admira -> RE: Anybody know how to program a ladder? (12/31/2009 10:03:35 AM)
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The numerical format of the address depends on the scheme used by the particular manufacturer, and it may be stated in a binary-based numbering system. (See sidebar on page 26.) A name may also be associated with each address (shown above the instruction in Fig. 1) to make the ladder diagram easier to interpret. Types of instructions Ladder diagram programming allows PLCs to perform several different types of tasks, including Boolean logic, timing, counting, arithmetic, and special functions. We'll discuss the basic instructions and function block instructions, which are common to nearly all PLCs. In addition to these instructions, most PLCs support many extended instructions to perform more complicated tasks. Boolean logic. Boolean logic is actually what PLCs and relay systems perform. The legal operations in Boolean logic are AND, OR, and NOT. The AND operation simply means all of the inputs must be ON for the output to be ON; it's analogous to relay contacts connected in series. The OR operation means that the output is ON if at least one of the inputs is ON; it's analogous to relay contacts connected in parallel._______________________________________________________________________mazda air conditioning compressor mitsubishi shogun cars
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