Tag: ladder logic

Ladder Logic 104: Memory Organization

One of the first decisions that needs to be made when designing a PLC system is memory allocation and organization. In the early years of the PLC memory came at a premium… 1K (one kilobyte) of memory for the program

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Ladder Logic 304: Timer Application

Today’s post is in response to Dave Tompkins, who posted a request for help last week for an application. Since he posted it on one of my series posts on ladder logic (204: Auto Sequences) I decided to frame it

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Ladder Logic 303: PLC Forensics

Today’s topic involves a project I have been working on over the last few months. The project consists of adding process equipment including tanks, pumps, valves and instrumentation to an existing system… while it is running. Because production runs 24

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Siemens PLCs

Continuing the series I began last week with the Allen-Bradley PLC platform, this week I am discussing the Siemens family. My first exposure to Siemens PLCs was in the late 1990s when I customer wanted a quote on upgrading their

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Ladder Logic 207: Interrupts and Periodic Tasks

Today’s post is in response to Darko’s comment on my Ladder Logic 206: Scanning post. He mentioned that readers might want to learn a little bit about interrupts. It can be difficult to discuss this subject generically since different manufacturers

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Ladder Logic 103: More on Program Organization

Today’s post covers a bit more on program organization and layout. A reader posted a question on a previous post “Ladder Logic 204: Auto Sequences”: “Iā€™m still really new to the field and have yet to create my own program

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Excel – Automate your Automation

Probably the most useful tool I have in my arsenal when doing preliminary design is Microsoft Excel. In many of the projects I have worked on over the last couple of years since I left Wright, the company I was

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Ladder Logic 302: Data Tracking and Structure Data Type

Today’s post is the second “advanced” topic I have covered on PLC ladder logic, The first being toggle circuits. It is often necessary to track data on individual parts through a machine or production line. If using devices like barcode/datamatrix

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Ladder Logic 301: Toggle

Today’s post is the first “advanced” topic I have covered in this blog. By advanced, I mean that rather than covering basic information on Ladder Logic and program structure like I did in my 100 Series, or general programming routines

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Ladder Logic 206: Scanning

In last week’s post I mentioned that there was a mistake in the organization chart I have been using in my ladder logic posts. My friend Gordon mentioned it at lunch a couple of weeks ago and when I checked

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