1. 4/24/05 BAE 3023 1 Motor Control PLCs and Ladder Logic An Introduction

2. 4/24/05 BAE 3023 2 Hard-wired Motor Control Circuitry Thermal protection not shown

3. 4/24/05 BAE 3023 3 Manufacturers wiring diagram

4. 4/24/05 BAE 3023 4 Definitions - PLC –PLC: (Programmable Logic Controller) An industrial control device developed to accept contact closure inputs and to provide outputs that drive relay coils. The device may be re-programmed with code relating inputs to outputs Modern PLCs may allow analog input/output and may support high level language functions (C, C++, BASIC) Programming logic includes simple logic, timing functions counting functions, sequences, and may include complex algorithms (eg. PID) Examples: Allen-Bradley, Schneider-Modicon, GE, Moeller, etc.Allen-Bradley

5. 4/24/05 BAE 3023 5 Definitions - Ladder Logic –Ladder Logic: Graphical language for describing output of an electrical switching system as a function of its inputs. Also known as “relay ladder logic” or RLL Commonly used in PLC coding Primarily used to relate logical inputs (switch closures) to relay coil outputs. (Start switch used to energize a motor contactor relay) Commonly used to document control equipment in process plants Example:

6. 4/24/05 BAE 3023 6 Motor Control Ladder Logic –Note: Power circuit is not shown, only control wiring Left side ladder is source, right is sink Many rungs or “circuits” can be shown

7. 4/24/05 BAE 3023 7 Allen-Bradley Pico PLC Circuit elements –“I” Input contact closures –“Q” Output contact closures (drives coil) –“T” Timer device –“C” Counter device –“M” Auxillary relay –“H” Time of day –“A” Analog input –“D” Display on screen –“R”,”S” Expansion devices

8. 4/24/05 BAE 3023 8 Demonstration Picosoft Demonstrator

9. 4/24/05 BAE 3023 9 Time Delay Time delayed start of conveyor with All STOP

10. 4/24/05 BAE 3023 10 stop and start delay Time delayed start and time delayed stop