Chris, there are as many ways to tie interlocks as there are programmers but I will relate my experiences to you. On anti-tie downs we use a timer to make sure that the buttons must be made and opened. Use the ENABLED bit to allow the program to step and the DONE bit to make sure the buttons are not taped down. On interlocks we usually have them inserted in the AUTO operation rung so the machine will not go into operation with an unsafe condition. PLC's sure beat having to meter 30 or so relay contacts to see where the problem is, besides we use a PC to troubleshoot them so I get to play on a computer and get paid for it! Almost criminal isn't it!
[This message has been edited by spkjpr (edited 03-28-2002).]
