An intrinsic safety PLC with a graphic programming environment

An intrinsic safety PLC has been developed. This PLC has been built to be used in dangerous environments, such inside mines, where there are risks of explosions. A MC68000 microprocessor has been used as the processor and the PLC incorporates a security system based on the use of fiber optics and the MC68HC11E2 microcontroller. Moreover, conventional digital and analog I/O cards are used. There are two levels of programming, a textual level and a graphic level. The PLC is programmed from a personal computer through a serial port. It is programmed offline.