Circuit Description:
Ever Imagined controlling your home appliances using your cell phone. You can find a lot of circuits for this application. But they make use of Telephone. I modified the circuit and redesigned it to make it compatible with normal cell phone headphone. Just connect the your phone headphone jack to the phone and the connections to the circuit as shown in the circuit. The relays are connected using the resistor and transistor. Use ULN2803 to reduce the circuit size and increase the performance. The connections from the output of flip-flops has to be given to the inputs of the buffer and relays has to be connected to the buffer.
Normally the tip of the headset is connected to the circuit to the 0.1uF capacitor as shown in the circuit diagram. The ground pin of headphone is connected to the ground of the circuit.
Circuit Diagram:
Operation:
When you press keys in your Phone, the other person will hear some tones with respect to keys pressed. This tones are based on the DTMF technology. Data is transmitted in terms of pair of tones. The receiver detects the valid pair and gives the appropriate BCD code as the output of the DTMF decoder IC.
The output of the DTMF IC is given to the 4x16 decoder IC. We have 12 signals possible because we have 12 keys (including * and #) in mobile keypad. The decoder are outputs are then given to D flip-flops. The outputs toggle whenever a key is pressed.
In DTMF there are 16 distinct tones. Each tone is the sum of two frequencies: one from a low and one from a high frequency group. There are four different frequencies in each group.
Your phone only uses 12 of the possible 16 tones. If you look at your phone, there are only 4 rows (R1, R2, R3 and R4) and 3 columns (C1, C2 and C3). The rows and columns select frequencies from the low and high frequency group respectively. The exact value of the frequencies are listed in Table 3 below:
Thus to decipher what tone frequency is associated with a particular key, look at your phone again. Each key is specified by its row and column locations. For example the "2" key is row 0 (R1) and column 1 (C2). Thus using the above table, "2" has a frequency of 770 + 1336 = 2106 Hz The "9" is row 2 (R3) and column 2 (C3) and has a frequency of 852 + 1477 = 2329 Hz.
The following graph is a captured screen from an oscilloscope. It is a plot of the tone frequency for the "1" key:
You can see that the DTMF generated signal is very distinct and clear. The horizontal axis is in samples. The frequency of the tone is about 1900 Hz - close to the 1906 Hz predicted by Table 3 (697+1209).
Your phone only uses 12 of the possible 16 tones. If you look at your phone, there are only 4 rows (R1, R2, R3 and R4) and 3 columns (C1, C2 and C3). The rows and columns select frequencies from the low and high frequency group respectively. The exact value of the frequencies are listed in Table 3 below:
| LOW-FREQUENCIES | |
| ROW # | FREQUENCY (HZ) |
| R1: ROW 0 | 697 |
| R2: ROW 1 | 770 |
| R3: ROW 2 | 852 |
| R4: ROW 3 | 941 |
| HIGH-FREQUENCIES | |
| COL # | FREQUENCY (HZ) |
| C1: COL 0 | 1209 |
| C2: COL 1 | 1336 |
| C3: COL 2 | 1477 |
| C4: COL 3 | 1633 |
| C4 not used in phones |
Thus to decipher what tone frequency is associated with a particular key, look at your phone again. Each key is specified by its row and column locations. For example the "2" key is row 0 (R1) and column 1 (C2). Thus using the above table, "2" has a frequency of 770 + 1336 = 2106 Hz The "9" is row 2 (R3) and column 2 (C3) and has a frequency of 852 + 1477 = 2329 Hz.
The following graph is a captured screen from an oscilloscope. It is a plot of the tone frequency for the "1" key:
You can see that the DTMF generated signal is very distinct and clear. The horizontal axis is in samples. The frequency of the tone is about 1900 Hz - close to the 1906 Hz predicted by Table 3 (697+1209).
Arifuddin Sheik
31 comments:
Hello Arif,
Avinash (from eXtreme electronics) here ...
From my Records I found that you have bought an xBoard MINI v2.0 from us. Can you showcase some of your project/experiments with it? I will pay you for that !
Definitely I am going to do that. I started posting my projects from today. I was busy with exams and holidays. I am back to my work now.
hi,arif this is srinivas ,the schematic here is a very nice one ,so as a hobbyist i deciced to make one for my home appliances,bt there is a doubt in my mind,cud u plz tell me where shall i connect the pins o2 to o7 ,and N/U as well,?
hello,
may i know where the appliances has to be connected....is it from output pin of CD 4049 IC?
how can we ground the headset connections.....am unable to get that...
can u send me a complete component fitted pcb with instruction it willbe a very help full project for me.
Hello Arif,
I need to buy a completed product for some farmers in my village. I want mobile to control there water pumps. Can suggest me from where I can purchase plenty of such gadgets which will work reliably.
Home Appliances are the elecrical or mechanical devices which have been used to perform various household functions such as cooking and cleaning effectively.
hey nice work
i want to make the same project can you provide me the necessary details.
my emailid is
yogeshtayal123@yahoo.com
hey nice work
i want to make the same project can you provide me the necessary details
Wow, Fantastic article, it’s so helpful to me, and your blog is very good,
Upright Freezers
This is a good common sense Blog. Very helpful to one who is just finding the resources about this part. It will certainly help educate me.Online electronics store
Hi,I like to do this one as my final year project.But i am confused about the connections for headphones and cellphones.You said that the tip of the headphone is connected to the Capacitor and the ground is grounded.Then where is the cellphone connected?Please clear my doubt.
heyy i m geetika,,,,
nice project ,,,i want to make the same...
can u send me the clear circuit diagram and components required 4 this projects. and also a completely fitted picture of this project
nice project ,,,i want to make the same...
can u send me the clear circuit diagram and components required 4 this projects.
this is my mail id:savee197@gmail.com
nice project ,,,i want to make the same...
can u send me the clear circuit diagram and components required 4 this projects.
this is my mail id:savee197@gmail.com
pls send me clear diagram of this project & rating of the all component used here pls pls......my email is
yadavshiv666@gmail.com
hello arif
my name is daksh
iam a 3rd yr student
i hv thee block diagram represenation........but i dotn know exactly how to makes its circuit
can u please guide me to th point that how to find correct values of resistore and other passive divices....................
how we get to know that how much of current v need to have on particular node..........???
Hello Arif,
Anirudh Som (from GITAM univ)here
how do i connect my electrical appliances to the circuit.... my mail id is anirudhsom3000@gmail.com
myself sangram
i want to do this project so send me clear ckt dig mail id sangramak@gmail.com
plz do fast
Asallamwalekum ARIF ,
This is RIZWAN KHAN {pursuing B.E.(Electrical & electronics)}. DTMF for cell phone cantrolled is brillient and a new softwr has been uploaded in the cell phone yet to launch to cantrol the lights from anywhere in the world. But we will be in work to have some more inovative experiment in this field. All the very best to you n your company . ALLAH HAFIZ & FACE WELL
Really Helpful Post
Thank you very much.......
feel free to surf Electronics Projects and Circuits
Good Work.
Hello sir, i m vikas. I want to make same project (mobile controlle home appliances). Plz email me circuit layout and source code on vikasec31106@gmail.com
helloz, i am himanshu i am doing btech in electronics and instrumentation. i want to make the same project in the last sem. so kindly send me the clear ckt diagram, components used, component fitted pcb,that will help me in making my project. my mail id is.
himanshukandpal16@gmail.com
This is the kind of products which people should buy. Amazing work of creativity.
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useful information on topics that plenty are interested on for this wonderful post.Admiring the time and effort you put into your b!.. electrical appliances
This is my first time i visit here and I found so many interesting stuff in your blog especially it's discussion, thank you. appliance repair technicians
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