On Wednesday 12 December 2007, Emory Smith wrote: >Thanks for all the suggestions! >I'm making progress. Installed EMC 2.2.1 from the latest live CD and am >experimenting with steplen & dirhold that I didn't have in 2.0.1. >Adjusting acceleration on the Y axis has helped too. >Getting a nice ramp up and down. > >After running stepconf, I have a configuration with these values: >steplen 1, stepspace 0, dirhold 36920, dirsetup 36920 >Changing steplen to 2, dirhold & dirsetup to 75000 helped. Fewer dropped > steps. Left stepspace at 0 because of no docs on it. >Didn't know whether to double it or half it ;^) > >In my hal file, "setp parport.0.reset-time 5000" is new to me. >Any reason to change it? > >Are the dirhold & dirsetup numbers nanoseconds? > >Can't find info on what stepspace & dirsetup do. >Any hints where to look? > >I can sometimes hear the stepper "bump" when it drops a step. >Tomorrow, I'll put an oscilloscope on 2 of the leads to the Y motor, >run it and watch for anomalies in the waveform that coincide with the >"bump" sound. (It'll only do it whenever I look away, of course ;^)
Murphy's Law at its finest. :) Background: I'm a C.E.T., and have had a scope probe in one hand since 1951. Do not scope the motor leads unless you are using both channels of a dual trace scope in the inverted & add mode, scoping both wires, as grounding any part of that with the ground lead of the probe will instantly total the amplifiers. The scope should have at least 100mhz bandwidth and the probes should be precalibrated so that the test square wave on the front of the scope is indeed square and flat top and bottom when observed. Also, do not use probes without the 10x attenuation enabled as the added capacitance of a direct probe may|will also total the amplifiers. Most folks don't recommend even getting that close to the motor leads, its a very critical point that should have only an inductive load associated with it. An extra 50 pf's of scope probe can raise the current thru the switches in the amplifiers at the transition point, where most of the heat is generated, by an order of magnitude. Informational wise for this sort of troubleshooting, scoping the step and dir signals *to* the amplifier, and comparing the rise times, steplen times and dir setup times to what the amplifiers need will probably be far more usefull. A parport that doesn't have adequate drive will be not only slow, particularly the pullup times, but may not have the source and sink current cajones to satisfy the amplifiers input voltage requirements even with arbitrarily long steps. This is not an uncommon problem. >These questions were asked of me in this thread: >What stepper drive? Stepper3. Rated 25V @ 1A. 1MHz max >What stepper motors? Vexta PH265-04-C18, 1.8"/step, 5V 1A Humm, smallish motors, and the 5v 1 amp would indicate higher than normal inductance, which will limit the maximum speeds vs usable torque. These are single stack nema 23's I take it? From the pix & description, yes. But I also don't think this is related very closely to the skipping step problem, that's more often than not, parport or cabling problems from the parport to the amplifiers or miss-configured software. >Thanks again, HTH -- 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) If time heals all wounds, how come the belly button stays the same? ------------------------------------------------------------------------- SF.Net email is sponsored by: Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
