Control of home appliances through mobile phone.

Could this be another example of electronic gadgets doing away from the need to think?

Amongst others, Carlo Gavazzi has a system that connects a network of sensors and switches through a cellphone. works fantastic !

http://www.carlogavazzi.com/Gavazzi/page43.do

go to "dupline"

It is very easy to set this up.

You need a PLC with serial connection port (RS232) and an SMS modem.

The PLC can send you text messages on detected events.

You can send messages to the PLC, he will translate them and do the correct action.

If you can do some basic programming you can do this yourself.

Wago has some examples on how to couple SMS modems to their PLCs, but in fact all the PLC suppliers should be able to tell you what will work together from their range.

is a sollution too ... of course ... but I guess that PLC's and serial connections, programming etc ... might be over the top for house appliances, no ?

The system I was referring to is some kinda bussystem, and does not need any serial connections, programming PLC's etc... the "programming" of this (these) bussystems is so easy... really !...

You will have to do something to couple the info from the house bussytem to the GSM.

I know that the bussystems are easy to program, but I assumed that the originator wants to build something and start to sell it, not go to the shop and buy a ready system.

The PLC approach is the nicest, you are so free to do what you want, just add the function and ready. The bussystems are limited and adding functions is so expensive.

Dear Sir,

Thank you for your response. In fact I did a project with a PLC and I don't think the programming would be a big problem. My concern is as to how to interface the MAINS to the input and output of the PLC.

Grateful if you could kindly advise.

Thanks & Best Regards,

SJ

If you go for a PLC you will find outputs that can drive 240V AC. typical 2A.

Simple lights can be direct connected. Larger loads can be swtiched through relay's.

Inputs in general are a bit different, they normally require a low voltage, what you can do is work with small 240V relays with a switching pole contact, the common is connected to the input, one pole to the 0 level, the other to the 1 level.

When you design your own microcontroller you can work with opto coupled triac drivers (eg K3021P), these circuits do a galvanic separation between your logic (5V DC) and the power side (240V AC) in a single housing and very few components.

There also exist very nice dimmers, that can handle a current (4-20mA) or voltage (0-10V) input and transform it into a nice cut sinus. Work with decent separation, filters and shielded cables to prevent humming. (Carlo Gavazzi does has nice stuff)

The input can be done again with relays or opto couplers.

Why would you have 240V inputs? Pushbuttons can deliver the low level input, and in home applications the cable lengths do not pose problems.

Hi surjunlal,

I did a project with a PLC and I don't think the programming would be a big problem. My concern is as to how to interface the MAINS to the input and output of the PLC.

I have the feeling that you have a different interpretation of the term PLC (Programmable Logic Controller) that the rest of us.

A PLC is normally specifically designed for interfacing directly with mains voltages without any additional equipment. The concept of a PLC is a system that can easily be use to control the real world equipment at mains voltages as simply and easily as possible.

There a host of companies that manufacture PLCs and here are some links to the relevant pages of some of the larger manufacturers, ABB, Rockwell, Panasonic but there are many more on the GlobalSpecs web site that you may be more familiar with.

There are many variations on the concept of a PLC but the core of the system usually consists of a CPU (Central Processing Unit) to which you add IO (Input Output) modules which are selected according to the type of inputs you wish to sense and outputs you are trying to control. Most of them will at a bare minimum have IO modules that are capable of both sensing and switching mains voltages of 110-240 VAC at currents of up to !0 A.

Are these the sort of thing that you in you project or are you referring to a MCU (Microcontroller) which is a single chip that contains a CPU, Memory and IO circuitry that can be programmed to perform a specific task?

Dear Sir,

Thanks for your input.

I am referring to PLC, Programmable Logic Controller itself. In fact I was trying to know how can I use the outputs of the PLC to switch on the appliances as the ampere requirements for some appliances are different from others. I would also like to know how can I protect the PLC or appliances from any surge currents or overvoltages.

I know that microcontrollers can also do the job, and I guess there would be much to do for interfacing (using other modules) with the microcontrollers.

Thanks & Kind Regards,

SJ

If you are using a PLC that has an IO card that is capable of switching mains voltages the only thing you need to worry about is that you don't draw too much load for that particular device.

It depends on the brand and options you select but you will find that most manufacturers will have an output card that can switch 240 VAC and cope with a 10 A load. There are several ways that they actually do this but the methodology is irrelevant and all you need to do is keep within the design limitations for the output.

If you have devices that craw currents that are higher than the PLC outputs can drive then all you need to do is install a contactor or relay as an intermediate stage and drive that with the output of the PLC.

The whole concept of a PLC is that for all intense and purposes the outputs act as relays and you wire them the same way you would wire a relay. Provided the current draw and voltages are within the design limits of the PLC output it can be connected directly to the load and you don't need to consider anything else.

If you would like I can have a look at your load specifications and work out the sort of output that your PLC would require.

There has been a few systems for cottage owners since the 70's/80's that are of a similar application to what you need. I know of one guy that "phones" his remote cottage and sets the building heat to the desired temperature before he leaves work to head to the cottage for the weekend. The system also has a "freeze" alarm that phones him if the ambient in the building drops to near freezing.

Being of an old technology I'm sure you could find a used system that you could adapt.

Search the web for cottage links, or maybe Homepower Magazine, or the like.

just a thought

I built a home automation system about 13 years ago that was based on a PC. Initially it could annunciate problems like intruders using a pager but a later update added the capability of calling a mobile phone and verbally annunciating events.

Having said that I am currently thinking about building a new more sophisticated system and have come to the conclusion that the way to go is use a PLC to interface with the real world and switch things on and off that is interfaced with a PC that handles the more complex tasks like voice generation and recognition.

The limitation of a system like this is your imagination and the use of a mobile phone as a remote control console is a logical extension. There are a multitude of ways to achieve this but I would suspect that the using the SMS system to send messages back and forwards that can be interpreted by the receiving system as control commands.

Sounds like a fun project so please don't forget us at CR4 and give us a post with the end results.

Dear Sir/Madam,

Thank you for your reply. I am familiar with PLC as I did a project with PLC RSLogix500 and I don't think it would be a big problem with the programming.

My actual concern is the interface between the PLC, mains power, and the mobile phone. Thought with a PLC it would cost more compared to a microcontroller!

Grateful if you could assist.

Thanks & Best Regards

SJ

My actual concern is the interface between the PLC, mains power, and the mobile phone. Thought with a PLC it would cost more compared to a microcontroller!

If you wish to use a microcontroller you will more than likely end up paying more as building circuitry that can switch mains voltages is fairly difficult. If you do it wrong you can cause a lot of damage to both the equipment and yourself. There are also a hell of a lot of traps and if you havn't had a fair amount of experience with switching mains voltages electronically I would suggest using the PLC. Remember a PLC is really a microcontroller specifically configured for switching mains voltages.

For the phone interface part yes this is going to be difficult with a PLC. However if you do use a PLC you need a PC to program it in the first place so you can use the PC for doing the fancy stuff with the man machine interface. You use the PC to do the complicated stuff and then just pass commands to the PLC via some sort of interface. The system I build talks and there is no reason that you cant use voice recognition to generate commands that the PLC executes.

By using a combination of a PLC and PC the only limit is your imagination. A system like this would have more computing capacity than the space shuttle and look what that can do.

Dear Sir,

I think I'll go for PLC for the interface between the appliances and mains. However, I'll be grateful if you could help me concerning an interface for the inputs, i.e, the signal from the mobile phone to the PLC.

Thanks for your help and support.

Best Regards,

SJ

Hi Surjunlal,

I think you have made a wise decision. Have you ever played with voice recognition software? If you have a simple way would be t get hold of a modem that has a inbuilt telephone function and connect the modem inputs and outputs to the sound card in a PC.

You then need to write a program that will answer the modem when it sees it ring and listen for the tones of the buttons you press. If you get really fancy you could go all the way and get it to interpret verbal commands.

Another method is to get a PLC that has an internet interface on it and connect it to the net. You can then use the SMS (Short Message System) on the mobile to send commands to the PLC. If you can't get a PLC that is internet capable then use a PC to do the internet interface and do the same sort of thing.

The only limit is your imagination.

Dear Sir,

Thanks for your assistance. Unfortunately, I've not used a voice recognition software.

I'll try to see a PLC which can be used with internet or modem.

Best Regards,

SJ

i want to know more about this project....

plz mail me..

Plz mail me.

Nice, log in first and tell us who you are.

Second star from right?

Gwen

Surju, I was looking for something else but I stumbled across something that I thought would interest you. It's a GSM Alarm Transmitter & Receiver That has two relays that that can be controlled from a mobile phone and it can be upgraded to control 8 relays. That doesn't sound much but if you use it as an interface and each output as a bit you have 256 different combinations that you could use.

Unfortunately it's pretty expensive but at least you know that there are devices out there that can do what you are trying to.

We are working on a little device that controls the temperature of a room, has an alarm input and a control output, connected to a GSM module.

As soon as it is available I will send a link.

Gwen

Thanks & Best Regards,

SJ

Dear Sir,

Thank you very much. I'll verify and let you know.

Best Regards,

SJ

Dear Sir,

Hope you are fine. Sorry for the late reply. In fact my requirements range from 3Amps to 13 Amps. However, I shall check for the requirenments for an Air Conditioning Unit.

Thanks for your support.

Best Regards,

S. JHURRY