Just reminiscing about some of my early days of using PLC's, the first one I replaced was relay logic, this was a cutting press with 12 different cutting patterns, with probably a hundred plus relays, the paper diagram was about 20 feet long, many interesting features where some contacts were in the cold sides of the coils I must admit pretty clever in reducing the number of relays.
We replaced it with a SQD Symax 300, there was no way of putting contacts on the cold side of the coils so ended up being a long winded job, we had no idea what the patterns were, the guy that used to run it had retired & it had been in storage for a number of years. By carefully reproducing the logic without knowing how it worked, we plodded on, from getting the press running, trying all the switch positions we then could replace the mimic panel with the correct lettering for the switches & control buttons. Incidently, this was a babtism of fire, we were still working on it until nearly midnight on a christmas eve in the early 80's.
Another one was a system that had what only could be described as overgrown integrated circuits for example modules were about 4 inches by 3 inches & 1 inch high with multiple pins, from the descriptions on the modules it was deduced these were discrete transistor logic blocks encapsulated in epoxy resin. Fortunately there was an engineer who knew how this system worked & from his description came up with a program that worked.
Is there anybody out there that has come across a valve control system they had to replace ?.
We replaced it with a SQD Symax 300, there was no way of putting contacts on the cold side of the coils so ended up being a long winded job, we had no idea what the patterns were, the guy that used to run it had retired & it had been in storage for a number of years. By carefully reproducing the logic without knowing how it worked, we plodded on, from getting the press running, trying all the switch positions we then could replace the mimic panel with the correct lettering for the switches & control buttons. Incidently, this was a babtism of fire, we were still working on it until nearly midnight on a christmas eve in the early 80's.
Another one was a system that had what only could be described as overgrown integrated circuits for example modules were about 4 inches by 3 inches & 1 inch high with multiple pins, from the descriptions on the modules it was deduced these were discrete transistor logic blocks encapsulated in epoxy resin. Fortunately there was an engineer who knew how this system worked & from his description came up with a program that worked.
Is there anybody out there that has come across a valve control system they had to replace ?.