Programable Logic Controller Basics Explained - automation engineering

Summary

This video explores the automation of mechanical and electrical systems in commercial and industrial settings, focusing on programmable logic controllers (PLCs). Sponsored by TeleControls, it explains how PLCs, acting as small computers, control systems with minimal manual intervention based on pre-programmed outputs and inputs. The video covers the components of PLCs, their basic operation, and advantages, including easier reprogramming and fault-finding. It also provides practical examples of PLC applications in scenarios like airport baggage handling and building temperature control.

Takeaways

• 🏢 Automation of mechanical and electrical systems in commercial and industrial facilities is increasing with the construction of larger, smarter, and more complex buildings.
• 🔗 Telecontrols, a leading manufacturer in the automation industry since 1963, offers technology compatible with all PLCs, HMIs, and controllers, reducing programming time and saving storage space.
• 🤖 PLCs, or Programmable Logic Controllers, are small computers that execute pre-programmed outputs based on inputs and specific rules, with minimal or no manual intervention.
• 🔄 Before PLCs, control was managed by banks of relays which were large, complex, and required physical rewiring to change operations.
• 🔌 PLCs monitor inputs, make decisions based on stored rules, and output commands to automate processes, often in combination with relays for more efficient task handling.
• 🛂 Input modules of PLCs connect to field sensors and perform tasks such as sensing signals, converting signal voltage, isolating fluctuations, and sending corrected signals to the CPU.
• 🧠 The CPU, or Central Processing Unit, is the brain of the PLC, holding the program that decides output requirements by applying rules to input signals.
• 🔩 Output modules interface with field output devices, such as indicator lights, solenoid valves, motor starters, and variable frequency drives, providing signals to control these devices.
• 🔄 Basic PLC operation involves input scanning, program scanning, executing program logic, updating outputs, and housekeeping tasks like self-diagnostics and communication updates.
• 🌡️ Analog inputs, such as those from a thermistor, take longer to process than digital inputs, affecting the scan time which can vary from milliseconds to hundreds of milliseconds depending on the application.
• 🛠️ PLCs offer advantages like local control software storage, software-based connections instead of physical wires, smaller installations, easier reprogramming, and faster fault finding.

Q & A

What is the primary purpose of automation in commercial and industrial facilities?

The primary purpose of automation in commercial and industrial facilities is to control mechanical and electrical systems efficiently, reducing the need for manual intervention and enhancing the operation of larger, smarter, and more complex systems.

Who is Telecontrols and what is their role in the automation industry?

Telecontrols is one of the leading manufacturers in the automation industry since 1963. They produce technology compatible with every PLC, HMI, and controller on the market, which helps reduce PLC programming time and saves storage by handling smaller automation tasks directly.

What does PLC stand for and what is its basic function?

PLC stands for Programmable Logic Controller. Its basic function is to act as a small computer that carries out pre-programmed outputs based on inputs and a set of specific rules, used to control systems with minimal or no manual intervention.

How did control systems operate before the advent of PLCs?

Before PLCs, control systems operated via banks of relays, which controlled dedicated inputs and outputs based on physical wiring. Changing the operation required altering the physical connections, making the system large, complex, and difficult to modify or troubleshoot.

What are the main components of a PLC system?

The main components of a PLC system include input modules, a central processing unit (CPU), output modules, a battery for power failure backup, a user interface, a time clock and calendar, and a power supply for low voltage needs.

How do input modules in a PLC system function?

Input modules in a PLC system sense when a signal is received, convert the signal voltage into the correct format for the CPU, isolate the PLC from fluctuations in input voltage or current, and send the corrected signal to the CPU.

What is the role of the CPU in a PLC system?

The CPU, or central processing unit, is the brain of the PLC system. It holds the program or software that decides what outputs are required by applying rules to the input signals. It typically consists of a microprocessor, a memory chip for storing the program and data, and integrated circuits for communication and other functions.

What is the basic operation process of a PLC?

The basic operation process of a PLC includes an input scan to detect the state of inputs, a program scan to determine actions, execution of program logic, updating outputs to operate devices, and housekeeping for self-diagnostics, communications, and reporting.

What is the advantage of using a PLC over traditional relays in controlling a heating system?

A PLC offers advantages such as the ability to incorporate time functions, easier reprogramming, and the capacity to handle more complex control strategies like PID loops and optimizers. It also simplifies fault finding and allows for more compact installations compared to traditional relays.

Can you provide an example of a complex control strategy mentioned in the script?

An example of a complex control strategy mentioned in the script is the use of an optimizer in heating or cooling systems of commercial buildings. This optimizer learns the building's heating and cooling dynamics over time and starts the system at the optimal time to ensure the building is at the desired temperature when occupied.

What are some of the main advantages of using PLCs in industrial applications?

Some main advantages of using PLCs include local storage of control software for continued operation during system failures, software-based connections reducing the need for physical wiring, smaller installations compared to relay banks, ease of reprogramming, faster fault finding, and the ability to expand inputs and outputs with additional cards.

Outlines

00:00

🤖 Automation in Commercial and Industrial Facilities

The video script introduces the growing reliance on automation for mechanical and electrical systems in commercial and industrial settings, highlighting the role of devices like PLCs (Programmable Logic Controllers). Sponsored by TeleControls, a leading manufacturer in the automation industry since 1963, the script emphasizes the compatibility of TeleControls' technology with various PLCs, HMIs, and controllers, promoting efficiency and ease of use. The video aims to explore how these systems are controlled and the specific devices used for automation, starting with a basic explanation of what a PLC is and its function in controlling systems with minimal manual intervention.

05:00

🔍 Understanding PLCs and Their Evolution

This paragraph delves into the history and functionality of PLCs, explaining their evolution from complex relay systems to modern, software-logic controlled devices. It describes how PLCs, which are essentially small computers, automate processes based on pre-programmed outputs determined by inputs and specific rules. The script contrasts the old method of using physical relays with the current software-based approach, illustrating the advantages of PLCs in terms of ease of reprogramming and fault-finding. The paragraph also explains the basic components of a PLC system, including input modules, the CPU, output modules, and additional features like a battery for power failure protection and a user interface for configuration.

10:02

🔧 The Working Mechanism of PLCs and Practical Examples

The script provides an in-depth look at the operational stages of a PLC, from input scanning to program execution and output updating. It uses practical examples to illustrate how PLCs can be applied in various scenarios, such as controlling a boiler based on room temperature or managing a heating system in a commercial building. The paragraph explains how analog inputs, like a thermistor, and actuators, like a valve, can be integrated into a PLC system for precise control. It also introduces the concept of a PID control loop for temperature regulation and discusses more complex systems that use optimizers to learn and predict the best times to activate heating or cooling systems for energy efficiency.

15:03

🚀 Advantages of PLCs and Continuing Education

The final paragraph of the script outlines the advantages of using PLCs, such as local storage of control software, ease of reprogramming, and improved fault-finding. It also touches on the modular nature of PLC systems, allowing for easy expansion of inputs and outputs. The script concludes by encouraging viewers to continue their education on controls and electrical engineering through suggested videos and to follow the sponsor's social media channels for more information.

Keywords

💡Automation

Automation refers to the use of control systems and information technologies to reduce the need for human intervention in the operation of mechanical and electrical systems. In the context of the video, automation is crucial for managing complex systems in commercial and industrial facilities, making processes more efficient and reliable. The script mentions the increasing reliance on automation as systems become larger and more complex.

💡Telecontrols

Telecontrols is identified as a leading manufacturer in the automation industry since 1963. The company's technology is highlighted for its compatibility with various PLCs, HMIs, and controllers, which is significant for reducing programming time and storage usage in automation tasks. The video is sponsored by Telecontrols, emphasizing their role in the industry.

💡PLC (Programmable Logic Controller)

A PLC is a specialized computer used in industrial environments to control machinery and processes based on inputs and a set of rules. The video explains that PLCs have largely replaced traditional relay systems due to their flexibility and ability to be reprogrammed without the need for physical rewiring. PLCs are central to the video's theme of modern automation techniques.

💡HMI (Human-Machine Interface)

HMI refers to the interface that allows humans to interact with a machine or process, typically through a screen and controls. Although not explicitly detailed in the script, the mention of HMI alongside PLCs suggests its importance in the automation process, providing a way to monitor and control systems.

💡Relay

A relay is an electrical switch that is operated by an electromagnet. Historically, relays were used to control circuits in industrial applications. The video script contrasts the old method of using banks of relays with the modern use of PLCs, illustrating the evolution of automation technology.

💡Input Modules

Input modules are components of a PLC that connect to field sensors and convert the sensor signals into a format that the PLC can process. The script describes various types of digital and analog inputs, emphasizing the role of input modules in translating real-world conditions into data for the PLC to act upon.

💡CPU (Central Processing Unit)

The CPU of a PLC is its 'brain,' executing the logic program based on input signals. The script explains that the CPU processes the inputs, applies the programmed rules, and determines the necessary outputs, which is fundamental to the operation of automated systems.

💡Output Modules

Output modules in a PLC are responsible for sending signals to control devices such as indicator lights, valves, and motors. The video script mentions output modules in the context of how a PLC communicates with the physical world to enact changes based on its programming.

💡PID Control Loop

A PID control loop, standing for Proportional-Integral-Derivative, is a common method of controlling processes in automation. The script uses a heating system example to illustrate how a PID loop can manage the opening of a valve to maintain a desired room temperature, demonstrating a more advanced application of PLCs.

💡Optimization

Optimization in the context of the video refers to the strategy of starting heating or cooling systems at the most efficient times to meet occupancy needs. The script describes an optimizer as a learning system that adjusts operation times based on the building's thermal dynamics, showcasing a sophisticated use of PLCs.

💡Duty and Standby Configuration

This term refers to a setup where one device operates while another is on standby, ready to take over if needed. The script uses pumps in a heating system as an example, explaining how a PLC can manage which pump is active based on run hours, ensuring reliability and longevity of the system.

Highlights

The increasing reliance on automation of mechanical and electrical systems in commercial and industrial facilities.

Telecontrols, a leading manufacturer in the automation industry since 1963, is sponsoring the video.

Telecontrols' technology is compatible with every PLC, HMI, and controller on the market, reducing programming time and storage usage.

PLCs, or programmable logic controllers, are small computers that automate systems with minimal manual intervention.

Pre-PLC control systems used banks of relays, which were vast, complex, and difficult to change or troubleshoot.

PLCs can handle both simple on/off control and more sophisticated responses based on calculations, sequences, and logic.

Relays are often used in combination with PLCs to handle automation tasks and reduce PLC programming requirements.

Input modules of field sensors are the physical connections between the outside world and the PLC.

The CPU, or central processing unit, is the brain of the PLC, holding the program that decides what outputs are required.

Output modules provide the signal to control devices such as indicator lights, solenoid valves, and motor starters.

PLCs perform a pre-programmed output depending on the input signal by following a set of rules.

The basic operation of a PLC includes input scanning, program scanning, executing logic, updating outputs, and housekeeping.

Analog inputs, like those from a thermistor, take longer to process than simple digital on/off inputs.

PLCs can incorporate time functions to control when devices like boilers should turn on or off.

PID control loops are used for more sophisticated temperature control, gradually adjusting valve positions.

Optimizers in commercial buildings learn and control heating or cooling systems to maintain optimal temperatures.

PLCs offer advantages such as local control software storage, easier reprogramming, and simplified fault-finding.

The video provides educational content on controls and electrical engineering for further learning.

Transcripts

[Applause]

[Music]

almost every commercial building

an industrial facility relies on the

automation

of their mechanical and electrical

systems this trend is only set to

increase

especially as larger smarter more

complex systems

and buildings are constantly under

construction

so how do we control these systems and

what devices are used to achieve that

that's what we'll be covering in this

video which is sponsored by telecontrols

tele controls are one of the leading

manufacturers in the automation industry

since 1963. their technology is

compatible with every plc

hmi and controller on the market which

reduces plc

programming time and saves valuable

storage by dealing directly

with smaller automation tasks click the

link in the video description down below

to learn how teles products can make the

best of your plc application

you can contact them at sales at

telecontrols.com

or even via linkedin

plc stands for programmable logic

controller

there are many variations but they

typically look something like this

a programmable logic controller is

basically a small computer

that can carry out pre-programmed

outputs based on inputs

and a set of specific rules they are

used in commercial

and industrial applications to control

systems

with minimal and sometimes even zero

manual intervention

the operation can be a simple on off

control

based on the status of the input or a

more sophisticated response

based on calculations sequence and logic

before plcs control was carried out

via banks of relays each relay

controlled

dedicated inputs and outputs based on

physical wiring

relays would control other relays to

form logic controllers

for example with a simple and gate only

when

two inputs are energized this one and

this one

does the relay output energize these

inputs could be sensors

or they could be outputs from other

relays

to change the operation the physical

wiring had to be changed

so the physical connections had to be

altered if a different response was ever

required

these old banks of relays were vast in

size and very complex

this is an example of an elevator relay

bank

and this is the relay bank from an old

electrical substation

as you can imagine these are not going

to be easy to change

and finding faults can be difficult and

very time consuming

with the invention of solid state

electronics and microchips

the command logic part of the banks of

relays could be replaced with software

logic

and so plcs quickly took over plcs vary

widely on their application

but they all monitor their inputs they

make a decision

based on a stored set of rules and from

those

they then output commands to automate a

process

we often find relays used in combination

with plcs

the relays can directly deal with

automation tasks

and communicate with the plc this will

reduce the amount of programming

required on the plc

and also free up storage space plcs are

widely used

for example when you check a bag in at

the airport

the bag is given a barcode and it enters

the conveyor belt

a plc scans the barcode and based on a

set of rules

decides if the bag is diverted to either

the domestic

or international route the next plc

scans the barcode and decides which city

the bag needs to be diverted to

the next plc decides which gate it also

needs to be diverted to

and if all of this goes to plan then the

bag will arrive at the correct gate

first we have the input modules of field

sensors these are the physical

connections

between the outside world and the plc

these can be digital inputs such as

simple on off switches

biometallic temperature strips presence

or motion sensors

or even a float switch these digital

inputs

can only provide information on whether

something is either on

or off and nothing in between for that

we would need an analog input for

example a

simple control knob which ranges from

zero to one hundred percent

this will go through a voltage

transformer to give zero volts

at zero percent and ten volts at one

hundred percent

the plc can scale the input to match the

sensitivity required

for very accurate output control it

could

also convert the voltage into current

using resistors and ohm's law

the amount of current usually measured

in milliamps

tells the plc whether something is

performing between

on and off these inputs could be for

example

a thermocouple or a resistance

temperature detector

it could be a pressure sensor or perhaps

a strain gauge

these voltages or currents are converted

into a digital equivalent number

that can be understood by the cpu we

will look at that a little later in this

video

input modules will perform four main

tasks

they sense when a signal is received

they convert the signal voltage

into the correct signal for the cpu they

isolate the plc

from fluctuations in the input voltage

or current signal

and they send the corrected signal to

the cpu

the cpu or central processing unit

is the brains of the operation it holds

the program

or software that decides what outputs

are required

by applying rules to the input signals

the cpu

typically consists of a microprocessor

which does the work based on the input

value and the logic in the program

a memory chip to store the program this

will also store the output history any

faults or alarms

etc then we also have other integrated

circuits

these can be things such as modbus and

lan connections

which allow us to remotely communicate

with reprogram

or even monitor the device then there's

the output modules

or field output devices this is

providing the signal to the device we

are controlling

for example a simple indicator light a

solenoid valve

a motor starter a variable frequency

drive

etc there are some other parts such as a

battery

to keep the plc alive in the event of a

power failure

there might be a small screen for a user

interface to allow some configuration

there will need to be a time clock and

calendar to operate a device at the

correct time

and there will also need to be a power

supply to provide the low voltage used

by the cpu

as well as the input and output modules

by the way

we have covered variable frequency

drives motor starters and solenoid

valves

in detail in our previous videos do

check those out

links can be found in the video

description down below

the basic operation of a plc is to

perform a pre-programmed

output depending on the input signal by

following a set of rules

the plc completes the following stages

in its basic operation

first there is the input scan which

detects the state of the inputs

then the program scan to see what needs

to be done

then it will execute the program logic

to actually implement

what the rules state then it must update

the outputs

to operate output devices based on the

program requirements

finally the housekeeping for

self-diagnostics

communications updates and reporting the

scan time

which is the time it takes to complete

all the stages

depends on the sensitivity the

resilience

and system processing time analog inputs

tend to take longer to process compared

to more simple

digital on off inputs for example

a water tank might have a very fast scan

time

of 2 milliseconds and this will prevent

overfilling

but a room temperature control can be

much slower

perhaps 100 milliseconds let's see an

example of a simple

response we have a bi-metallic strip

temperature sensor

a plc and a boiler the biometallic strip

bends as it becomes hot and cold so we

can use this

to detect if the room is at the desired

temperature

and from this control the boiler when

the room is at the correct temperature

the circuit is complete and the plc

receives a signal so the boiler is

off when the room temperature drops the

circuit is no longer complete

and the plc detects its change on the

input

it reacts by sending an output signal to

turn the boiler on

this is very simple and we could also

use a simple relay to achieve this

however a plc is better because

it has a time function so it can check

the time before switching on the boiler

for example the building might be empty

at nights and on weekends

so we don't want the boiler to turn on

them the plc

is told the room is too cold it checks

the time and date

to see if it's allowed to turn on and

then

based on this decides whether to turn

the boiler on

or leave it off we can then add extra

functions and inputs

for example a motion sensor on the input

the thermostat tells the plc the room is

too cold

the plc will check the time to ensure it

is allowed to turn the boiler on

and now it can also check to see if the

room is occupied

for example there could be a public

holiday that isn't listed on the

calendar

the building is empty so the boiler

doesn't need to turn on

in this next more sophisticated example

we have

a thermistor a plc as well as an

actuator valve

the thermistor can provide a temperature

scale rather than

a simple on off input like the

biometallic strip

the actuator valve can open anywhere

between zero and one hundred percent

to control how much hot water is

provided to heat the room

for this we would use a pid control loop

which stands for proportional integral

and derivative control

we won't go into too much detail on pids

but essentially this will control the

valve position

to ensure it only opens enough to suit

the difference

between the room's desired temperature

and the room's actual temperature

for example if the room temperature

dropped very slightly

we don't want the heating valve to

instantly open 100

because the room will heat too quickly

and this will overshoot the desired

temperature

at this point it will then instantly

turn off and the cycle will repeat

instead we want the valve to gradually

open in proportion to the demand

so if there is a small temperature

difference the valve slowly opens

a small amount if there is a large

temperature

difference the valve opens further and

faster

it then decreases as it approaches the

desired temperature

until the valve finds the perfect

position to maintain

the desired room temperature let's see

a more complex example in many

commercial buildings

the heating or cooling system will use a

control strategy

known as an optimizer this learns over a

period of time

how quickly the building heats up and

cools down

it then starts the heating or cooling

system at the optimal time

before the building will be occupied for

example

if the staff are due to turn up and

start work at 9am

the heating system knows that it will

need to turn on

at 7am to ensure that the rooms are all

at the correct temperature

let's say this system has a plc with the

optimizer software installed

this controls an actuator valve for the

heating system

this system also has two pumps which are

set up

in duty and standby configuration so

only one pump

runs at a time the plc will decide

which pump to turn on based on whichever

has the lowest number of previous run

hours

the plc will monitor a flow sensor to

detect if the pump turns on

when told to do so if the pump fails to

turn

on the plc receives an alarm and it will

cut the power

it then tells the other pump to start

however

before the heating system and pump start

the plc will check with the clock

should the heating turn on today and if

so

at what time will the building be

occupied

the clock says yes the scheduled

occupancy time

is 9 am the plc then checks the current

temperature of the room

and calculates the difference between

this and the desired temperature

it then checks the outdoor temperature

to calculate how long it will take to

heat the building

because on a very cold day there will be

a greater heat loss

and so this will take longer from this

the plc calculates

what time it needs to turn the heating

system on

so that the building is at the desired

temperature

ready for 9 am by the way we have

covered duty and standby pumps and

relays in our previous video

do check that out links can be found in

the video description down below

there are many advantages of plcs but

some of the main ones are as follows

the control software is stored locally

so

in the event of a building energy

management system failure

the plc can carry on working the

connections between the plc inputs and

outputs

are made by the software and not by lots

of physical wires plc

installations are smaller than hard

wired relay banks

but they can still use relays when

needed

plc's are much easier to reprogram fault

finding is easier

and faster you can load the same program

onto multiple plc units to save time

you can also expand the inputs and

outputs with more cards

okay that's it for this video but to

continue learning about controls and

electrical engineering

check out one of the videos on screen

now and i'll catch you there for the

next lesson

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