Greetings all; While I like the SPI interface as its faster that even a parport, I am finding it quite susceptible to mistakes cause by emi from a switching psu's typical of stepper motor psu's. These things it seems can radiate back out the line input connections, while switching at 17 kilohertz, is making the whole system bounce around with high frequency switching noises of 5 or more volts with rise times in the sub 5ns range, 2 feet of ground braid away from the common bolt, totally tearing up the data integrity of the spi bus.
With the z motor psu unplugged, the system runs fine although the noise from the 5 v 4a computer and interface supply is still in the 1.5 volt range, measured from the common ground bolt to a grounded pin on the 7i90's center i/o connector. A filter of sorts, with too long (about a foot) interconnection leads from that 5v supply to the filter reduces that noise to about 400 millivolts, so its definitely helpfull. So I have bought 2 of corcoms 20 amp rated brick wall's, should be here the end of next week. $24/copy. So my question is: If I mount one adjacent to the psu's for the motors, and feed both psu's from that filter with lead wires in the 2 or 3 inch range, is this going to cause the crap from one supply to be rejected into the other supply, possibly damaging it? Both supplies carry universal, up to 250 volt input ratings. In fact I'd feed them 254 from the wall plug, except the inputs are labeled L & N, not L & L. Being a std residential hookup here, my 254 is centertapped, balanced to ground. 127 vac to dirt ground from either leg. The 2nd, I will strip room for it on the inside of the lid, so that the little supply also has very short leads to the filter. I quit adding a third one for the 2nd supply because I an running out of mounting space for it in this box. So I almost have to make one filter do for both supplies. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
