Post on 11-Dec-2015
PowerPoint® Presentation
Chapter 3Electrical Circuits and PLCs
Chapter 3Electrical Circuits and PLCs
Electrical Symbols and Diagrams • Standard Electrical Symbols • PLC Programming Symbols •
Pictorial Drawings • Wiring Diagrams • Line (Ladder) Diagrams • Logic Functions • AND Circuit Logic • OR Circuit Logic • NOT Circuit Logic • NOR Circuit Logic
• NAND Circuit Logic • Electrical Wiring Methods • Direct Hardwiring • Hardwiring Using Terminal Strips
• PLC Wiring
Chapter 3 — Electrical Circuits and PLCs
Switch symbols are drawn to provide a visual indication of how each switch operates in a circuit.
Chapter 3 — Electrical Circuits and PLCs
Any normally open (NO) switch that is manually operated has the operator of the switch drawn above the terminals, and any normally closed (NC) switch that is manually operated has the operator of the switch drawn below the terminals.
Chapter 3 — Electrical Circuits and PLCs
Electrical switches are drawn in normal condition or activated condition on electrical prints.
Chapter 3 — Electrical Circuits and PLCs
Switches are drawn on prints in the operating condition the switch is most likely to be in at any point in time.
Chapter 3 — Electrical Circuits and PLCs
Not understanding how manual, mechanical, and automatic switch symbols are drawn makes circuit understanding and troubleshooting difficult.
Chapter 3 — Electrical Circuits and PLCs
Solid-state switches start and stop the flow of electricity in a circuit without the use of moving parts. Solid-state switch symbols show the actual switch symbol in a diamond shape.
Chapter 3 — Electrical Circuits and PLCs
Programming symbols for input devices are drawn as generic normally open or normally closed contacts, and all output components are drawn as parentheses.
Chapter 3 — Electrical Circuits and PLCs
Special symbols are used in PLC programming when a PLC has advance control functions.
Chapter 3 — Electrical Circuits and PLCs
Pictorial drawings are used to provide a visual picture of devices, components, and wiring.
Chapter 3 — Electrical Circuits and PLCs
Wiring diagrams show the connection of all devices and components to a PLC.
Chapter 3 — Electrical Circuits and PLCs
Thermocouples are connected to analog PLC input terminals because thermocouples produce a voltage proportional to the measured temperature.
Chapter 3 — Electrical Circuits and PLCs
Line diagrams use standard electrical symbols to indicate what types of input devices and output components are being used in a circuit.
Chapter 3 — Electrical Circuits and PLCs
Standard line diagrams and PLC programming diagrams are similar, although different symbols are used to represent the same device or component.
Chapter 3 — Electrical Circuits and PLCs
All electrical control circuits that use any type of switches to control loads are comprised of switching logic functions.
Chapter 3 — Electrical Circuits and PLCs
All input devices of an AND logic circuit must be activated in order to energize the output component.
Chapter 3 — Electrical Circuits and PLCs
Only one input of an OR logic circuit is activated in order to energize the output component.
Chapter 3 — Electrical Circuits and PLCs
The input of a NOT logic circuit must be deactivated in order to energize the output component.
Chapter 3 — Electrical Circuits and PLCs
Only one input of a NOR logic circuit must be deactivated in order to energize the output component.
Chapter 3 — Electrical Circuits and PLCs
All input devices of a NAND logic circuit must be deactivated in order to energize the output component.
Chapter 3 — Electrical Circuits and PLCs
In direct hardwired circuits, the power circuit and control circuit are wired point-to-point.
Chapter 3 — Electrical Circuits and PLCs
To add forward rotation indicator lamps and reverse rotation indicator lamps to a direct hardwired circuit is difficult because the exact connection points for the lamps must be found.
Chapter 3 — Electrical Circuits and PLCs
To make modifications to direct hardwired circuits typically requires the removal and/or addition of circuit wiring.
Chapter 3 — Electrical Circuits and PLCs
Hardwiring using terminal strips dramatically simplifies circuit troubleshooting.
Chapter 3 — Electrical Circuits and PLCs
Modifications are easier with terminal strips because most, if not all, of the wires required to make a change are disconnected and reconnected at the terminal strip.
Chapter 3 — Electrical Circuits and PLCs
When using a PLC to control a circuit, all input devices are wired to the input module of the PLC, and all output components are wired to the output module of the PLC.