DTMF Cell Phone controlled Home appliances- Engineering automation project

Do you think that you can control your home and office electrical appliances using your cell phone? Yes.! you can… Here is a simple home controls home automation electronic mini project circuit diagram for engineering students, to control any electrical appliances using mobile phone without using a microcontroller. This circuit makes use of DTMF (Dual Tone Multi Frequency) technique. We have already posted on What is DTMF and DTMF decoder circuit using M8870 decoder IC.

This home appliances control or home automation project also uses the same DTMF decoder circuit section with little modifications to control home and office electrical appliances. Just connect your cell phone headset (headphone) jack to the mobile phone and then mobile will control electrical appliances and electrical equipment through the DTMF key pad of your cell phone. Here for demonstrating, we are controlling an electrical bulb using this circuit project but you can extend this circuit to control many electrical devices with some modifications using 4×16 decoder IC.

Microcontroller Project: Home appliances controlling using mobile phone circuit

Circuit diagram of mobile controlled home appliances

(Click on the image for enlarged view)
DTM Cell phone controlled appliances circuit

Components required for home automation

  1. Regulated power supply
  2. DTMF decoder IC (M-8870)
  3. Resistors (100Ω; 100kΩ; 70kΩ; 390kΩ)
  4. Capacitors (0.1µFx 2)
  5. Crystal oscillator (3.579545MHz)
  6. IC 7474 D flip flop
  7. BC547 Transistor
  8. 6V relay

Working of this home automation electronic project

  • Our project uses M-8870 DTMF decoder IC which decodes tone generated by the keypad of cell phone.
  • When you press any key on your mobile phone while call is in progress, the other person will hear some tones corresponding to the keys pressed. These tones are based on the DTMF (Dual Tone Multi Frequency) technology.
  • Data is transmitted as pairs of tones. The receiver detects the valid frequency pair and gives the appropriate BCD code as the output of the DTMF decoder IC.
  • DTMF signal can be tapped directly from the microphone pin of cell phone device.
  • See the figure below. Cut the microphone wire and you will be able to see 4 wires. Among these wires you need only 2 wires- Ground and Right as shown in figure.

  • Select the right wire and connect it as the DTMF input to the decoder circuit. Ground should be connected to common ground of our circuit.
  • The signals from the microphone wire are processed by the DTMF decoder IC which generates the equivalent binary sequence as a parallel output of Q1, Q2, Q3, and Q4.

Table showing DTMF Low and High frequency tones and decoded output

DTMF frequency output table

  • The output Q4 from the DTMF decoder IC is fed to the clock input of IC 7474 D flip flop which acts as a buffer to the output from M8870 DTMF decoder IC.
  • IC7474 is configured as Toggling mode, that is if it gets a clock pulse the output of this IC (Pin 5) sets to high and further clock pulse resets back the IC. (The outputs toggle whenever a key is pressed).
  • When we press and release any of the keys among 1, 3, 5, 7, 9 and *, the DTMF decoder IC generates a high pulse which acts as a clock to our flip flop and sets the output flip flop to high.
  • The output of flip flop is connected to the relay driver circuit via 100Ω resistor; this output energizes the relay coil through BC547 transistor and turns ON the bulb that is connected at the normally open terminal of relay circuit.

Probe further: Transistor inductive load driver circuit with animation

Video Demonstration of DTMF Cell Phone controlled Home appliances

Many of our readers request for video demonstrations for the circuits, but sadly due to time limitations we aren’t able to do that. However there are some of our fellow electronics lovers who makes it possible and shares it with rest of us. Kennethy who is from Tanzania is one of such talents, a big thumbs up for Kennethy for his efforts.

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Pin out of M8870 DTMF decoder, 7474 flip flop IC & BC547

146 thoughts on “DTMF Cell Phone controlled Home appliances- Engineering automation project

  1. mobile phone while call is in progress, the other person will hear some tones corresponding to the keys pressed. These tones are based on the DTMF (Dual Tone Multi Frequency) technology.
    what is the exact meaning of this????do we need any person at the receiver end???call in progress means sm1 has to pick the call???please clearify

    • Hi Abhishek,

      That means in mobile phones DTMF tones can be heard only when the receiver end has been attended. For this the phone should be in automatic answering mode so that the device can be controlled.

  2. sir,
    i made the dtmf decoder and the ckt. does not work in the flip flop area. by pressing the key i got the Q1 output but corresponding relay is not operating. i checked the relay and transistor but it’s not working.

    • Hey Gomathi,
      Power of the bulb depends on the current handling capacity of relay. Ampere specification can be found on the relay.

  3. Hai I am btech student I selected this topic as my miniproject .So need a detailed informatiin about ira working.Is is possible to control more than one load.how is all these loads switched on and off

    • Hi Hari,
      Really sorry for the delayed reply. The detailed information regarding the circuit is give in the post itself. More more you may please refer data sheets of those ICs. It is possible to control more than 1 load by simply adding more 7474 flip-flop ICs at the output of M8870 IC, which having Q1 to Q4 outputs. It means you can control maximum of 4 loads.

  4. i use ic 555 in mono stable mode instead of 74ls74,but it is not working,and when i call the phone and press the keys nothing is happening..pllzzzzzzz help..admin or anyone,i stuck in bw of the project.

    • Hi Salma,
      The section after DTMF decoder IC (M-8870) is a Bi-stable circuit, it can’t be a 555 monostable. Even though there is modifications to make 555 works as Bi-Stable. Please use 7474 as it could be more easy.

  5. Sir,please tell me the working reading of the relay used and what kind of relay it is means that the relay whether is DC or AC and please mention the specification and the pin out diagram for the same so that it is easy to make the circuit as per circuit diagram.Also I want to know about the DTMF input used in this circuit and the bulb specification.

  6. i build this project and it’s work nice! i’m a engineer and my opinion is that this schematic it’s so simply and so correctly that you can’t say “no working” if you are build the project like in the schematic draw. don;t try to simulate the project because you have to “build” the tones that the mt8870 will receive in “dtmf in”. if you don’t find mt8870 try it with kt3710 ( if i remember exactly)

  7. i can modify and do a better one with a microcontroller. ! who is interesed replay here and i will build the source code and the new schema!

    • Hi Allecs,
      We appreciate your skills that you could design with MCU. Is it possible to send the circuit to us with all required details? So we will publish here. That will be useful for other Electronics Geeks. Thanks

  8. and to explain all this project : you have 2 phones. ! the first is the “caller , the king” and the second is the “receiver , the slave” so … you call from king to slave. you have to set the slave phone to “answear automaticaly when is called”. the slave is answearing automaticaly, so from the time that slave answeared you can controll the “relay” for turning on the lamp with the “caller, the king” by pressing a key . so if you want to turn on the lamp at home in EUROPE and you are in SUA … just call from king to slave, press a key … and the light is turned on!


    • Hey allecs, using the microcontroller we will have to still work the king-slave concept with 2 phones itself right? If not can u explain it please?

  9. for people who build the project… and didn’t work…:

    you have to add Vdd(pin no.14) and GND(pin no.7) for FLIP FLOP IC … in the schematic is missing this. i will replay soon for people who want to try the project with a MCU.

  10. today i build again this project and i earn a profit of “10 $ ” =)) for it 😀 a friend like this and he want to open the water valve for grass irigation by a simply “call” :)) i didn’t use the flip flop… you can just wiring Q1 from dtmf to the “B” of the BC547 , “E” connected to ground and to gnd MT8870, and the “C” to relay. but …. when you press a key the relay will remain BLOCK TO HIS NEW POSITION…. it won’t go back to NO until you press again another key. have a nice day :))

  11. hi
    we are currently persuing this project for our final year project and got stuck at one point. we are unable to decide the wiring connection of the earphone. there are four wires- 1. green 2. dark green 3. brown 4. red……..which amongst this is the right and ground wire…….it will also be helpfull if u provide more detailed description about the earphone connection……


  13. Dear Sir,
    The project is very good, but I have one doubt. When we call the mobile connected to the circuit, how will the call mature ie when we use head phone in mobile and when there is an in coming call we have to press button to accept the call or to be connected to that phone, how this will happen here.



  14. Sir i need a cell phone controlled on-off switch circuit. This switch circuit must be missed call based.
    I mean to say that 1st miss call use to turn ON the circuit and then 2nd misscall use to turn OFF the circuit.
    Sir is it possible to built this type of circuit? Plz help me.
    And plz suggest me this type of ckt.

  15. HI
    This a very nice project and i wish with your permission to design this as my final year project. Please how do i contact you for guidance as i build this circuit to handle more loads. thank you

  16. Sir,
    I want to make project for getting information from pressurized tank.
    In mobile we can get information when pressure in tank reduces and or increses from specified set pressure.
    We can make arrangement to operate limit switch.

  17. sir, pls help me. i want to do this kind of project in my school requirments. pls tell what materials should i use. thanks for response

  18. Helow sir,
    Can you please tell me what signal does the ic mt 8870 recive from the phone..?is it voltage/current or is it analog frequence from DTMF ?(mechanism which is done from reciver mobile to the ic)
    And if i am away from the applience /home how will i know the light is ON or OFF is there any feedback or i just assume its ON…?

  19. Sir plz helppp…..I have made this project bu its nt workin …plz upload a video of the same as early as possible
    Thankin u in advance

  20. can i ask the video for this project?
    i tried this project but it didnt work. i dont know why.
    maybe because of the microphone pin. pls tell us how to know if its the right and the ground wire. thanks

  21. Sir, i have made this home automation ckt given here…….but its not working…my relay operates by the action of battery only but not by the cell phone….when i called to the cell phone attached to my ckt n press any keys from 1,3,5,7,9,* nothing is happening…..plz solve my problem sir….please suggest me some way to troubleshoot the ckt problem…….n please sir reply as soon as possible…..

  22. How to determine which number switches on which relay and which number switches off which relay?
    Please reply thanks.

    • there are 4 outputs as you can see from DTMF table from (Q1 TO Q4) SO each output has ts own activated and deactivate logical/digital numbers from remote phone.
      example from Q1
      1-7 are off or zero and 8 – # are on/ones so each output works independently

  23. hi,
    I want to know which number is set for which relay in since there are 4 outputs and how to switch them off individually,
    and what if i am at home and want to operate manually.

  24. hello sir
    am so grateful for this project i have done it and i have successful archive my goals.it is not hard at all and very accurate.project
    thank you again sir.

  25. Is it possible to transmit the DTMF signals without calling?? To reduce working cost. I have already done a device by using the call method, but trying for some other way. I think there is an app to produce the tones, but i am not sure

  26. Hi Jaseem,
    I want to control 30 relays ie independent switch on/ off using your ckt . send me a diagram to my mail id .
    I want the circuit to work with tel line connected and also without tel line ie by self generating dtmf circuit.

    Regards Sambath kumar.

  27. Yes you can but you will have to use voltge regulator 7805..for regulate volatge from 9v to 5v becouse both ic (mt8870 and 7474) use input voltage of 5v…and from what i have observe old phone are the best to use but try to find supportng auto cell.

  28. the whole concept of this project is to eliminate all manual stuffs…thats why you make the call its pick itself you turn on/off your appliance without you/anyone been there….but of course you can still receive input even if you attend manually

  29. How to personal use the DTMF switch .If other phone signal disturb this circut.please give me details suggestion .I want switch control myself.

    • the switch depends on the receiving signal and this signals received are dedicated channels(condition)…i.e when you make a call then other hand peek means they are connected and any conversation can continue but technically this means the switch is connects to the caller phone means he/she can switch/control the appliance(s) since the receiver phone is connected to the circuit..so means if u don’t want anyone not to disturb this circuit means the receiver phone must not receiver any other calls from other phone other than yours because anyone who can make a call can also switch the appliance unless you use micro-controller for condition the circuit.

      • Hello Kenny,
        It’s great to see you here 🙂 . We are very much impressed by your passion and the dedication you put to help others too. We had sent you an email, kindly check your inbox and do reply.

  30. Hi…… i want to a new member in this and i want to make a project based on DTMF. Could u plz help me if i got a problem?Thank u very much!

    • Hi Ijaz
      If you want to use 5V/15A relay, same circuit is enough.
      To connect 12V/15A relay, connect relay top connection to 12V from 5V and use same ground connection if you are using different power supply.

  31. Do i use AND gates in the output of M8870 , So that we can use all the inputs from my mobile Button (1 to #) to 12 different outputs ,

  32. Sir I have done a project based on your circuit diagram for mobile controlled home applience.But it doesn’t work while calling from another phone.What should I do?? Could you please help

  33. hi sir how are u

    i want to tell u i already made this project and its working so good
    but the problem is this
    the dtmf 8870 ic not working correctly with every mobile just working few mobiles

    can u tell me about the accurate value of R1 and R2 which connected 8870 ic pin of 2 and 3

    just tell me accurate value

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