Working with Discrete IO - MFET 248, Automated...

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MFET 248, Automated Manufacturing III 2/1/2010 Working with Discrete I/O 1 MFET 248 Automated Manufacturing III Working with Discrete I/O T.E. Kostek Spring 2010 Topics • Introduction • Di/Do Applications • Equivalent Circuits • Sinking/Sourcing defined based on current flow • Sinking/Sourcing defined based on the field 2 wiring • Wiring NPN and PNP proximity sensors • Di/Do Design
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MFET 248, Automated Manufacturing III 2/1/2010 Working with Discrete I/O 2 Introduction Introduction - Sources of Information • Product data sheets/user manuals S ifi ti d i i di f di t d l – Specifications and wiring diagrams for discrete modules are well documented in the publication: “Discrete I/O Modules – Installation Instructions” (publication 1746-5.3-September 1997 or later) • Screen printed wiring diagrams printed on devices (PLC I/O modules, sensors, etc.) 4 – Allen-Bradley DC discrete I/O modules are labeled “Sinking” and “Sourcing”
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MFET 248, Automated Manufacturing III 2/1/2010 Working with Discrete I/O 3 Introduction • This document will focus on PLC discrete inputs (Di) and discrete outputs (Do). • Discrete signals are either fully on or fully off (analog signals are not considered in this course). There are no ANSI standards with respect to 5 • There are no ANSI standards with respect to interfacing discrete signals. Introduction • Di/Do interfacing is: – The most common form of communications (integration) found on the shop floor – The simplest form of communications found on the shop floor 6 – Often used in conjunction with other types of communications (such as RS-232 serial interfacing, and Local Area Networks)
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MFET 248, Automated Manufacturing III 2/1/2010 Working with Discrete I/O 4 Introduction •AC v s . DC – Di/Do interfacing can be accomplished using either AC or DC circuits – These notes will focus on DC interfacing, specifically using 24 volts DC 7 – With DC interfacing, the user must supply an external power supply (in addition to the PLC power supply) Introduction • Direction of current flow: – Conventional current flows from + to - – Electrons actually flow from - to + – We will use Conventional Current Flow unless otherwise specified. 8 Electron flow Conventional current flow
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MFET 248, Automated Manufacturing III 2/1/2010 Working with Discrete I/O 5 Introduction • Sinking vs. Sourcing – Sinking and sourcing generally refer to the direction of current flow – The terms sinking and sourcing are used exclusively with DC interfacing (not AC interfacing) – Sinking generally means that current flows into a device 9 – Sourcing generally means that current flows out of a device Introduction Sourcing Device : Example Devices : Current flow Sinking Device: PLCs Robot controllers Sensors 10 Current flow pushbuttons pilot lights etc.
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This note was uploaded on 02/29/2012 for the course MFET 248 taught by Professor T.e.kostek during the Spring '10 term at Purdue University-West Lafayette.

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Working with Discrete IO - MFET 248, Automated...

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