PLC Basics

Now You Can Have Robust Data Logging for Free – Part 1

by

Robust PLC Data Logger   With traditional loggers, the software will read the memory of the PLC and store it in a local computer. If the network stops or PLC communication fails, the logging will stop. Creating a robust PLC data logger allows communication to be stopped without losing any of the data for collection. … Read more

… and I also do PLC programming.

by

Programmable Logic Controller (PLC) programming is often thought of as something everyone can do easily. We often design the system, install the hardware and then start to think about the PLC program and programmers. This approach can be improved. The landscape of PLC programming is changing, and we must also change. Computer Programming / PLC … Read more

Changing Landscape of PLC Programming

by

With today’s new processing and networking power, the future looks bright for programmable logic controllers and their programming. This has allowed the role of the PLC to expand. System Design: PLC design has changed significantly. Computer processing power has now added the following to programmable controllers: Micro USB slots (Data Storage) Ethernet ports WiFi RS232 … Read more

Creating More Than Just A PLC Program

by

A collection of random thoughts on PLC programming and doing more than just basic logic and making your program intuitive. PLC programs usually control the logic between the inputs and outputs. If this turns on and that is not on, then this output is on, blah blah blah. Programmable logic controller programs can go far … Read more

Here is a Method That can Help You with Difficult Level Sensing

by

Turn a capacitive proximity sensor into a level sensor. This is ideal for tanks and vessels you cannot drill through the side for mounting. Wrap the bare wire around the sensing head and extend it to the length you need to detect. Insulate the wire using electrical tape, but leave the end exposed. This acts … Read more

Get Rid Of Surges That Are Destroying Your PLC Outputs

by

DC Solenoids are the worse culprits for electrical surges in your system. When the electrically generated field collapses, an opposite polarity voltage is generated. This voltage spike can be high enough to weld the contacts on a PLC output relay. To protect your PLC output relay, use a diode to ensure that the voltage spike … Read more

Building a PLC Program That You Can Be Proud Of – Part 2

by

In part 1, we looked at writing PLC programs to control a traffic light using discrete bits and timed sequencing using indirect addressing. We will now look at how we can use indirect addressing for inputs and output to control the sequence in the program. Let’s look at an example of controlling pneumatic (air) cylinders. … Read more

Building a PLC Program That You Can Be Proud Of – Part 1

by

What is the best way to program a PLC?  My answer is simple. The best way is one in which someone can look at your program and understand it. I cannot stress the need for good documentation of your program enough. The best programs are ones that I can return to after several years and … Read more

Who Else Wants To Know How A PLC Scans?

by

Programmable Logic Controllers (PLC) will scan very quickly. This can be anywhere from 1 to 20 ms, translating into 1000 to 500 times each second. But what exactly is a scan? A scan is when the PLC will complete the following: Read Inputs: Look at all of the inputs to the programmable controller. Digital, Analog, … Read more

Here’s a Quick Way to Connect RS232 Equipment

by

Most programmable controllers will come with an RS232 communication port. This recommended standard (RS) has voltage signals between 3 to 15 volts DC concerning the ground/common pin. RS232 devices are called DTE (data terminal equipment) or DCE (data communication equipment). The maximum cable length for the communication cable is 15m; however, depending on the environment, … Read more