The student is first offered with a menu which facilitates either the PLC Tutorial (PLCTUT), the PLC Simulator (PLCSIM), or EXIT to be chosen when using the courseware.
PLCSIM A virtual PLC
The approach accepted is to reproduce, not essentially all the features but as strictly as possible, a real PLC, the Toshiba EX20PLUSin effect to make a virtual PLC. The EX20PLUS PLC contains of a major unit and a removable programmer. The screen of simulator displayed to a user. Shown on the display is the virtual Toshiba EX20 PLC major unit, a removable PLC programmer with a LCD, and a table status which shows the current settings of internal (R), latch (L), and output (Y) counters, coils, and timers. Linked to the inputs is a replicated input of switch simulator.
The PLC programmer simulation allows the user to enter and amend programs. The keyboard includes 35 keys which are color coded to help programming. The keys are utilized for specifying devices, for example contacts, coils, counters and timers, and for entering commands and instructions. A key is triggered by positioning to it with the pointer of mouse and clicking the left button of mouse. A graphic programming form is engaged in which symbols of ladder diagram are entered from the keypad on the programmer and the necessary ladder diagram is developed and showed on the LCD monitor. The LCD simulation screen includes three areas: a line of message which shows different information depend on the programmer mode; a line of mode which points to the programmer current mode; and a area of ladder diagram which can contain of up to 8 rungs.
After a whole ladder diagram is keyed in by a user on monitor, it is then downloaded to the PLC simulation. To operate the program, the mouse is utilized to indicate the switch of HALT/RUN on the major unit. Pressing the left button of mouse then adjusts the switch state to RUN and the program of ladder diagram is performed. The software simulator constantly reads the inputs, realizes the ladder diagram and updates the outputs. As noted, the inputs and outputs status can be examined by monitoring the states of the two sets of input and output LED simulation indicators on the major unit. The table status can be utilized to give information on the existing settings of timers, counters and coils. The intention is to offer a user with a system which has the look and feel of a actual PLC with the simulator.