Programmable Logic Controllers (PLCs) are forever upgrading and changing to stay current with today’s technologies. Everyday we hear of new and improved cell phones, handheld computers, GPS systems, etc. The same holds true for PLCs. Every year new models of PLCs are introduced into the marketplace. This article is going to touch on some of the new features available on PLCs.

Programmable Logic Controller - Features

Eugene Kowch

Programmable Logic Controller - Features

Author: Eugene Kowch, P.I.D. Consultants Inc.

 

Programmable Logic Controllers (PLCs) are forever upgrading and changing to stay current with today’s technologies. Everyday we hear of new and improved cell phones, handheld computers, GPS systems, etc. The same holds true for PLCs. Every year new models of PLCs are introduced into the marketplace. This article is going to touch on some of the new features available on PLCs.

 

One of the obvious new features is how compact in size PLCs are becoming. PLCs are now about the size of a hockey puck, 4” H, 4” W and 2.5” D. These compact PLCs come with a built in LCD display and keypad or a colour touch screen (160x128 pixels). These models also come with built-in hardwired inputs and outputs (I/O) electrically connecting to various switches and lights throughout a building. Now that is a lot of PLC in a small package.

1Data storage memory is important to a PLC. To have a removable mass storage device would be a great feature for a PLC. MicroSD is a dime-sized memory device found in today’s cameras and cell phones and now is available to PLCs. Memory densities ranging from 128MB to 2 GB. This is ideal for application files and users can easily update their PLC ladder program through this memory device.

Communications with other electrical systems is important for PLCs. PLCs used to have only one RS232 serial port, but now there are at least two RS232 serial ports on every PLC. This allows for cross control between two different electrical systems like lighting and drapery motors or audio/video equipment. PLCs have their own networking systems so that you can connect other PLCs and I/O modules together. Imagine having a dedicated PLC for heating/ventilation and a dedicated PLC for pool/spa control networked with a PLC doing lighting control all sharing data to a central PLC with a touch screen display showing all the above systems.

Programming the PLC is via a desktop or laptop computer using proprietary free software. This software never use to be free, but nowadays to keep up with forever changing features, the PLC programmer just has to check the Internet for recent revisions and upload the new software. Also, the programming port has changed to a USB type instead of using one of the RS232 ports mentioned above. This frees up the RS232 port for control and allows the programmer to view his program on line for trouble shooting purposes.

Mentioning the Internet above, wouldn’t it be nice if a PLC could connect to the Internet. Well now it can. Some models come with a built-in Ethernet connection, but most have an optional card with 10/100Mbit. Now add a HTTP server and the PLC can now receive and display information on ones own web home page. Could you imagine checking up on your home from a vacation resort somewhere in the Caribbean.


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There are other communication options available to the PLC. How about a GSM/GPRS cellular, telephone modem or a 900MHz radio modem. All these are optional cards that are easily installable. Imagine getting a phone call from your PLC informing you of a problem at home, like a security alarm, when you are away.

These features are available to PLCs today. What new features will we see next year?


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