On Sunday, April 15, 2012 11:55:24 PM Kirk Wallace did opine: > On Sun, 2012-04-15 at 21:37 -0400, gene heskett wrote: > ... snip > > > What happens if the pump frequency is reduced to say 10% of what its > > set at now? > > I haven't tried that. If I disconnect the G540 so there is no load on > the parallel port pin, the charge pump is a clean square wave. I used > 10x on the probe, if that makes a difference (I know just enough > scopenese to get by). > > > Looking at the scope traces, either the probe is way out of > > calibration against the scopes own test square wave, or the 540 has a > > low value series resistor, 33-120 ohm range, with several hundred pf > > on the other side of the resistor as a noise filter on that input, > > and likely on all inputs since engineers have a tendency to 'step & > > repeat' for that stuff. > > I tried to trace the traces on the G540. From the pump input wire > terminal, the trace goes right to an unmarked SMT capacitor. The other > side goes to the center of a three pin SMT something-or-other. My guess > is it is a transistor, maybe. Another of the three pins goes to the > opto-isolator. I gave up tracing at that point. > > > I can't believe you would long tolerate a probe that far out of > > adjustment Kirk, so that leaves the 540 apparently suffering from way > > too much noise filtering on that input. So the pumping frequency is > > so high the capacitor used for noise filtering never has a chance to > > either fully charge, or to fully discharge. So you get insufficient > > swing. > > The G540 manual specs a 10kHz minimum, so the filter doesn't need to > pass the low end. The large C is a bit of a mystery so far. One thing > that stands out to me is the rising edge is near vertical until about 2 > Volts then dog legs up. I expected to have a continuous smooth curve > from O Volts until 5 Volts or when the pin switches. > > > So drop the pump frequency to 10-20% of what it is now just for > > effects, would be my advice. If it drops out because the pump is > > then too slow, the 540 needs a redesign tweak, at least according to > > Gene. :) > > > > Cheers, Gene > > My favorite fix so far is to recomend a buffer board on the parallel > port. It's the only thing a user could add that would cover most every > parallel port and the G540. A user would have a harder time fixing the > G540 or the port. I need to find a loose buffer card around here and try > that next. While I'm at it I'll check too see what happens with a slower > pump.
My fav 'buffer' card ATM, is Arturo Duncans C1G, all opto-isolated with about a 10 ns relay time, and can src or sink 24 ma on any pin. Tallying LED's present on all pins for instant troubleshooting. <http://www.cnc4pc.org> I think, might be a .com. I am using one in both the mill and the lathe. Once programmed with its flea clips, it Just Works(TM), with very close to a full 5 volt rail to rail output. You can program the inputs to have a pull resistor to either rail. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> Doctors and lawyers must go to school for years and years, often with little sleep and with great sacrifice to their first wives. -- Roy G. Blount, Jr. ------------------------------------------------------------------------------ For Developers, A Lot Can Happen In A Second. Boundary is the first to Know...and Tell You. Monitor Your Applications in Ultra-Fine Resolution. Try it FREE! http://p.sf.net/sfu/Boundary-d2dvs2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
