HOW TO START AUTOMATION

Response Time Concerns

Response Time Concerns

Now that we know about response time, here's what it really means to the application. The PLC can only see an input turn on/off when it's looking. In other words, it only looks at its inputs during the check input status part of the scan.

In the diagram, input 1 is not seen until scan 2. This is because when input 1 turned on, scan 1 had already finished looking at the inputs.
Input 2 is not seen until scan 3. This is also because when the input turned on scan 2 had already finished looking at the inputs.
Input 3 is never seen. This is because when scan 3 was looking at the inputs, signal 3 was not on yet. It turns off before scan 4 looks at the inputs. Therefore signal 3 is never seen by the plc.

To avoid this we say that the input should be on for at least 1 input delay time + one scan time.

But what if it was not possible for the input to be on this long? Then the plc doesn't see the input turn on. Therefore it becomes a paper weight! Not true... of course there must be a way to get around this. Actually there are 2 ways.

Pulse stretch function. This function extends the length of the input signal until the plc looks at the inputs during the next scan.( i.e. it stretches the duration of the pulse.)

Interrupt function. This function interrupts the scan to process a special routine that you have written. i.e. As soon as the input turns on, regardless of where the scan currently is, the plc immediately stops what its doing and executes an interrupt routine. (A routine can be thought of as a mini program outside of the main program.) After its done executing the interrupt routine, it goes back to the point it left off at and continues on with the normal scan process.

Now let's consider the longest time for an output to actually turn on. Let's assume that when a switch turns on we need to turn on a load connected to the plc output.
The diagram below shows the longest delay (worst case because the input is not seen until scan 2) for the output to turn on after the input has turned on.
The maximum delay is thus 2 scan cycles - 1 input delay time.

The Program Scan

The Program Scan

Let's watch what happens in this program scan by scan.

Initially the tank is empty. Therefore, input 0000 is TRUE and input 0001 is also TRUE.

Scan 1

Scan 2-100

Gradually the tank fills because 500(fill motor) is on.
After 100 scans the oil level rises above the low level sensor and it becomes open. (i.e. FALSE)

 Scan 101-1000

Notice that even when the low level sensor is false there is still a path of true logic from left to right. This is why we used an internal relay. Relay 1000 is latching the output (500) on. It will stay this way until there is no true logic path from left to right.(i.e. when 0001 becomes false)
After 1000 scans the oil level rises above the high level sensor at it also becomes open (i.e. false)

Scan 1001

Scan 1002

Since there is no more true logic path, output 500 is no longer energized (true) and therefore the motor turns off.
After 1050 scans the oil level falls below the high level sensor and it will become true again.

Scan 1050

Notice that even though the high level sensor became true there still is NO continuous true logic path and therefore coil 1000 remains false!
After 2000 scans the oil level falls below the low level sensor and it will also become true again. At this point the logic will appear the same as SCAN 1 above and the logic will repeat as illustrated above.

Response Time

 Response Time

The total response time of the PLC is a fact we have to consider when shopping for a PLC. Just like our brains, the PLC takes a certain amount of time to react to changes. In many applications speed is not a concern, in others though...
If you take a moment to look away from this text you might see a picture on the wall. Your eyes actually see the picture before your brain says "Oh, there's a picture on the wall". In this example your eyes can be considered the sensor. The eyes are connected to the input circuit of your brain. The input circuit of your brain takes a certain amount of time to realize that your eyes saw something. (If you have been drinking alcohol this input response time would be longer!) Eventually your brain realizes that the eyes have seen something and it processes the data. It then sends an output signal to your mouth. Your mouth receives this data and begins to respond to it. Eventually your mouth utters the words "Gee, that's a really ugly picture!".

PLC Operation

PLC Operation

A PLC works by continually scanning a program. We can think of this scan cycle as consisting of 3 important steps. There are typically more than 3 but we can focus on the important parts and not worry about the others. Typically the others are checking the system and updating the current internal counter and timer values.

Step 1-CHECK INPUT STATUS-First the PLC takes a look at each input to determine if it is on or off. In other words, is the sensor connected to the first input on? How about the second input? How about the third... It records this data into its memory to be used during the next step.
Step 2-EXECUTE PROGRAM-Next the PLC executes your program one instruction at a time. Maybe your program said that if the first input was on then it should turn on the first output. Since it already knows which inputs are on/off from the previous step it will be able to decide whether the first output should be turned on based on the state of the first input. It will store the execution results for use later during the next step.
Step 3-UPDATE OUTPUT STATUS-Finally the PLC updates the status of the outputs. It updates the outputs based on which inputs were on during the first step and the results of executing your program during the second step. Based on the example in step 2 it would now turn on the first output because the first input was on and your program said to turn on the first output when this condition is true.
After the third step the PLC goes back to step one and repeats the steps continuously. One scan time is defined as the time it takes to execute the 3 steps listed above.

Basic Instructions

Basic Instructions

Now let's examine some of the basic instructions is greater detail to see more about what each one does.

Load                     A LoaD (contact) symbol
The load (LD) instruction is a normally open contact. It is sometimes also called examine if on.(XIO) (as in examine the input to see if its physically on) The symbol for a load instruction is shown below.
This is used when an input signal is needed to be present for the symbol to turn on. When the physical input is on we can say that the instruction is True. We examine the input for an on signal. If the input is physically on then the symbol is on. An on condition is also referred to as a logic 1 state.
This symbol normally can be used for internal inputs, external inputs and external output contacts. Remember that internal relays don't physically exist. They are simulated (software) relays. 

LoadBar                         A LoaDNot (normally closed contact) symbol
The LoaDBar instruction is a normally closed contact. It is sometimes also called LoaDNot or examine if closed. (XIC) (as in examine the input to see if its physically closed) The symbol for a loadbar instruction is shown below.
This is used when an input signal does not need to be present for the symbol to turn on. When the physical input is off we can say that the instruction is True. We examine the input for an off signal. If the input is physically off then the symbol is on. An off condition is also referred to as a logic 0 state.
This symbol normally can be used for internal inputs, external inputs and sometimes, external output contacts. Remember again that internal relays don't physically exist. They are simulated (software) relays. It is the exact opposite of the Load instruction.
*NOTE- With most PLCs this instruction (Load or Loadbar) MUST be the first symbol on the left of the ladder.

Logic State	Load	LoadBar
0	False	True
1	True	False

Out                                   An OUT (coil) symbol
The Out instruction is sometimes also called an OutputEnergize instruction. The output instruction is like a relay coil. Its symbol looks as shown below.
When there is a path of True instructions preceding this on the ladder rung, it will also be True. When the instruction is True it is physically On. We can think of this instruction as a normally open output. This instruction can be used for internal coils and external outputs.

Outbar                          An OUTBar (normally closed coil) symbol
The Outbar instruction is sometimes also called an OutNot instruction. Some vendors don't have this instruction. The outbar instruction is like a normally closed relay coil. Its symbol looks like that shown below.
When there is a path of False instructions preceding this on the ladder rung, it will be True. When the instruction is True it is physically On. We can think of this instruction as a normally closed output. This instruction can be used for internal coils and external outputs. It is the exact opposite of the Out instruction.

Logic State	Out	OutBar
0	False	True
1	True	False

What is a PLC?

What is a PLC?

A PLC (i.e. Programmable Logic Controller) is a device that was invented to replace the necessary sequential relay circuits for machine control. The PLC works by looking at its inputs and depending upon their state, turning on/off its outputs. The user enters a program, usually via software, that gives the desired results.
PLCs are used in many "real world" applications. If there is industry present, chances are good that there is a plc present. If you are involved in machining, packaging, material handling, automated assembly or countless other industries you are probably already using them. If you are not, you are wasting money and time. Almost any application that needs some type of electrical control has a need for a plc.
For example, let's assume that when a switch turns on we want to turn a solenoid on for 5 seconds and then turn it off regardless of how long the switch is on for. We can do this with a simple external timer. But what if the process included 10 switches and solenoids? We would need 10 external timers. What if the process also needed to count how many times the switches individually turned on? We need a lot of external counters.
As you can see the bigger the process the more of a need we have for a PLC. We can simply program the PLC to count its inputs and turn the solenoids on for the specified time.
This site gives you enough information to be able to write programs far more complicated than the simple one above. We will take a look at what is considered to be the "top 20" plc instructions. It can be safely estimated that with a firm understanding of these instructions one can solve more than 80% of the applications in existence.
That's right, more than 80%! Of course we'll learn more than just these instructions to help you solve almost ALL your potential plc applications.

BASIC PLC PROGRAMMING

BASIC PLC PROGRAMMING

History OF THE PLC

In the late 1960's PLCs were first introduced. The primary reason for designing such a device was eliminating the large cost involved in replacing the complicated relay based machine control systems. Bedford Associates (Bedford, MA) proposed something called a Modular Digital Controller (MODICON) to a major US car manufacturer. Other companies at the time proposed computer based schemes, one of which was based upon the PDP-8. The MODICON 084 brought the world's first PLC into commercial production.
When production requirements changed so did the control system. This becomes very expensive when the change is frequent. Since relays are mechanical devices they also have a limited lifetime which required strict adhesion to maintenance schedules. Troubleshooting was also quite tedious when so many relays are involved. Now picture a machine control panel that included many, possibly hundreds or thousands, of individual relays. The size could be mind boggling. How about the complicated initial wiring of so many individual devices! These relays would be individually wired together in a manner that would yield the desired outcome. Were there problems? You bet!
These "new controllers" also had to be easily programmed by maintenance and plant engineers. The lifetime had to be long and programming changes easily performed. They also had to survive the harsh industrial environment. That's a lot to ask! The answers were to use a programming technique most people were already familiar with and replace mechanical parts with solid-state ones.
In the mid70's the dominant PLC technologies were sequencer state-machines and the bit-slice based CPU. The AMD 2901 and 2903 were quite popular in Modicon and A-B PLCs. Conventional microprocessors lacked the power to quickly solve PLC logic in all but the smallest PLCs. As conventional microprocessors evolved, larger and larger PLCs were being based upon them. However, even today some are still based upon the 2903.(ref A-B's PLC-3) Modicon has yet to build a faster PLC than their 984A/B/X which was based upon the 2901.
Communications abilities began to appear in approximately 1973. The first such system was Modicon's Modbus. The PLC could now talk to other PLCs and they could be far away from the actual machine they were controlling. They could also now be used to send and receive varying voltages to allow them to enter the analog world. Unfortunately, the lack of standardization coupled with continually changing technology has made PLC communications a nightmare of incompatible protocols and physical networks. Still, it was a great decade for the PLC!
The 80's saw an attempt to standardize communications with General Motor's manufacturing automation protocol(MAP). It was also a time for reducing the size of the PLC and making them software programmable through symbolic programming on personal computers instead of dedicated programming terminals or handheld programmers. Today the world's smallest PLC is about the size of a single control relay!
The 90's have seen a gradual reduction in the introduction of new protocols, and the modernization of the physical layers of some of the more popular protocols that survived the 1980's. The latest standard (IEC 1131-3) has tried to merge plc programming languages under one international standard. We now have PLCs that are programmable in function block diagrams, instruction lists, C and structured text all at the same time! PC's are also being used to replace PLCs in some applications. The original company who commissioned the MODICON 084 has actually switched to a PC based control system.

Manufacturing Execution Systems

In response to the growing demands of today's complex, global economy, successful manufacturing is dependent upon the unification of business and plant floor systems.

Factory Automation Systems provides the control systems layer of the manufacturing process. We also provide the information flow to instruct the people and machines on the activities and tasks needed to make product to a given requirement, the Manufacturing Execution Layer.

·       Resource allocation and status

·       Operations/detail scheduling

·       Dispatching production units

·       Document control

·       Data collection/acquisition

·       Labor management

·       Quality management

·       Process management

·       Maintenance management

·       Product tracking and genealogy

·       Performance analysis

Programmable Logic Control Systems

 

One of the best ways to learn how to properly implement Programmable Logic Controller ( PLC ) systems is by doing. At Factory Automation Systems, we have implemented many successful PLC systems, and with each one our knowledge has grown.

You are the expert on your process. By listening, we implement that expertise into your PLC system. A significant portion of our engineering staff were once successful plant engineers, and all are familiar with the workings of the industrial manufacturing facility. Machine controls of all types

Sample of the processes controller system using  Programmable Logic Controller ( PLC )

·       Web handling lines

·       Paper machines & pulping processes

·       Inventory management & tracking

·       Conveyor systems

·       Bottling lines

·       Paint line scheduling & routing control

·       Textile range line control systems

·       Mixing, batching & blending systems

·       Packaging operations

·       Metals process line control systems

·       Materials and press handling control systems

Integrated Manufacturing Systems

Whether you have a discrete parts operation, a batch or continuous process, information flow, control and management are key elements to your success. Factory Automation Systems will design and integrate a system to provide you with the appropriate level of information--on time and on budget.

·       Production monitoring and reporting

·       Downtime monitoring

·       Date and time stamping of activities

·       Statistical analysis

·       Scheduling routines

·       Routing optimization

·       Recipe management

·       Data acquisition and archival

·       Inventory control systems

·       Database systems

·       Windows to the process

·       DCS replacements

You can use this PLC s and HMI / MMI for the Process Control

PLC

·       Allen-Bradley

·       Siemens

·       GE

·       Modicon

HMI / MMI

·       Rockwell RSView

·       Simantic

·       Siemens WinCC

·       GE Cimplicity

·       Wonderware/ArchestrA

·       PanelView

·       PanelView+

·       Cimplicity ME

·       Modicon

·       QuickPanel

·       Magelis

Machine Vision Systems

Factory Automation Systems has a proven track record of successful machine vision applications in a wide variety of industries using different technologies. Some examples:

·       A robotic machine-handling process which used machine vision to perform orientation, identification and code reading tasks.
Line cameras and diffuse on-axis lighting were used.

·       A robotic palletizing application which used machine vision to identify, locate and pick up objects in dynamic positions while moving on a conveyor.

Motion Control and Drive Systems

Servo and Variable Frequency Drives

When you join forces with Factory Automation Systems, you are assured of a complete drive system solution provided by recognized professionals. Incorporating the optimal choices among power, logic, process and information technologies into one drive system.

·       Common DC bus AC drive systems

·       Multi-motor DC drive systems

·       Servo and positioning systems

Robotics Systems

Robotics Systems

The ability of machines to replace human effort is at an unsurpassed level. Factory Automation Systems offers the experience, creativity and perspective to properly implement robotic system technologies.

We are fully-qualified and experienced in the proper implementation of gantry robot systems, 6-axis articulated arm robots and custom-designed units.

Our experienced staff has successfully completed thousands of robotic system installations. We are industry leaders in creative end-of-arm tooling design and recognized as leaders in robotic system applications. But two qualities separate Factory Automation Systems from other robotic system technology providers:

Creativity

The measure of creativity at Factory Automation Systems is how simple we can make the complex.

Completeness

Factory Automation Systems is expert in multiple technologies: computer integration, discrete controls-PLCs and sensors, drive and motion control systems and robotic systems

FACTORY AUTOMATION TECHNOLOGYS AND BASICS AUTOMATION TECHNIQUE