When we talk of digital I/O this is referring to the individual bits that you can wire switches, pushbuttons, proximity sensors, or any other device that is either on or off. Discrete On/Off Bits in the PLCĭiscrete bits are the basic building blocks in the PLC.
WHAT IS NORMALLU OFF BIT IN GX WORKS 2 MANUAL
Refer to the manual of the specific PLC that you are using for the way in which memory is addressed and if it is memory retentive or not. Indirect Addressing: Specify a location that contains a value to point to the memory location required. When we address memory in the PLC we can do this in two different ways:ĭirect Addressing: Specify a location of the memory location Addressing refers to how the controller understands what memory location to look at. If the bit is non-memory retentive, and power is lost the bit returns to the off state. Memory retentive means that if power is lost to the PLC, the status of the bit remains the same when power is restored. The memory can be retentive or non-memory retentive. Understanding the different ways in which we can view these bits will help in developing programs.īits are part of the memory of all PLC systems. Discrete input and output, Numbers and Position of bits will be covered. In general, there are several ways to view the bits. The instruction set is the method we use to do this. It is these bits that we manipulate in order to accomplish the work that we need to be done by the PLC. Every PLC company will do this…Įverything in the programmable logic controller actually boils down to bits in the memory.
Today we are going to look at the basic fundamental way we program. Programs are written to look at the inputs solve logic and set the outputs to perform work. A programmable logic controller (PLC) is a piece of hardware that isolates inputs from outputs. When timer done turned on, close door motor should ON until closed limit switch is turned ON.People often ask “What is a PLC?” and “PLC Meaning”. When the open door limit switch is turned to on, the Open motor door should stop and timer needs to turn on to give time delay of 5s to close door motor. RUNG 0016įrom the previous rungs memories, an Open door motor is turned ON with three interlocking like closed-door motor, Timer enables, UP/DOWN motor. To open the lift door when it reaching the floor, Binary bits are used to store the status of Third floor PB and third-floor Limit switch. To open the lift door when it reaching the floor, Binary bits are used to store the status of First floor PB and First Limit switch. To open the lift door when it reaching floor Binary bits are used to store the status of ground floor PB and ground Limit switch. In some cases, if someone pressed the second floor PB/First-floor Pushbuttons (PB), the program will check where the lift is, if it is in the ground floor or the first floor, UP Motor will turn ON to get the lift to the respective floor.įor interlocking, normally closed switch of second-floor limit switch and first-floor switch is used in Rung 0009 RUNG 0010, 0011 In some cases,if someone pressed ground floor PB/First floor PB, the program will check where the lift is if it is in the second floor or the first floor, Down Motor will turn ON to get the lift to the respective floor.įor interlocking, normally closed switch of ground limit switch and first-floor switch is used in Rung 0006 Rung 0007, 0008, 0009
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