AX Control, Inc.

What is a Programmable Logic Controller?

A useful Infographic covering some of the most-asked questions about PLCs.

FAQs, and an Infographic you can use.

How does a programmable logic controller work?

A PLC works like a computer. The CPU manipulates and processes input signals and executes instructions to control output devices. These are the controllers behind most modern industrial automation.

What are programmable logic controllers used for?

PLCs are used in industrial settings for the control of light fixtures, machinery, and assembly lines. They are also used to control other things such as amusement park rides.

Programmable Logic Controller Infographic — Download a high-quality PDF of this infographic below.

Programmable-Logic-Controller-Basics Download

Are there different types of PLCs?

Yes. There are Relay Output PLCs, Transistor Output PLCs, and Triac Output PLCs. The name of each type of PLC derives from its output. Relay outputs are solid-state outputs or mechanical contacts. Transistor outputs are solid-state switches, but can only handle DC current. Low-power AC loads use Triac outputs. This includes motor starters and lighting.

Mechanical design is another way to categorize PLCs. For example, a “brick” is one type of PLC design. This is a small PLC that includes the CPU, the power supply, and the inputs/outputs in one small case. One type of brick PLC is the DirectLogic 05.

An example of a Brick PLC. — A Direct Logic D0-05DA is a type of Brick PLC.

Other PLCs are modular. Modular PLCs have a rack system that has space for different modules. These modules can provide different functions and may act as the PLC’s power supply, I/O, communication interface, or processor.

An example of a modular PLC — The Automation Direct DirectLogic 405 is an example of a modular PLC.

How are PLCs programmed?

PLCs use a traditional programming language that mimics circuit diagrams; this is called ladder logic. Other PLCs may use programming languages like Function Block Diagram (FBD), Instruction List (IL), Sequential Function Chart (SFC), or Structured Text (ST). IEC 61131–3 standard defines these languages.

What are the advantages of using a PLC?

There are several. PLCs are easy to install, maintain, and troubleshoot. They are flexible by nature and offer many different operations. Also, they offer a rugged design specifically for industrial processes. Finally, they’re cost-effective.

Are There Disadvantages to PLCs?

The most common disadvantage to PLCs stems from interoperability or lack thereof.

Originally, manufacturers created PLCs using their own proprietary software and programming. When machines did their own thing, separated from the rest of the machinery on the factory floor, that was fine.

But now we have IIoT efficiencies to think about. Machines need to “talk” to each other and share information. Unfortunately, older PLC design doesn’t allow this.

Luckily, industry groups are now working to solve this problem through new forms of open-access middleware like MQTT, AMQP, and CoAP.

If you need a PLC for your industrial processes, talk to the staff at AX Control today. We’re here to help! We offer many brands of PLC systems and replacement parts, including the popular GE Fanuc PLCs.

Peer-to-Peer Solar MicroGrids Democratize Power

Picture of solar microgrids in use in Germany. — Solar microgrids in use in Freiburg, Germany. Photo by Andrewglaser at English Wikipedia, CC BY-SA 3.0

How solar microgrids work

Imagine an energy trading economy like the consumer food economy where the end-user can buy products from wherever they want. They can use an energy purchase model like most people today, buying from whatever large provider serves their city or state. They will pay a known, stable price.

But if they want, they can participate in a homegrown, local economy. In this model, energy can come from a small business located in the next town or from a co-op around the block. It might even originate from their neighbor. The price may go up and down according to an agreement made for one day, one week, or for a month.

Consumers even have the option of creating their own power. If they have extra, they can distribute it at a reduced rate, or even give it away to family and friends. Imagine giving away energy like you would homegrown vegetables.

Peer-to-peer smart grids using blockchain can achieve this model. In some places, it already has. Exergy is a microgrid platform located in Brooklyn, supporting peer-to-peer energy contracts between users through blockchain transactions. This type of peer-to-peer economy with blockchain transactions has several advantages over previous solar models where users sold excess power back to a primary provider.

The advantages of solar microgrids

Cognex InSight: Answers to FAQs

What Is Cognex InSight?

Cognex InSight is a family of vision systems typically used on the factory floor to identify, inspect, and guide parts. Depending on the model, In-Sight cameras offer high-resolution and high-speed built into a rugged body capable of holding up to demanding industrial applications with pinpoint accuracy.

How to Find the IP Address of a Cognex InSight Vision System

New Cognex vision systems have DHCP (Dynamic Host Configuration Protocol) enabled. This means your camera will listen for a DHCP server to assign it an address. However, if this does not happen automatically the Cognex In-Sight camera will default to a Link-Local IP address in the 169.254.xxx.xxx range.