PLC

Understanding Different types of Timer blocks used in a PLC ladder logic

In this article we are going to see the different blocks of timer used in Siemens TIA Portal .  The following graph show the different ON and OFF Condition of Timer Block. 

The siemens TIA Portal Timers are:

  1. TP – Pulse Timer
  2. TON – ON Timer
  3. TOF – OFF Timer
  4. TONR – Time Accumulator 

Graphical Representation of different Timer used in Siemens TIA Portal

Understanding Different types of Timer blocks used in a PLC ladder logic 1

Different Timer Block of PLC Ladder Logic using in Siemens TIA Portal V16

  1. TP – Pulse Timer
Understanding Different types of Timer blocks used in a PLC ladder logic 2
  1. TON – ON Timer
Understanding Different types of Timer blocks used in a PLC ladder logic 3
  1. TOF OFF Timer
Understanding Different types of Timer blocks used in a PLC ladder logic 4
  1. TONR – Time Accumulator
Understanding Different types of Timer blocks used in a PLC ladder logic 5

Declaration of Input and Output of different Timer PLC block

Declaration of Input, Output and Others block of TP Timer PLC block

S. NoOperationInput/
Output/
Others
Address of Each Block
1Input Switch for Timer Input%M0.0
2Input Switch for Associated Timer CoilInput%M0.1
3Pulse Timer BlockTimer (Pulse Timer)%DB1
4Start pulse timerTimer
(Pulse Timer)
%DB1
5Input for Start Pulse TimerInput“IEC_Timer_0_DB”.Q
6Output Load for Timer BlockOutput%Q0.1
7Output Load for Start Pulse TimerOutput%Q0.1

Declaration of Input, Output and Others block of TON Timer PLC block

S. NoOperationInput/ Output/
Others
Address of Each Block
1Input Switch for Timer Input%M0.0
2ON Timer BlockTimer
(Pulse Timer)
%DB2
3ON  Timer Associate BlockTimer
(Pulse Timer)
%DB2
4Input for ON TimerInput“IEC_Timer_0_DB_1”.Q
5Output Load for Timer BlockOutput%Q0.0
6Output Load for ON TimerOutput%Q0.1

Declaration of Input, Output and Others block of TOF Timer PLC block

S. NoOperationInput/ Output/
Others
Address of Each Block
1Input Switch for Timer Input%M0.1
2OFF Timer BlockTimer
(Pulse Timer)
%DB2
3OFF Timer Associate BlockTimer
(Pulse Timer)
%DB2
4Input for OFF TimerInput“IEC_Timer_0_DB_1”.Q
5Output Load for Timer BlockOutput%Q0.2
6Output Load for OFF TimerOutput%Q0.3

Declaration of Input, Output and Others block of TONR Timer PLC block

S. NoOperationInput/ Output/
Others
Address of Each Block
1Input Switch for Timer Input%M0.2
2Time
Accumulator Block
Timer
(Pulse Timer)
%DB3
3Time Accumulator Associate BlockTimer
(Pulse Timer)
%DB3
4Input for Time AccumulatorInput“IEC_Timer_0_DB_2”.Q
5Output Load for Timer BlockOutput%Q0.4
6Output Load for OFF TimerOutput%Q0.5

Different Phases of PLC Ladder Logic of Timer Block Operation

The TIA Portal V16 software from Siemens is used to write the PLC program. According to the above statement, Different PLC timer Blocks are explained int the following Sections.

TP-Pulse Timer

  1. The pulse Timer will be triggered for every positive pulse. Once the Input switch %M0.0 is turned “ON”. The timer starts and run for the period of specified time and stops. 
  2. During the timer is running the output %Q0.0 will be “ON”. 
  3. The TP time output coil (Marked in red). It is associated coil of TP Time block. It can be used any number of times in a PLC Ladder Programming for switching “ON” the different Output. The below figure shows one example of such ladder programming.
  4. The %M0.1 is input for the TP time output coil (Since the Timer will not be connected directly to the Ladder). 
  5. Some other Output %Q0.1 is connected to TP time output relay. Until the TP timer Block “ON” both outputs will be “ON”. Once the TP timer goes “OFF” after specified time, both the load goes “OFF”.
Understanding Different types of Timer blocks used in a PLC ladder logic 6

TON ON Timer

  1. The ON Timer will be switched ON using Input Switch %M0.0. Once the Input switch %M0.0 is turned “ON”. The timer starts and run for the period of specified time and stops. 
  2. During the timer is running the output %Q0.0 will be “OFF”. 
  3. The TON time output coil (Marked in red). It is associated coil of TON Time block. It can be used any number of times in a PLC Ladder Programming for switching “ON” the different Output. The below figure shows one example of such ladder programming.
  4. The %M0.0 is input for the TON time output coil (Since the Timer will not be connected directly to the ladder). 
  5. Some other output %Q0.1 is connected to TON time output relay. Until the TON timer Block “ON” both output will be “OFF”. Once the TON timer goes “OFF” after specified time, both the load goes “ON”.
Understanding Different types of Timer blocks used in a PLC ladder logic 7

TOF OFF Timer

  1. The OFF Timer will be switched ON using Input Switch %M0.1. Once the Input switch %M0.1 is turned “ON”. The timer starts and run for the period of specified time and stops. 
  2. During the timer is running the output %Q0.2 will be “ON”. 
  3. The TOF time output coil (Marked in red). It is associated coil of TOF Time block. It can be used any number of times in a PLC Ladder Programming for switching “ON” the different Output. The below figure shows one example of such Ladder Programming.
  4. The %M0.1 is input for the TOF time output coil (Since the timer will not be connected directly to the Ladder). 
  5. Some other Output %Q0.3 is connected to TOF time output relay. Until the TOF timer Block “ON” both output will be “ON”. Once the TON timer goes “OFF” after specified time, both the load goes “OFF”.
Understanding Different types of Timer blocks used in a PLC ladder logic 8

TONR Timer Accumulator

  1. The TONR Timer will be switched ON using Input Switch %M0.2. Once the Input switch %M0.2 is turned “ON”. The timer starts and run for the period of specified time and stops. 
  2. During the timer is running the output %Q0.4 will be “ON”. 
  3. The TONR time output coil (Marked in red). It is associated coil of TONR Timer block. It can be used any number of times in a PLC Ladder Programming for switching “ON” the different Output. The below figure shows one example of such ladder programming. The TONR timer is similar to TP timer, but the difference is TONR can be switched on only once in PLC ladder programming. It can’t be “ON” even the input %M0.2 Switched “ON” once again.
  4. The %M0.2 is input for the TONR time output coil (Since the Timer will not be connected directly to the Ladder). 
  5. Some other Output %Q0.5 is connected to TONR time output relay. Until the TONR timer Block “ON” both outputs will be “ON”. Once the TONR timer goes “OFF” after specified time, both the load goes “OFF”.
Understanding Different types of Timer blocks used in a PLC ladder logic 9

Following are the instructions for using the SIEMENS TIA site to program ladder logic. (Simulation).

Note: For a detailed explanation of how-to program ladder logic using Siemens TIA Portal, please refer above page.

Simulation screenshots of Different Timer block

TP – Pulse timer

  1. The simulation diagram below shows the status of the timer before the input %M0.0 is switched “ON”. 
Understanding Different types of Timer blocks used in a PLC ladder logic 10
  1. Once the input %M0.0 is switched “ON” the Pulse Timer TP starts running to the specified time period (Say 5s) both the load %Q0.0 and %Q0.1 will be “ON”. After 5s both the load %Q0.0 and %Q0.1 goes “OFF”. Once again both the load %Q0.0 and %Q0.1 will be “ON” only if the TP Timer will be switched “ON”.

(Note: The TP Timer will be turned “OFF” after the specified time period. It will turn once again by triggering Positive Pulse)

Understanding Different types of Timer blocks used in a PLC ladder logic 11

TON – Pulse timer

  1. The simulation diagram below shows the status of the timer before the input %M0.0 is switched “ON”.
Understanding Different types of Timer blocks used in a PLC ladder logic 12
  1. Once the input %M0.0 is switched “ON” the TON timer start run to the specified time period (Say 5s) during the period both the load %Q0.0 and %Q0.1 will be “OFF”.
  2. After TON runs for 5s both the load %Q0.0 and %Q0.1 goes “ON” Continuously until the input switch is OFF. 
Understanding Different types of Timer blocks used in a PLC ladder logic 13

TOF – Pulse timer

  1. The simulation diagram below shows the status of the timer before the input %M0.1 (Usually Normally Closed Coil) is switched “ON”. During the period the load %Q0.0 will be “ON”.
Understanding Different types of Timer blocks used in a PLC ladder logic 14
  1. Once the input %M0.1 is switched “ON” the TOF timer start run to the specified time period (Say 5s) during the period both the load %Q0.0 and %Q0.1 will be “ON”.
  2. After TOF runs for 5s both the load %Q0.0 and %Q0.1 goes “OFF” Continuously until the input switch is ON. 
Understanding Different types of Timer blocks used in a PLC ladder logic 15

TONR – Pulse timer

  • The simulation diagram below shows the status of the timer before the input %M0.2 is switched “ON”. During the period the load %Q0.4 and %Q0.5 both will be “OFF”.
Understanding Different types of Timer blocks used in a PLC ladder logic 16
  • Once the input %M0.2 is switched “ON” the TONR timer start run to the specified time period(Say 5s) during the period both the load %Q0.4 and %Q0.5 will be “OFF”.After the specified time period i.e 5s is completed, the load will be goes to “ON” state. Shown in below figure
Understanding Different types of Timer blocks used in a PLC ladder logic 17
  • But once again if the input switch %M0.2 is Switched “OFF” (Manually). The Load output %Q0.4 and %Q0.5 both loads retain its state it will “ON” continuously. The load accumulates the “ON” period continuously even after the absence of input. Shown in below figure

We were able to develop PLC ladder logic using the exercise mentioned above, and we were also able to simulate and test different types of timer blocks in the ladder logic.

Sundareswaran Iyalunaidu

With over 24 years of dedicated experience, I am a seasoned professional specializing in the commissioning, maintenance, and installation of Electrical, Instrumentation and Control systems. My expertise extends across a spectrum of industries, including Power stations, Oil and Gas, Aluminium, Utilities, Steel and Continuous process industries. Tweet me @sundareshinfohe

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