I assuming that you mean by "not terminated" you mean that you simply do not have a pull up or pull down resistor on the two lines. The parallel port outputs can typically sink 24 ma but can only source 2-3ma. You would want to add pull up resistors to +5 in order to improve the signal levels. Adding pull down resistors will only decrease the high voltage level of the signal into your stepping motor control. Use 470 ohm resistors and that should be fine. Depending on what your logic inputs are (TTL, CMOS, etc) to the stepping motor controls, you may be fighting a ground noise issue. That I couldn't address without knowing what the circuitry looked like.
best regards, Steve Thatcher -----Original Message----- >From: Steve Robertson <stee...@ccvn.com> >Sent: Mar 28, 2010 10:06 AM >To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> >Subject: [Emc-users] Breakout Board Problems > >Hey Guys, > >Been testing my machine and am having trouble with random movement of each >of the axis. I believe the problem is because the input to my homemade >driver boards is high impedance and the STEP and DIRECTION lines are not >terminated. Any voltage spikes or EM interference in the immediate area, >like the laminate trimmer that I'm using as a cutting tool, seems to cause >the problem. > >To supress (hopefully) the problem, I figured I'd just put termination >resistors on the breakout board. So... I'm guessing the value of the >termination resistors would not be critical but, surely, there is a correct >value. What would be the correct value for a resistor between the STEP / >DIRECTION signals and Ground? > >I'll also add some decoupling caps to the Power Supply lines to stop any >potential problems there. > >TIA, Steve Robertson >steverob [at] ccvn [dot] com > > >------------------------------------------------------------------------------ >Download Intel® Parallel Studio Eval >Try the new software tools for yourself. Speed compiling, find bugs >proactively, and fine-tune applications for parallel performance. >See why Intel Parallel Studio got high marks during beta. >http://p.sf.net/sfu/intel-sw-dev >_______________________________________________ >Emc-users mailing list >Emc-users@lists.sourceforge.net >https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users