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. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ 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
