PLCs (Programmable Ladder-logic Controllers) are what industry uses to automate their factories. These versatile controllers are used to automate equipment from rocket fuel plants to bakery ovens.
Ladder-logic is a language that looks (and acts) like an electrical ladder diagram. Ladder-logic is not only a self-documenting-graphical language, but the fastest way to get one-of-a-kind applications up and going. We call Ladder-logic a self-documenting language because when you are finished, you can print out a copy that your plant electrician can read and understand! Why? Because it uses the same graphical representation that electricians call ladder diagrams with the same types of symbols they have been looking at for generations.
As an engineer or hobbyist, you might lash up an electronic contraption to a mechanical contraption to make things move. After staying up all night and writing lines and lines of arcane software incantations, often instead of the intended movements it would just wiggle or vibrate (flutter) or just bang into a mechanical stop (wump). Flutter-wumper work is the heart of all automation.
PLCs make getting past the flutter-wumper stage easy. If we are turning an output on (instead of the off we meant to) we merely change a 'normally-open' to a 'normally-closed'. Back in the old days, we would find address Hex F75D, mask bit 5 if needed, Exclusive OR the result, recompile the code, check for errors, repeat until it sort of worked or double vision from lack of sleep kicked in.
What we have with a PLC is an 'automation controller' (not a computer optimized for general-purpose duties like text editing and rigged up to run a workstation in a production line only to crash and create a pile of scrap). While PCs are great for programming PLCs, they just aren't reliable enough to trust with real world production applications. While it may not be a big deal to get a 'FATAL EXCEPTION ERROR' while writing a letter, it could be a very big deal if you were say, running a high speed web press - or monitoring safety interlocks of a 20,000 ton impact punch. PLCs have simple and robust operating systems. If a PC is being used as a 'User interface' (a user interface is used to display information and to make adjustments and might run under Windows or better yet Linux) and it gets a software hiccup - while you are cursing Mr. Gates during reboot, the PLC keeps everything working safely and smoothly.
What makes the use of PLCs a revolution today is that the price has gone down to the point (how about $200!) that it is often much cheaper than what industrial OEMs have been offering as their custom extra feature package for their latest machine! This means not only can you upgrade your equipment to do the new things the OEM is offering, but you can have it do even more and while you are at it, have it do it your way!
PLCs can talk to your PC through a 'software protocol' or to each other; sharing data or receiving data that tells it what to do! Networking is natural to them -- PLCs have been talking to each other before you had a network card!
Programming PLCs can be a profitable career. Hourly rates go from $65 to $175 for an experienced programmer. If you want to save or make money, learn to program yourself - it's easy. The Toshiba line of PLCs has the best programming interface on the market. It runs under Windows 95, NT, XP and our programmers claim they can do twice the work in the time it takes with 'other' brands. That means money in your pocket! Your program work can be password protected so you can sell it as part of a product!
A 'brick' PLC has a block shaped case (hence a 'brick') with terminal strips on it. They can be panel or DIN rail mounted but come in a model-number-determined set of I/O capabilities.
A 'Rack' has one or more 'card racks' that individual circuit cards slide into so you can pick and choose your I/O to whatever number and/or type you need. (There is the exception with some of the T1 series of bricks - some also have a way to add a few extra cards and yet another connection so you can add a real rack!)
These PLCs have an RS232 connection and protocol that allows you to read and write any of the registers (for more information see the Computer Link page ). . There are third party software packages that provide GUI interfaces as well as LCD touch screens. The protocol is a simple ASCII format. You can access and set the information with any program language. Using the simple RS232 can be accomplished using the programming cable that comes with the starter kit. There are also high speed networking capabilities available. Also the Toshiba has a simple ASCII protocol that gives you access to all the registers. Several third party user interface packages support it - or just write your own to run on a PC - it's simpler than you think. For more information download the computer link manual. And the modem control manual Also, see a Linux example using the computer link function. Or ask Transtronics about writing a custom GUI (Graphics User Interface) for your application.
Transtronics not only offers PLCs but we offer 'glue devices' that gets your application out the door. Some of our solutions: Need to run your equipment off an auto or truck electric system? See our DC-DC converter. Need to interface to some Logic level signals see our CMOS and TTL couplers. We also have a line of panel meters that sometimes do little jobs needing a display just as well as a PLC. See our 12V battery backup solution.
Available cards include input cards (Analog, discrete [24Vdc, 120Vac] and logic level), output cards (Triac, Relay, open collector and analog), special purpose cards such as pulse counters or stepper motor controllers. Most models can be networked together to share information from remote parts of the factory floor. Very inexpensive controllers with limited I/O are part of the line.
First, the software programming package is the same for bricks, Racks and advanced T series PLC. If a brick project gets larger the program can be easily transfered to a rack or advanced system. This also means that you only need to learn one software package.
MoreAutomation needs to be reliable - no plant wants down time - and if you have installed a PLC 3 states away - an equipment failure means putting someone on a plane, setting them up at a hotel -- something that could cost $1000. That is where Toshiba PLCs come in. Once they are up and running - they stay up and running.
Toshiba is known worldwide for their extremely high MTBF of their PLCs besides the excellent programming software. Toshiba uses these PLCs in their semiconductor and consumer electronic plants, which I believe, caused the creation of a far above average software environment and extremely high quality product. Our own in house programmers have consistently requested Toshiba PLCs when given the choice (they have worked with all the major brands). That is the sole reason we sell Toshiba PLCs.
Toshiba PLCs were originally designed for internal use in Toshiba factories. The engineers who design the equipment had to use it. Interestingly when the engineers have to use their own equipment, good things happen. Combined with excellent design and reliability, is the great software. (For more about the programming software down load the quick start manual). The windows based software makes programming just a matter of dragging and dropping the symbols into place. If you want the best in a laptop you ask for a Toshiba - if you want the best in a PLC ask for Toshiba.
You probably do not want to use 120Vac logic unless forced to. We recommend using DC input cards and relay outputs for most applications. This increases safety, and reliability and reduces system cost We also have ac to PLC dc-input logic level converter modules for applications that require monitoring a few 120Vac inputs.
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