Comparison Instructions

IN1 and IN2 are compared according to the type of comparison you choose:

==     IN1  is equal to  IN2

                                                                              <>     IN1  is not equal to  IN2

 

 >       IN1  is greater than  IN2

<       IN1  is less than  IN2

>=     IN1  is greater than  or equal to  IN2

<=     IN1  is less than  or  equal to  IN2

NEW PLC tutorial and guides for automation

hi there, this blog is dedicated to provide you with PLC tutorial specifically for industrial automation and robotics.



There are two types of PLC available in the market, which is relay type and transistor type. the major difference between these two is the response time. The response for transistor type PLC can go as fast as 0.5 microsecs compared to those of relay types which have response time around 10 ~ 20 millisecs.

The ability of transistor type PLC to do fast switiching makes it possible for it to have pulse outputs and high speed input to control AC servo motor.

Planning your project plc

It is very important to plan your work in designing your PLC projects. identify your project requirements, inputs and outputs involve etc.



Today i will give you a free PLC programming on how to do a PLC controller for a water tank system. This is a typical exam question for PLC beginner.

The inputs involve are 1 start button addressed at 0.00 and 2 level switches addressed at 0.01 and 0.02 respectively. The one address at 0.01 will turn ON whenever the tank is empty thus it will switch ON the water valve (output) which is address at 10.00. The other level switch will turn ON whenever the tank is full and consequently will turn the water valve OFF. By doing this control, the water tank will not run empty. The water will fill into the tank whenever the empty switch is ON. Address 14.00 and 14.01 is just internal relay address to sequence the programming.

two stage counter Free PLC

When an SV higher than 9999 is required, two counters can be combined as shown in the following example. In this case, two CNT instructions are combined to make a BCD counter with an SV of 20,000.

long term timers

Example 1:
Long-term Timers
The following program examples show two ways to create long-term timers
with standard TIM and CNT instructions.
Two TIM Instructions
In this example, two TIM instructions are combined to make a 30-minute
timer.




TIM and CNT Instructions

In this example, a TIM instruction and a CNT instruction are combined to make a 500-second timer.TIM 0001 generates a pulse every 5 s and CNT 0002 counts these pulses. The set value for this combination is the timer interval × counter SV. In this case, the timer SV would be 5 s x 100 = 500 s. With this combination, thelong-term timer’s PV is actually the PV of a counter, which is maintained through power interruptions.

PLC tutorial open source, free codes for you 2015

This is your source for PLC programming. Finally, a FREE place to practice your PLC programming skills. The PLC Simulator is here to help you learn PLC programming.
For simple directions please view the help section. The help section can be found on the top menu of the PLC simulator.

Suggestions for improvement are always welcomed. If you would like to share any of the PLC programs you write via the simulator, please upload them to the downloads section of the site. You may also wish to search there for some examples other people have written.

Enjoy the program and remember that your feedback is welcomed as well as your suggestions for improvement. NO requested feature will be considered crazy.

PLC MINI-TUTORIAL

This document is designed to give an overview of what a PLC is, what it is good for, what it is not best at, an overview of its operation and where to find more information. A Programmable Logic Controller (PLC) is a rugged special purpose computer that reads a bunch of input signals; runs control logic, and then writes output signals. After reviewing this mini-tutorial please feel free to ask us questions or ask about a free seminar and demonstration at your site.

Pros

1. PLCs are good at turning outputs on or off based on the state of inputs. (control)
2. PLCs are good at bringing together and concentrating a lot of data and status that is uploaded into a computer in a compact form
3. PLCs are more rugged than computers and typically last five, seven, ten years without needing replacement

Cons

1. PLCs are not the best at handling large amounts of data or complex data.
2. PLCs are not the best at reading and writing databases.
3. PLCs are not the best at outputting resultant data to printers.
4. PLCs are not the best at displaying data and information to the operator.

History

Programmable Logic Controllers (PLCs) have been around since the dinosaurs. In fact it was PLCs that killed the dinosaurs. Don’t listen to those people that tell you that dinosaurs were killed off by global warming / cooling, meteors, or even smoking cigarettes. PLCs killed the dinosaurs. You see, millions of years ago the cavemen used PLCs for everything they did. All of the dinosaurs lost their jobs, couldn’t afford to buy food at the local stoney-mart and just died off.

Okay, okay I guess I have to admit that the last paragraph is not true. But the PLC has been around since at least the 1960s, which in technology years makes it a dinosaur. For the real history of the PLC follow this link  to the website of Dick Morley, the inventor of the PLC (just don’t forget where to come back to).