PLC's Basic Use

Washers, dryers, dishwasher, microwave and electrical oven, alarm systems, automatic light controllers, home automation, swimming pool filters. Every programmable electric appliance can be suitable for PLC controlled. One of my friends manages air pumps, dimmer lights and water heathers of your aquarium using an PLC.

While your post is technically correct I don't believe the question was directed at what devices could be built and controlled with a PLC so washers, dryers, diswasher, etc., don't really fit. The inclusion of "home automation" is answering the question with the question.

The parts of your post I do agree with are swimming pool filter (controls), lighting, alarm systems. I would add irrigation controls (lawn sprinkler), HVAC controls, hot water heater controls with solar assist, swimming pool water level, chemical and temperature control and the like. However, most of the applications would require a significant amount of retrofit and add-on controllable devices. Something like HVAC, to be really effective, would need to have the addition of air duct controls, motion sensors and temperature sensor in individual rooms so that unused areas of the home would be "off loaded" from the system and maintained at minimum levels outside the human comfort zone but to prevent damage from freezing, for an example.

Even light controls would be a pretty significant retrofit of an existing home. To build new would be much easier but now you are moving toward what a commericial/industrial building uses. I myself have considered many of these projects and the only two seem feasible to me, although there would be little or no financial sense, and that is the pool and irrigation controls. It would be fun and techically rewarding but that is about it. That won't keep me from thinking about it and planning it for my dream home someday. Oh, speaking of dream home, a PLC would allow you to switch between or supplement solar and geothermal power, heating, cooling, etc., based on the efficiency, the weather, time of day, activity in the home, and would allow you to monitor and trend it all. Oh, to win the lottery and be able to "play" with stuff like this!

Where would someone pick-up an inexpensive and simple to use PLC for home use, such as for an aquarium? I have a Terrarium with Frogs and several items running at different times/multiple times a day.

Thanks,

Matt

crashmrl@earthlink.net

Hi Matt,

Having an automated system for an aquarium is definitely a very good idea. Keep in mind that once you realize how easy and versatile PLCs are you will more then likely want to use them to do a lot more. I would suggest that it is probably a good idea to select a slightly more expensive and complex system that you initially need because you are almost certainly going to want to expand what it does in the near future.

It depends on your location but a good place to start is our gracious sponsor Global Spec's web site. The link will take you to the registration page and after registering you can use their search engine to find which companies manufacture and supply PLC equipment. It's then a simple matter to select and appropriate model and supplier that is local to you.

Thanks Masu,

I'm now right back where I started, to many choices with a lack of knowing enough to choose one, just want some that is easy to program, just plug everything in and it works? I guess I was hoping that you might be able to recommend a couple of model for about $100.00.

Thanks

World wide there are around 500 companies that supply PLC equipment so it depends greatly on your application as well as your location.

The bigger ones are

• ABB Control, Inc.
• Rockwell
• Panasonic Electric Works
• GE Fanuc Intelligent Platforms
• Siemens Energy & Automation, Inc.

What I suggest doing is finding out which automation companies are local to you and which type of brand of PLC they are selling to give you and idea of what is available.

You will not need a very complex PLC and there are numerous small PLC that can be purchased for around US$100.⁰⁰ that will have more than enough capacity for your needs.

However, the first thing you need to do is make a list of the inputs you will need the PLC to monitor and the outputs you will need to control the equipment. There are two basic types of input that a PLC works with:

• Digital: These are inputs and outputs that are either on or off. For example a switch or sensor is either switched on or switched off or while on the output side you may have something like a light or a pump that is switched on or off by the PLC
• Analogue: These are inputs that are converted to a number by the electronics and can have a range of values. For inputs you may be monitoring things like temperature or pressure using the appropriate sensor while on the output side you may be controlling the speed of a pump or how far a control valve is open.

Once you have an idea of what is available and roughly the inputs and outputs you need its fairly easy to put everything together. If you can send me the information I will help you through selecting, wiring and programming it to do what you want. If you know how to wire a light switch then you shouldn't have much of a problem connecting and programming a PLC

Don't post your email address here but if you follow this link to the CR4 mail system you can send ma a private Message and I will tell you how to contact me directly.

Regards MASU

maybe easier to answer : "In what applications PLC's can not be used for private home applications?"

Please, what is PLC???

Programmable
Logic
Controller

Here is a good link to define what a PLC is:

http://www.plcs.net/

I would like to thank all of you participating on this discussion.

If you are into home automation the a good technique is to use a PLC to interface with the real world and the use a PC that communicates with it to do the really fancy stuff like voice recognition, telephone and network interfacing, data logging etc.