On Thu, Apr 07, 2011 at 08:10:55AM -0400, gene heskett wrote: > > An additional thought comes to mind when using them for something like my > A3877 based xylotex setup, an extended time at low voltage is not > recommended as it causes more heat in the A3977's than the normal voltage, > so its possible it could actually increase the 'turnon' failure rate of > such devices if its too slow to warm up.
Gene, you're beginning to convince me there's no such thing as a free lunch, and I'd be just as well off going back to my MOSFET idea, which leaves a fat (low value) power resistor in series for enough mains cycles to charge the capacitor bank, then shunt it with about 5 milliohms of drain resistance. (In addition to your favourite source, I have a tube of 'em waiting to serve man and country. And what's in the junkbox is kinda prone to being designed in.) Since we only need enough resistance to limit a whacking great inrush current, that'll bring up the supply for the control electronics within a few mains cycles. I think we'd take a few breaths before starting the gcode program and firing up the motors. If the MOSFET is hard on within a few hundred milliseconds, then I'd hope stuff like your A3977's would be fine, especially since they'd be idling at the time. I think drives have to provide their own current limiting once we have lift-off. (And they generally do.) Erik -- I have long felt that most computers today do not use electricity. They instead seem to be powered by the "pumping" motion of the mouse! - William Shotts, Jr. on http://linuxcommand.org/learning_the_shell.ph ------------------------------------------------------------------------------ Xperia(TM) PLAY It's a major breakthrough. An authentic gaming smartphone on the nation's most reliable network. And it wants your games. http://p.sf.net/sfu/verizon-sfdev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
