19 What electronic element can be used as the switching devi

19. What electronic element can be used as the switching device for a 120 VAC discrete output interface module?

20. With reference to discrete output module current ratings:

a. What is the maximum current rating for a typical 120 VAC output module?

b. Explain one method of handling outputs with larger current requirements.

this is the book of Programmable Logic Controllers 5th eidtion FP

Solution

programmable logic controller might be used for this application. The same input

field devices (pressure switch, temperature switch, and pushbutton) are used. These devices would be

hardwired to an appropriate input module according to the manufacturer’s addressing location scheme.

Typical wiring connections for a 120 VAC modular configured input module .The same output field device (motor starter coil) would also be used. This device would be hardwired to

an appropriate output module according to the manufacturer’s addressing location scheme

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two most common types of discrete signals are 120-volt AC and 24-volt DC signals. Accordingly, there are two input interface configurations available in the MicroLogix 1000: 120-volts AC and 24-volts DC.

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A programmable controller operates by examining the input signals from a process and carrying out logic instructions (which have been programmed into its memory) on these input signals, producing output signals to drive process equipment or machinery. Standard interfaces built-in to PLC allow them to be directly connected to PLCs require shorter installation and commissioning times than do hard-wired systems. Although PLCs are similar to \'conventional\' computers in term of hardware technology, they have specific features suited for industrial control: (a) Rugged, noise immune equipment; (b) Modular plug-in construction, allowing easy replacement or addition of units (e.g. input/output); (c) Standard input/output connections and signal levels; (d) Easily understood programming language; (e) Ease of programming and reprogramming in-plant; (f) Capable of communicating with other PLCs, computers and intelligent devices; (g) Competitive in both cost and space occupied with relay and solid-state logic systems; These features make programmable controllers highly desirable in a wide variety of industrial-plant and process-control situations.process actuators and transducers without the need for intermediate circuitry or relays.