Sunday, February 26, 2012

Input Interfaces MicroLogix 1000





The MicroLogix 1000 utilizes the input interfaces to join with the input devices of discrete. These interfaces include all circuitry required to let the devices of field input to correspond their status to the PLC. The earlier module described that there are 2 versions of the PLC of MicroLogix 1000: a version of 16 I/O and a version of 32 I/O. The version of 16 I/O has 10 input terminals, while the version of 32 I/O has 20 input terminals.

All devices of discrete input send an electrical signal ON/OFF to a programmable controller; though, not all discrete inputs transfer the same electrical signal type. The two majority common discrete signals types are 24-volt DC and 120-volt AC signals. Consequently, there are 2 input configurations of interface accessible in the MicroLogix 1000: 24-volts DC and 120-volts AC.
• The configurations of 24 and VDC 120 VAC input interface
• The functional diversities between the two input interfaces types
• The wiring requirements of each input interface

Input Interfaces 120-Volt AC
Three MicroLogix 1000 models come with an input interface of 120-volt AC, which changes the signal of 120 VAC from the devices input into a low level signal DC that the processor of PLC can read. To understand this translation, you require being familiar with components and wiring the interface.

Components
The input interface of 120 VAC of a MicroLogix 1000 has 3 components:
• The section of power
• The section of isolation
• The section of logic

Section of Power
The section of power accepts the input signal from the device field and translates it into a low-level signal DC with a bridge circuit of rectifier. It then transfers the signal via a filter to reduce bouncing and noise. Lastly, it utilizes a threshold circuit of detection to verify that the signal is legitimate.

Section of Isolation
It goes through the section of isolation after the signal is translated by the section of power. This section utilizes an optical coupler to isolate electrically the sections of power and logic.

Section of Logic
The signal goes in the logic section of the input interface after the section of isolation. This section transfers the recently transformed and isolated input signal to the processor of PLC. The input interface of 120 VAC MicroLogix 1000 also comprises a LED indicator power. This LED designates whether the interface is receiving an official signal from the device of input.


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