Hi Wayne
Thanks for your quick reply....!
The drives a homemade . I had pcbs made , I am using a Pic18f252 with encoder circuitry , the final output drives a h-bridge mosfet irfz48 x 4 .The 12vdc 10amp motors are connected via shielded cable aswel as limit switches and encoder using separate shield cable and a star point grounding to earth.
The code I wrote using ccs c . I also wrote a vb program that I use to setup the pid and all relavant settings for each drive via RS485 addressable.
I have run tests using the vb program for hours with no errors at all (basically jogging forward 100mm then back repeatedly).Then whether or not with the isolated RS232/RS485 cable plugged in to the PC and drive, I get this run away problem .This happens in random and sometimes not at all.
The step pulses and inrush pulses are clean clean. I seems to happen only when I mill wood in a long straight line of +-300mm.
I am open for any suggestion ....Thanks.