DO NOT BELIEVE THAT OPTO ISOLATION IS NOT CRICICAL!!!!!
I have a Fanuc 5 controller on my nc lathe (3 actually). The idiot who I bought it from crafted up a BTR between it and the PC. Ground was ground as far as he was concerned so he tied the ground pins of the parallel to the ground interface for the BTR connect of the Fanuc. Turns out that he did the same for all 3.
The transformer the NC was on was at a different ground potential than the "ground" the PC was on for god knows what reason -(old building, kluged up wiring, whatever).
Result: the PC fried a number of the horribly obsolete TTL interface chips on the Fanuc due to a ground current issue. Let the smoke out of a number of chips REAL quick when that happens...
Trying to get an obsolete 1979 motherboard serviced in 2005 ain't easy. Fanuc wanted something like $4500 for the board (yeah sure - paid that much for the whole lathe). Found a guy in Texas who services them at a very reasonable price (considering) but it still cost several thou to fix them.
Yes, you can run non isolated interface 'tween the PC and whatever. I learned my lesson and WON'T EVER DO IT AGAIN. You are free to ignore this suggestion but you'd probably be less than intelligent/well informed to ignore it.  |