PLC Programming Basics 2013 Eaton Corporation All rights

PLC Programming Basics Basic Ladder Logic “Bit” Instructions Set Reset One-shot Rising or Falling

PLC Programming Basics Instruction Addressing • Input and output bit instructions are addressed with either actual (physical) digital I/O addresses or internal storage bit addresses. • These addresses are defined by the PLC © 2013 Eaton Corporation. All rights reserved. 3

PLC Programming Basics Instruction Addressing • easy 500 controllers use “Markers” for internal addresses such as M 01, M 05, N 11 • easy 500 controllers use Ixx for actual (physical) Input addresses and Qxx for Output addresses. Example: I 01, I 08 are Inputs and Q 01, Q 04 are Outputs © 2012 Eaton Corporation. All rights reserved. 4

PLC Programming Basics Instruction Addressing • Marker addresses (Mxx) are internal storage addresses defined by the controller. They are used as internal relays • Real-world Input and Output addresses must correspond to the actual (physical) input terminal as defined by the controller © 2012 Eaton Corporation. All rights reserved. 5

PLC Programming Basics Read real world inputs Evaluate ladder Write real world outputs ©

PLC Programming Basics Inputs • Input instructions change state when power is applied to the input terminal with the corresponding address • It’s common to call the following instruction “True” rather than “Closed” when power is applied to the terminal its addressed to © 2012 Eaton Corporation. All rights reserved. 7

PLC Programming Basics Inputs • It’s also common to call the following instruction “False” rather than “Open” when power is applied to the input terminal it’s addressed to © 2012 Eaton Corporation. All rights reserved. 8

PLC Programming Basics Outputs • Outputs “energize” when rung conditions preceding them are “True”

PLC Programming Basics Set/Reset • A Set instruction remains True even after the rung conditions that made it True become False • A Set instruction must be accompanied by a Reset instruction addressed with the same address in order to reset the bit, based on your logic © 2012 Eaton Corporation. All rights reserved. 10

PLC Programming Basics Set/Reset Example Input 1 sets Output 1 and Input 2 resets

PLC Programming Basics In 1 Timer 1 Out 1 In 2 Out 2 Ladder is evaluated (scanned) starting from the top rung, left to right, followed by the next rung, and so on, until the bottom is reached. Then starts again at the top. © 2012 Eaton Corporation. All rights reserved. 12

PLC Programming Basics Logical AND/OR Operations If Input A AND Input B are True, the Output will energize If Input A OR Input B is true, the Output will energize © 2012 Eaton Corporation. All rights reserved. 13

PLC Programming Basics AND/OR Combination Logic Output X is energized if A AND (B

PLC Programming Basics - Timers • Two basic types of timers in PLCs: 1.

PLC Programming Basics - Timers • On-delay timers When an On-delay timer is energized (True) it delays turning On the timer’s output bit until the timer’s preset time value is reached. The output bit is often called the timer’s “Done” bit and it indicates the timer has attained its preset time. © 2012 Eaton Corporation. All rights reserved. 16

PLC Programming Basics - Timers • Off-delay timers When an Off-delay timer is energized (True) it immediately turns On its output (Done) bit. The timer then delays turning Off the output (Done) bit for the timer’s preset time, after the timer is de-energized (False). Off-delay timers are less common than On-delay timers. © 2012 Eaton Corporation. All rights reserved. 17