I've being doing some programming stuff for my company, for some years. last year I came across one of the machines I had installed a PLC into.
The inputs of the PLC were ZAPPED!!! I dont know if someone tried to do WELDING on the machine without disconnecting or probably dropped a LIVE wire on the machine.
There are reasons that all the machine's sensors cannot be replaced by elec. ones.
Most of these are mechanical type devices giving out signals (-0V or earth). The older systems used these so called detectors and were used in the interlocking.
As for some reason these cannot be replaced (only improved, somewhat), I want to evade such silly things. I wire the COMMON of the Input with a 24V and some NPN sensors and these "DETECTORS" are used as inputs. (and no the electrics here are not that good, and most safety devices, such as short circuit proctecting ones, ELCB, etc are disconnected)
can someone suggest a good way to protect (somewhat insulate) the inputs while using these "DETECTORS" in this environment!!
I was thinking of using DIODE at each of such INPUT, comments?
The inputs of the PLC were ZAPPED!!! I dont know if someone tried to do WELDING on the machine without disconnecting or probably dropped a LIVE wire on the machine.
There are reasons that all the machine's sensors cannot be replaced by elec. ones.
Most of these are mechanical type devices giving out signals (-0V or earth). The older systems used these so called detectors and were used in the interlocking.
As for some reason these cannot be replaced (only improved, somewhat), I want to evade such silly things. I wire the COMMON of the Input with a 24V and some NPN sensors and these "DETECTORS" are used as inputs. (and no the electrics here are not that good, and most safety devices, such as short circuit proctecting ones, ELCB, etc are disconnected)
can someone suggest a good way to protect (somewhat insulate) the inputs while using these "DETECTORS" in this environment!!
I was thinking of using DIODE at each of such INPUT, comments?