Programmable Logic Controller

Master PLC One-Shot Programming: Stop Runaway Code Forever!

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A one-shot in the PLC will turn an output on for one scan. This is used to trigger events that should only happen once. An example of this would be to increment a value in memory. If a one-shot is not used, then every scan of the PLC will increment the value. What is a … Read more

Master PLC Flip-Flops: Toggle Outputs with One Input!

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A flip-flop circuit in a PLC usually has one input and two outputs. When the input is activated, the two outputs alternately latch on/off opposite each other. It is used to toggle (latch) work on and off with just one input. In the PLC, it is a single input that will toggle an output on … Read more

Building a PLC Program Part 3 – Traffic Light

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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

Free PLC Programming Secrets: Learn Without Hardware!

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plc basics programmable logic controller

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

Unlock 32-Device Control: Omron’s Secret Protocol Revealed

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The hostlink communication protocol is a method developed by Omron for communication to PLCs and other equipment. This ASCII-based protocol is used over RS232 or RS422/RS485. It is a many-to-one implementation, meaning you can communicate with up to 32 devices back to a master. (1: N) This communication on the industrial floor can control PLCs, Temperature … Read more

How to make a Start Stop Jog circuit in a PLC

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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

Now You Can Have Robust Data Logging for Free – Part 12

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Now You Can Have Robust Data Logging for Free – Part 12 HTML and Scripting Languages  We have the following accomplished: PLC program Visual Basic Program Data collected in a Database IIS web service established ASP Script Written Let’s take a closer look at the ASP Script ( AccRL.asp) that was written in part 11: … Read more

Now You Can Have Robust Data Logging for Free – Part 11

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Now You Can Have Robust Data Logging for Free – Part 11 HTML and Scripting Languages  We have the following accomplished: PLC program Visual Basic Program Data collected in a Database IIS web service established The IIS web service machine must have the Microsoft Access Database Engine 2010 installed. The following link can obtain this: … Read more

Now You Can Have Robust Data Logging for Free – Part 10

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Now You Can Have Robust Data Logging for Free – Part 10 Computer Web Server (IIS)  We have come a long way. The PLC program has been written. The primary visual program has been reported. Information is now being collected from the Do-more PLC via Modbus TCP and stored in a database using visual basic. … Read more

Now You Can Have Robust Data Logging for Free – Part 9

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Now You Can Have Robust Data Logging for Free – Part 9 Computer Program Visual Basic (VB6) Continue   The final code will be completed for the program. If you want a link to download the complete code, go to the contact page and put a Robust Logger Program in the description. The actual code … Read more