Allen Bradley PLC Timer EN with TON

This blog post will cover how to use the Timer EN function with TON in Allen Bradley PLCs. We’ll discuss the basics of timers, the TON instruction, and how to implement it in your PLC programs.

What are Timers in PLC?

Timers are essential components in PLC programming, allowing you to control the duration of events. They work by measuring the time elapsed since a trigger condition is met. Once the time reaches a predetermined value, the timer’s output changes state, which can then be used to trigger other actions within your program.

The TON Instruction

The TON (Timer On Delay) instruction is one of the most common timer functions used in Allen Bradley PLCs. It provides a simple way to create a timer that starts counting when a trigger input is turned ON and continues counting until the preset time is reached.

TON Instruction Parameters

The TON instruction has the following parameters:

• EN (Enable): This input turns the timer ON and starts the counting process. When EN is OFF, the timer stops counting.
• PRE (Preset): This parameter sets the desired time delay in milliseconds, seconds, or minutes, depending on the PLC’s configuration.
• TT (Timer Time): This output displays the current time value of the timer. It’s useful for monitoring the timer’s progress.
• DN (Done): This output turns ON when the timer reaches the preset time. It indicates that the timer has completed its cycle.

Implementing the TON Instruction

Here’s a step-by-step guide on how to implement the TON instruction in your Allen Bradley PLC program:

1. Add the TON instruction to your program: Open the program in your PLC software (such as RSLogix 5000) and add the TON instruction to the desired location.
2. Configure the parameters: Set the EN, PRE, and other parameters according to your application’s requirements. Ensure the time units are consistent with your program.
3. Connect the inputs and outputs: Connect the EN input to the trigger signal that will start the timer. Connect the DN output to the action you want to initiate when the timer reaches the preset time.
4. Monitor the timer: You can monitor the timer’s progress by observing the TT output. This will show you the elapsed time.

Practical Example: Using TON for a Motor Start Delay

Let’s say you want to create a program that starts a motor with a 5-second delay. Here’s how you can implement it using the TON instruction:

1. Add a TON instruction: Add a TON instruction to your program and name it “MotorStartDelay”.
2. Set the parameters: Set the EN input to a start button, the PRE to 5 seconds, and the DN output to the motor’s start bit.
3. Connect the inputs and outputs: Connect the start button’s output to the EN input of the TON instruction. Connect the DN output to the motor’s start bit.
4. Run the program: When the start button is pressed, the TON instruction will start counting. After 5 seconds, the DN output will turn ON, which will then start the motor.

Conclusion

The TON instruction is a powerful tool for implementing time-based logic in Allen Bradley PLCs. By understanding its parameters and implementation steps, you can effectively use it to control the duration of events and create sophisticated PLC programs.

Remember to always test your programs thoroughly to ensure they function correctly and meet your application’s requirements.