We all know how important time is in our lives. Whether it is a human or a machine, it cannot be done without time.
Everything around us is evolving towards automation. Here, our PLC (Programmable Logic Controller) plays a big role.
In PLC automation, there are different types of PLC programming instructions with different specifications for us to use.
Among these PLC ladder diagram (LD) programming instructions, the timer instruction is one of the most important instructions, and it plays a very important role.
This time, I will describe the PLC timer in detail through programming instructions and functions.
Let's start from scratch.
directory
What is a PLC timer?
Basic internal circuit of PLC timer 1.Input and output module 2.Power module 3.Internal timer circuit 4.Timer digital display
What is the type of PLC timer? 1.Turn on delay timer (TON)2.Turn off delay timer (TOFF)3.Hold on/off timer (RTO)
Timer instruction address 1 for multiple PLC brands.Addressed for ABB PLC 2. Addressing of AB (Rockwell) PLC 3.Address of Siemens PLC 4.Addressing of Delta PLC 5.Address of Mitsubishi PLC
Example based on PLC timer instructions
What are the applications of timer instructions?
<h1 style="text-align: center;"what is a PLC timer >? </h1>
A PLC timer is a command to control and operate a device during a specific period of time. Using a timer, we can perform any specific action within a specific period of time.
We can set up time-based activities with the help of PLC programming timer instructions. Each PLC has a different timer function.
Timer instructions are used to provide programming logic and determine when to turn a circuit on or off. It has normally open (NO) or normally closed (NC) contacts.
Let's see here the representation of input and output timer NO and NC contacts in LD programming.
The timer output contacts are displayed in coil form or box form or rectangular form. In AB and Siemens PLC, it is represented in a box shape.
If you want to perform work or device activities within a specific time frame, you must be familiar with timers. To do this, we must learn the I/O timer instructions used to write PLC programs.
In ladder diagram (LD) PLC programming, we can set the PLC timer from milliseconds (ms) to hours (hr) time range.
Let's look at the internal circuitry of the timer.
<h1 style="text-align: center;" > the basic internal circuitry of the PLC timer</h1>
Now, we're looking at the PLC's internal timer circuit. The operation of the timer circuit is based on four main parts.
Each internal part of the timer circuit has various functions. This is how they are connected and constructed in a given diagram.
Here are some basic terms we need to know about timers used in PLCs.
<h1 style="text-align: left;">1</h1>
The module that interacts with the input signal is called the input module. The input module needs to be connected to a timer circuit to provide an input signal.
The module that interacts with the output signal is called the output module. The output module is required to be connected to a timer circuit.
<h1 style="text-align: left;">2</h1>
The power module provides power for the normal operation of the timer circuit. It can be connected to an AC voltage source (e.g. 120, 230 V AC) or a DC voltage source (e.g. 5, 12, 24 V DC).
<h1 style="text-align: left;">3. Internal timer circuit</h1>
The timer circuit performs setup and reset functions.
If the auxiliary power supply is "on", the timer provides instantaneous input pulses for setup and reset operations.
<h1 style="text-align: left;">4</h1>
The digital timer displays the set and passed timed values.
For automation, these values can be displayed in milliseconds (ms). This will make it easy to keep track of your automation system.
<h1 style="text-align: center;"What is the type of PLC timer >? </h1>
For ladder programming, the PLC programming timer is classified as -
<h1 style="text-align: left;">1. Turn on the delay timer (TON</h1>).
A time-lapse timer (TON) is a programming instruction used to initiate a transient pulse within a set period of time.
Let's look at the simple construction of the AB PLC delay timer programming instructions.
<h1 style="text-align: left;">2. Turn off the delay timer (TOFF</h1>).
A time-lapse (TOF) timer is a PLC programming instruction used to shut down an output or system after a certain amount of time.
See here, AB PLC off the basic structure of the delay timer programming instruction.
<h1 style="text-align: left;">3</h1>
The main function of the RTO is to save or store the (cumulative) time of the settings.
RTO is used when the step state changes, power loss, or any interruption in the system.
In the AB PLC, the hold timer instructions are shown below.
We can get a brief look at the various types of PLC timers with examples.
<h1 style="text-align: center;"" > timer instruction addresses for multiple PLC brands</h1>
We have seen three timers provide a delay function to control the operation of the PLC. The timer handles four main values.
The timer address
Preset values
The timer base value
Cumulative value
Each timer instruction has three very useful status bits. These bits are...
Enable Bit (EN)
Timer Chronograph Bit (TT)
Completion bit (DN).
In AB and Siemens PLCs, the output bit is often referred to as the "completion bit" of the timer. And it indicates that the timer has reached its preset time.
<h1 style="text-align: left;">1</h1>
In ABB PLC programming, we can simply write the I/O timer address of the ladder graph. We can set the timer value between "T0" and "T255".
You can see the I/O contact representation diagram above.
<h1 style="text-align: left;">2. Addressing of AB(Rockwell) PLC</h1>
For AB PLC, the address range of the timer is from "T4:0" to "T4:255".
where T4 is the file type.
Addressing format for timer instructions with three status bits.
Enable bit (EN) addresses range from 'T4:0/EN' to 'T4:255/EN'.
The timer timer bit (TT) is addressed from 'T4:0/TT' to 'T4:255/TT'.
Completion bit (DN) addresses range from 'T4:0/DN' to 'T4:255/DN'.
<h1 style="text-align: left;">3</h1>
In Siemens, LD programs can be written using five types of timers.
Pulse Timer(S_Pulse)
Pulse Extended Timer (S_PExT)
Delay Timer (S_ODT)
Delay Extension Timer (S_ODTS)
Turn off the delay timer (S_OffDT)
General block diagram of a timer (in Siemens PLC),
Where is it
S – The setpoint or signal of the timer
TV – Time variable. It is used to store time values in the following form:
You can enter a time value between 1 and 9990 seconds.
R - The reset value of the timer
Q – The output of the timer
BI – The current time in binary code
BCD – Current Time (Binary Decimal Code)
<h1 style="text-align: left;">4</h1>
For WPLSoft Software (Delta PLC), you can use timer addressing ranging from 'T0' to 'T127'.
In the Delta PLC, the input timer address is shown in the general representation (T0, T1,...... T127）。 And the output coil is of the form
"T0" is the timer address and "K" is the constant term
Delta PLC timer block diagram:
For Delta PLCs, the timer will start for 10 seconds. It should be written in the form "T0 K100".
<h1 style="text-align: left;">5.The address of the Mitsubishi PLC</h1>
Both Mitsubishi PLC and Delta PLC use the same timer addressing format.
<h1 style="text-align: center;" > an example based on PLC timer instructions</h1>
The most basic and practical example is the use of PLC automation to control traffic signals.
After a certain (fixed) time, each side signal must be turned on and off. Only one side traffic light should be turned on at a time.
This logic can be implemented using a simple PLC timer.
<h1 style="text-align: center;" What are the applications of > timer instructions? </h1>
Here are some basic applications for timers that can be used in a PLC automation environment.
Used to delay an action
Used to run or stop an operation based on a user command.
RTO timers help record or maintain intermediate time values.
It's all about PLC timers. This is a topic that can be said for many, many more. I'm just going to say it briefly this time. If you have any questions, please feel free to ask them in the comments.
If you want to apply the plc timer in detail, we'll talk about it later.