How to Troubleshoot a PLC – Ladder Logic

We will look at how to troubleshoot a plc racing condition. Two examples are explained in racing conditions in the PLC. The PLC will update only at the end of the program logic. Items set will not happen until the I/O is refreshed. How to trigger events when you want them is discussed. Your control … Read more

Here is a Method for a Faster PLC Program

PLC programming involves both direct and indirect addressing. Direct address programming involves writing each ladder logic rung to do the operation required. We often forget about using powerful indirect addressing to solve our logic. Indirect Addressing – Faster PLC Program The below-animated picture will show a simple example of using indirect addressing. This will use … Read more

The Secret of Using Timers – PLC Programming

We will now look at the secret of using timers in the PLC. Timers are used in the majority of PLC programs. There are also a wide variety of off-the-shelf industrial timers that you can use. The implementation of timers can be vast; however, it all starts with a TIMING CHART. Timing Chart – Secret … Read more

Here’s a Quick Way to Wire NPN and PNP devices

Here’s a Quick Way to Wire NPN and PNP devices I often get asked how to wire NPN and PNP devices to the programmable logic controller. This can be unclear at first when looking at the wiring diagrams. I have managed to destroy a few sensors in the process….. so let’s get started, and I … Read more

How to make a Start Stop Jog circuit in a PLC

Looking at a stop-start jog circuit in the PLC will help us understand the differences in hard-wiring the circuit and programming. Basic Start Stop Circuit Let’s start with the primary start-stop circuit. Here is what it looks like hard-wired. (Physical switches wired to outputs devices, such as motor contactors and relays.) When the start pushbutton … Read more

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

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