Device control using Telephone
Wednesday, November 5th, 2008Controlling devices using switches are common. From a few decades controlling devices using remote control switches like infrared remote control switch, wireless remote control switches, light activated switches re becoming popular. But these technologies have their own limitations. Laser beams are harmful to mankind. Some technologies like IR remote control are used for short distance applications. In such case if we have system which does not require any radiations or which is not harmful, long remote control switch!! Yes here is the solution. Here I am introducing such a system which does not require any radiations, any laser beam which has no limitation of range, I mean it can be used from any distance from meters to thousand kilometers using a simple telephone line or mobile phone.
Here I am using a telephone as a media, which serves main part of this system. By using home phone as a local phone and another phone – either landline or mobile phone as a remote phone we are controlling devices.
Features:-
- You can control up to 10 devices. It may be any electric or electronic appliances or devices with simple to heavy appliances. Each device is given a unique code.
- It makes accurate switching, any false switching of device are not done.
- There is no risk for false switching.
- Your local phone (i.e., home phone or office phone) can be used for normal use by using a DPDT switch. So you need not use a separate telephone line for this device controlling.
- To perform any operations through remote phone line, the user needs to dial to the local telephone (to which the interfacing circuit is connected) then the respective code of the device is dialed.
- This circuit does not require any complex IC, so any one with little knowledge of electronics can construct this circuit, because it does not need any programmable IC’s or programming.
- This system detects the ringing signal from your exchange with the help of ring detector and automatically switches ON.
- This device saves your money. This circuit switches OFF after a time of 60 seconds (you can change this switch ON-Time which is discussed in detail in coming section).
- Before changing the state of the device we can confirm the present status of the device.
- This circuit gives an acknowledgement tone after switching ON the devices to confirm the status of the device.
- You can control devices from local telephone. It can also be controlled by PCO.
Taking a tour of the project:
This system uses Dual Tone Multi Frequency (DTMF) technology of our telephone set. Every telephone set will have this facility. We have two type of dialing facilities in our telephone system (i) Pulse dialing mode (ii) Tone dialing mode. Here this system works on tone dialing mode. The DTMF mode is shortly called as tone dialing mode. (Check for availability of tone dialing mode in your telephone set).
This system is divided into two sections
1: Remote Section:
It is nothing but remote telephone set which is present in the remote place. This may be your workspace (office / school) phone or mobile phone or a phone in PCO. Signals are sent through this telephone.
2: Local Control Section:
This is a control system through which you can control your appliances. This contains one telephone line and a control unit. The appliances to be controlled must be connected to telephone line through control unit .Control unit is kept with a sufficient backup.
What is DTMF?
When you press a button in the telephone set keypad, a connection is made that generates a resultant signal of two tones at the same time. These two tones are taken from a row frequency and a column frequency. The resultant frequency signal is called “Dual Tone Multiple Frequency”. These tones are identical and unique.
A DTMF signal is the algebraic sum of two different audio frequencies, and can be expressed as follows:
f(t) = A0sin(2*П*fa*t) + B0sin(2*П*fb*t) + ……….. ——->(1)
Where fa and fb are two different audio frequencies with A and B as their peak amplitudes and f as the resultant DTMF signal. fa belongs to the low frequency group and fb belongs to the high frequency group.
Each of the low and high frequency groups comprise four frequencies from the various keys present on the telephone keypad; two different frequencies, one from the high frequency group and another from the low frequency group are used to produce a DTMF signal to represent the pressed key.
The amplitudes of the two sine waves should be such that
(0.7 < (A/B) < 0.9)V ——–>(2)
The frequencies are chosen such that they are not the harmonics of each other. The frequencies associated with various keys on the keypad are shown in figure (A).
When you send these DTMF signals to the telephone exchange through cables, the servers in the telephone exchange identifies these signals and makes the connection to the person you are calling.
Fig (A): The row and column frequencies
When you press the digit 5 in the keypad it generates a resultant tone signal which is made up of frequencies 770Hz and 1336Hz. Pressing digit 8 will produce the tone taken from tones 852Hz and 1336Hz. In both the cases, the column frequency 1336 Hz is the same. These signals are digital signals which are symmetrical with the sinusoidal wave.
Figure (B): A Typical frequency DTMF signal
Along with these DTMF generator in our telephone set provides a set of special purpose groups of tones, which is normally not used in our keypad. These tones are identified as ‘A’, ‘B’, ‘C’, ‘D’. These frequencies have the same column frequency but uses row frequencies given in the table in figure (A). These tones are used for communication signaling.
Figure (C): The frequency table
Due to its accuracy and uniqueness, these DTMF signals are used in controlling systems using telephones. By using some DTMF generating IC’s (UM91214, UM91214, etc) we can generate DTMF tones without depending on the telephone set.
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Sir,
I m interested in doing this project so can u plz send me all the details like circuit diagram, component used ,description and block diagram.Hoping for your reply as early as possible.
Thank you
sir,
i am interested in doing this project so can u please send me all the details like circuit diagram,component used and block diagram.waiting for your reply.
Thank You
sir,
I am interested in this project. can you send me the details please.
Thank you
I m interested in doing this project so can u plz send me all the details like circuit diagram, component used ,description and block diagram.Hoping for your reply as early as possible.
Thank you
I m interested in doing this project so can u plz send me all the details like circuit diagram, component used ,description and block diagram.Hoping for your reply as early as possible.
Thank you
I m interested in doing this project so can u plz send me all the details like circuit diagram, component used ,description and block diagram.Hoping for your reply as early as possible.
Thank you
Can u plz send me detail of d project with ckt diagram as soo as possible
can u plz tell me further addition in dis project ……i need to hav bigger project so i want to hav additon in it
sir plz send d block diagram of device control using mobile not by telephone
please send me the complete details with the block diagrames i am highly intrested.
please send me also the complete details of this system please.. i want to do this for our final project in school.. please send to my email giodale_18@yahoo.com thank you very much……
By using this project i want to construct the personally branched telephone exchange (PBEX) .SO PLEASE PROVIDE further information about this project circuit diagram and coding as soon as possible on my mail.iwill be very thankful to you.
Thank you for a very informative writeup. in my experience things are slighly more complicated than you make them seem. time will tell, but the problem is I do not have enough time. it is good to know we are not alone in the struggle. but you might want to reconsider some fragments in your post. after all, if it can do all that, why do we even need the rest anylonger? just a bit. take care
plz send me the project code…..
ur project is awesome still i need more information about it pls send the code also…..
please send me more detail am very interested
in this project
u r project is very intresting …i would like to do this ….sir plz send the entire controlling circuit description to my mail..plzzzzzz
kindly send me the complete information of this project using microcontroller 89C51 including circuit diagram and coding.please send me on the above mentioned email as soon as possible. Thanking you I remain
kindly send me complete detail including schemetic .
Nice project. Am gonna try it out.
sir,
I m interested in doing this project so can u plz send me all the details like circuit diagram, component used ,description and block diagram.Hoping for your reply as early as possible.
Thank you
PLS SEND ME THE CODING
sir can u send the the circuitdiagram and more details about project
sir,
I m interested in doing this project so can u plz send me all the details like circuit diagram
your project is very good. but i don’t like that. so never repeat it again.
.
Hi
I need the ful detail of project(Home appliance controller using DTMF) like circuit diagram, componont list ,discription,blockdiagram,equilanant ICs list that used in this project.
pls send me all the details 2 my is as soon as u can
i will be highly obliged
thanks in advance
its very important
pls send the details as soon as u can.
pls send the compltete ckt diagram using ic89c51,ic8870,ic uln2003,ic7806,regulatorls,relays and mobile phone connector
thanx
hello!
i want the fully detail of this project like circuit diagram, component,discription,blockdiagram,equilanant ICs list that used in this project and coding.
please……
i m very thankful to you…
sir,pls give full circuit diagram for using my prjct
sir pls give the code for this project
pls send the code for this project in my mail pls pls……..
salaam namasthe, what is the specification of the pcb to be used. pls help. thanks in advance
sir can i have the program code for the microcontroller at89s52 plss…..
sir, i have taken this up as my b.e project.
i am not using a cellphone as a dtmf input.. instead, i plan to use the dtmf encoder ic um91214.. but the problem is that the cost of this ic is around 1100rs which is not quite affordable for me.. so can you suggest any other affordable optional dtmf encoder ic..?
waiting for your reply..!
hello.. i m luking forward to make a project on DTMF based device control system for my final year.. kindly help me by providing d complete detailed description circuit diagram nd code of d project.. i shall b highly thankful to u..
Ranjith, Can you write to my email eewire3@gmail.com the contact details of the publisher of electrofriends.com
I need this for business purpose.
No contact link found on the home page!
Thanks
hey this is an interesting for my senior project can you send me the detail circuit diagram,coding etc…
pls .thank you
I m interested in doing this project so can u plz send me all the details like circuit diagram, component used ,description and block diagram.Hoping for your reply as early as possible.SIR kindly send me the code using at89c52…!!!!
sir, i am interested in doing this project so plz can u send me all the details like circuit diagram,component used and description and block diagram.hoping for reply as possible.
to interressado no projeto peco os diagrama e descrição completa
i am intrested in this project……..plz send me the details of this project
I m interested in doing this project so can u plz send me all the details like circuit diagram, component used ,description and block diagram.Hoping for your reply as early as possible.
Thank you
Im intrested in this project .
plz send me details.
thank you.
Wow….
I am interested to do this project for my home’s devices control so plz send me all details of this project with list all require components, circuit diagram, and details about how to do it…
I hope that you will send me all this detail earlier…
Thank you so much…
i want to make it, so plz send me all detail regarding this project.
I read all about this project and i like it so much, so can u plz send me all the details like circuit diagram, component used ,description and block diagram.Hoping for your reply as early as possible.
Thank you
hi i am using 89c2051 in this project which controls 8 relays and the controlling keys are 11,21—-81 to turn 1-8 relays and 10-80 to turn off.pls send me the program code for this as soon as possible.
sir,
can u send me the project to my mail id ovsureshbabu@gmail.com plz
hi, really very interesting project,please can you send me the full details of it,even every small detail,to work in one shot, my mail is vipinbali2010@gmail.com
thanks
vipin