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

DTMF+Cell+Phone+controlled+home+appliances+engineering+project+circuit+diagram DTMF Cell Phone controlled Home appliances  Engineering automation project
                                                      (Click on the image for enlarged view)

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.
DTMF+Cell+Phone+controlled+home+appliances+engineering+project+2+headset+pin+and+wires DTMF Cell Phone controlled Home appliances  Engineering automation project
  • 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 DTMF Cell Phone controlled Home appliances  Engineering automation project

  • 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.

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

54 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!

    WITH MICROCONTROLLER YOU CAN SET PASSWORDS… CAN SET 10000000 COMMANDS AND MANY OTHER THINGS! THE SOURCE CODE IS JUST SIMPLY … YOU HAVE TO USE “GET HIGH” AND GET LOW

  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 :D 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……

  12. HI SIR I WOULD LIKE TO DO THE MINIPROJECT IN MOBILE CONTROLLING HOME APPLIANCES WITHOUT USING HOME MICROCONTROLLER . IS THERE ANY DISTANCE PROBLEM WHILE CONTROLING THE DEVICES SIR??

  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.

    Regards

    A.Nageshh

  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.
    Thanx

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