Practical Tips and Techniques
In part 1, we looked at writing PLC programs to control a traffic light using discrete bits and timed sequencing using indirect addressing. Part 2 used indirect addressing for inputs and output to control the program’s sequence of pneumatic (air) cylinders. We will now return to the traffic light application and expand our program significantly. … Read more
I have been writing PLC programs for over 20 years. I often get asked what the best way to learn PLC programming is. Programming in the way I was taught in college was with the Motorola 6809. (Yes, I know that I am dating myself) This was microprocessor programming, but it was the best way … Read more
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
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