Timers And Counters In PLCs
Sample Solution
Timers in Allen Bradley and Siemens PLCs
Timers as Logical Devices
Timers are logical devices that are used to delay an action for a specified amount of time. They are commonly used in PLCs to control processes that require precise timing, such as conveyor belts, pumps, and valves.
In its simplest form, a timer can be thought of as a switch that is controlled by a clock. When the timer is activated, the clock starts to run. When the clock reaches the preset time, the timer turns on and the switch closes. The switch can be used to control a variety of devices, such as a motor, a solenoid, or a relay.
Full Answer Section
Timer Instructions in Studio 5000
Studio 5000 is the programming software for Allen Bradley PLCs. It includes a variety of timer instructions that can be used to implement different types of timers. The most common timer instructions in Studio 5000 are:
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TON (Timer On): This instruction turns on the timer output when the timer input is activated and keeps it on until the preset time has elapsed.
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TOF (Timer Off): This instruction turns on the timer output when the preset time has elapsed and keeps it on until the timer input is deactivated.
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TINT (Timer Interval): This instruction turns on the timer output for a specified interval of time, regardless of the state of the timer input.
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TTO (Timer One-Shot): This instruction turns on the timer output for a specified interval of time, but only once.
Types of Timers in Studio 5000
Studio 5000 supports two types of timers:
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Standard timers: Standard timers are used for most applications. They are easy to use and have a wide range of preset times.
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Extended timers: Extended timers are used for applications that require more precision. They have a higher resolution and can be used for longer delays.
Input and Output Signals for Timers
Timers have two main signals:
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Input signal: The input signal is used to control the timer. When the input signal is activated, the timer starts to run.
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Output signal: The output signal is used to indicate the state of the timer. When the output signal is on, the timer is active and the switch is closed.
Differences Between Allen Bradley and Siemens Timers
There are a few key differences between Allen Bradley and Siemens timers. These differences include:
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Preset time resolution: Allen Bradley timers have a preset time resolution of 0.01 seconds, while Siemens timers have a preset time resolution of 0.1 seconds.
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Reset behavior: Allen Bradley timers are automatically reset when the timer input is deactivated, while Siemens timers must be explicitly reset.
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Time base: Allen Bradley timers can use a variety of time bases, including the CPU clock, while Siemens timers only use the CPU clock.
Conclusion
Timers are an important part of any PLC system. They are used to control a wide variety of processes and are essential for precise timing applications. In this discussion, we have looked at the architecture of timers, how they are implemented in Studio 5000, and the different types of timers that are available. We have also looked at the differences between Allen Bradley and Siemens timers.