Chapter 7, Problem 13P

Program Plan Intro

Timer:

• Timer is mainly used to keep an output ON for a specific length of time.
• It provides a preset delay to the control actions.
• In a timer, the output will be energized when the preset value becomes equal to the accumulated value.
• Three different types of timers include a Delay-OFF, a Delay-ON, and a Delay-ON-Retentive timer.

Timer OFF Delay (TOF):

• TOF refers to an off-delay timer.
• TOF counts the time-based intervals as soon as the instruction becomes false.
• Here, the output changes its state from high to low when the timer provides some time delay (instruction goes from ON to OFF state).

Given:

In the given figure, the tags are formed for various areas of controller for various purposes.

• The two push buttons are used to start and stop the process.
• The highest level of the tank is indicated by the full level sensor switch. Here, when the tank level is full, the switch gets closed.
• The empty level of the tank is indicated by the empty level sensor switch. Here, when the tank starts the filling process, the switch gets closed.
• The “Solenoid A” is used to de-energize (it means to fill) the tank.
• The “Solenoid B” is used to energize (it means to empty) the tank.