Programable Electronic Controller (PLC)
The following technical information is From Automation Direct.com
A Condensed Guide to Automation Control System Specification, Design and Installation - T. Elavsky - Automation Direct
Relays Show Staying Power: As Their Control Capabilities Increase, Relays Encroach on PLCs - Jim McConahay contributes to this article outlining advantages of relays and programmable relays over PLCs. Relays have many electrical and safety advantages over PLCs, and programmable relays can outshine PLCs in real-time control and monitoring. From Moore Industries-Pacific, Inc. and Control Design.
Automating Manufacturing Systems with PLCs- This is a sensational 846 page book full of information on PLCs, logic design, Sensors etc - from Grand Valley State University and written by Hugh Jack- A 5.4Mbit download but worth the wait!
PLCs - Terminology,Tools, Tables and Calculator s- From Controlsweekly.com.
PLC Glossary of Terms - A complete glossary of the most often used terms in PLC systems - from www.industrialtext.com.
PLC Primer - A very useful 16 page document from www.industrialtext.com with all the basics about PLCs.
PLC Basics - A fantastic 39 page tutorial and associated exam from Eaton Electrical.
PLC Resource - Lots of great technical papers and tools here - From PLC Open.
Your Personal PLC Tutor Site - From PLCs.net.
PLC Basics - From the PLC Man.
Basics of PLCs - A tutorial from Siemens.
Primer on Programmable Controllers - Thomas A. Hughes - A useful introduction to PLCs which details basic components, I/O System & Structure along with Input & Output Types - from ISA and InTech.
Troubleshooting the Workhorse of Engineering Industry - the PLC - Steve Mackay - One of the workhorses in industry - no matter whether you are in industrial automation, electrical or mechanical engineering, you are likely to be confronted with one of these little fellahs - a Programmable Logic Controller or PLC (or indeed, Programmable Automation Controller - PAC). A critical cheap building block for all automated systems. Effectively, an industrially hardened digital electronic device in which a sequence of instructions are stored, which enable the PLC to replace hard wired relay logic and perform counting, sequencing and timing. As well, as reading analog inputs (e.g. from a flow meter) and outputting analog output control signals to valves and other control devices. A few tips on troubleshooting these devices are detailed in this blog (yes - the veterans amongst you will sigh, when you know your enormous depth of experience built up to do this - as against my short note below). I have presumed in the suggestions on troubleshooting, that your PLC has been operating correctly and there are no recent program changes.