🔵✅TEMPORIZADORES EN LADDER (TON-TOF-TP)

Name: 🔵✅TEMPORIZADORES EN LADDER (TON-TOF-TP)
Uploaded: 2021-06-14T22:56:48.000Z
Duration: 50 min 56 s

Introduction to Timers in PLC Programming

Overview of Timer Concepts

The video introduces the topic of timers as part of a basic course on PLC programming, specifically focusing on IEC 61131 standards.

It outlines three main types of timers and mentions some variants found in different programming environments.

Practical Application

An example is provided using a Raspberry Pi programmed as a PLC, demonstrating how timers can activate or deactivate coils or memory based on specified time intervals.

A simple representation shows how pressing a button starts a timer that counts for three seconds before activating a motor.

Types of Timers According to IEC Standards

Timer Categories

The video identifies three types of timers defined by the IEC 61131 standard: TON (On Delay), TOF (Off Delay), and TP (Pulse Timer).

Each timer has two inputs (IN and PT) and two outputs (Q7), differing primarily in their operational characteristics.

Variants Across Programming Environments

Different programming environments like Studio 5000 and TIA Portal are discussed, highlighting similar functionalities but with unique representations.

The GRT timer from Studio 5000 is noted for its retentive feature, which retains accumulated time even when deactivated.

Detailed Explanation of TON Timer Functionality

Operation Mechanics

The TON timer delays the activation of an output coil for a predetermined duration after detecting a rising edge signal at its input.

When the input signal transitions from low to high, the timer begins counting until it reaches the preset time (PT).

Output Behavior

Once the elapsed time equals PT, the output activates; however, if the input drops back to zero before reaching PT, both output and elapsed time reset to zero.

Understanding Timer Operations in Motor Control

Activation and Timing Mechanism

The output of the system activates when the input is at 1, remaining active until the input drops to 0, which resets the elapsed time.

An example illustrates how to implement a delay for ignition using a timer (TON), requiring an engine interlock.

The setup includes start/stop controls and utilizes a TON timer, with syntax indicating a direct time value of 5 seconds.

Timer Functionality and Interlocking

A coil named "be delay start" is added; it energizes after 5 seconds once the start signal is triggered.

Alternatively, variables can be used instead of creating coils; these are defined as TON type variables within the program.

Accessing signals from timers involves writing variable names followed by ".CV" to retrieve current values.

Output Behavior Based on Input Signals

Initially, if the start button is pressed but not held for 5 seconds, no output activation occurs; interlocking only happens after reaching this threshold.

Once 5 seconds elapse with continuous pressing of the start button, energy flows through and successful interlocking occurs.

If the button is released before reaching 5 seconds, both output and elapsed time reset immediately.

Timer Resetting Dynamics

The timer restarts if input does not maintain its state for the required duration (5 seconds).

A descending edge triggers timer operation; without an initial input of 1, timing does not commence.

Distinction Between Rising and Falling Edges

With a falling edge detected at input transition from high to low (1 to 0), timing begins while outputs remain off initially.

When elapsed time meets predetermined conditions during counting phases, outputs toggle states based on input changes.

Practical Application: Pressure Monitoring Example

An exercise demonstrates adding a timer to trigger an alarm upon detecting pressure drops lasting at least 4 seconds in machinery operations.

Understanding Pressure Drop Alarms in Equipment

Normal Behavior of Pressure Variations

The simultaneous operation of brakes and pneumatic elements often leads to varying pressure levels, which is considered a normal behavior.

An alarm system is implemented to monitor pressure drops; if the drop lasts longer than four seconds, an alarm is triggered.

Alarm Activation Logic

When the pressure exceeds 100 psi, a signal activates a timer that resets when the pressure remains stable.

If the pressure drop does not exceed four seconds, no alarm is generated; this prevents unnecessary alerts during brief fluctuations.

Timer Functionality and Alarm System

The system only triggers an alarm if the pressure drop persists beyond four seconds, ensuring efficient monitoring.

Upon recovery of pressure, the output signal reactivates, allowing for potential equipment restart based on user preference.

Pulse Timer Mechanism

A pulse timer starts counting upon receiving a pulse input; it maintains its output until reaching a predetermined time without resetting for additional pulses.

The elapsed time continues counting even with fluctuating signals until it meets the target duration.

Practical Application Example

In mixing equipment scenarios, pressing the start button initiates motor operation for ten uninterrupted seconds using a timer setup.

Multiple presses of the start button do not interrupt motor function or reset timing; this ensures consistent operation as intended.

Programming Best Practices

Timer Variables and Programming Practices

Analyzing Timer Functionality

The discussion begins with an analysis of two timers that did not function as intended when counted to eight, indicating a need for further adjustments.

It is suggested that different variables should be created for each timer to enhance functionality, specifically mentioning the need for timers below zero and below one.

Implementing Timer Logic

The speaker emphasizes the importance of starting both timers correctly, with one counting up to eight and another counting up to ten seconds.

The activation of these timers is demonstrated, showcasing best programming practices in action during the explanation.