Re: Try/Catch
- Posted by Shian_Lee Jan 07, 2015
- 5841 views
I've been a controls engineer for decades.
RSLogix 5000 for Allen-Bradley Logix line of PLCs (or PACs - Programmable Automation Controller) has a special folder called "Controller Fault Handler". This is for special code that, surprisingly enough, is for CATCHING major faults (i.e. not if a sensor isn't acting correctly, but if, say, a whole input module is dead), then handling the fault in an, hopefully, orderly fashion, such as shutting the machine down gracefully if possible.
Siemens does the same thing with special Function Blocks
Since you are an engineer, let's be honest. How many controllers are out there? How many of them are truly able to deal with failures? How many programmers are actually care about it?
How many electricians are connecting the controller to the E-stops as recommended?
I've seen a big machine, made in Germany, where many, actually all, the E-stops were connected in serial - not parallel. Again: made in Germany. And with no external power supply for double safety.
We all are saving money, time and... disappointments. After all, even if the controller part is perfect - in case of emergency stop there's no way to release the hand/head of the worker from the conveyor-belt since the designers of the machine 'forgot' to supply manual reverse.
I've never used any exception handler in controller, and among the other programmers I knew, I'm considered to be very cautious.
At least we still have Euphoria 3.1.1 to enjoy the real thing. And we can kill the exceptions by calling DOS interrupts directly where needed. Machines love DOS.
