.com/motioncardinfo.html -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ 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-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
