Indian Institute of Technology Hyderabad MOBILE CONTROLLED HOME APPLIANCES KOLLIPARA RITHWIK(ee12b1042) ALURI SAVIT VARCHASVI(es12b1017) VEMURU KALI CHARAN(cs12b1044)

INTRODUCTION  What had been thought impossible at one time was achieved by man.  As technology advanced man was able to control everything from one place.  Controlling electrical appliances with mobile is one of the examples.  This makes the use of DTMF(Dual Tone Multi Frequency) technique.  The DTMF Decoder circuit is made using M8870 Decoder IC.  Just connect your cell phone headset (headphone) jack to the mobile phone and then mobile control electrical appliances and electrical equipment via DTMF key pad of your cell phone.

REQUIREMENTS  Regulated power supply  DTMF decoder IC (M-8870)  Resistors (100Ω; 100kΩ; 70kΩ; 390kΩ)  Capacitors (0.1µFx 2)  Crystal oscillator ( MHz)  IC 7474 D flip flop  BC547 Transistor  6 V Relay

CIRCUIT DIAGRAM

WORKING  The project uses M-8870 DTMF decoder IC which decodes tone generated by the keypad of cell phone.  When we press keys in our cell Phone when call is in progress, the other person will hear some tones with respect to keys pressed. These tones are based on the DTMF technology.  Data is transmitted in terms of pair 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.  Cut the microphone wire and we will see 4 wires. Among these wires we need only 2 wires Ground and Right.  Take the right wire and connect it as input to the decoder circuit. Ground of jack 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 as Q1, Q2, Q3, and Q4.

 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 reset 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 * keys, the DTMF decoder IC generates a high pulse which acts as a clock to our flip flop and sets the output flip lop 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 connected at the normally open terminal of relay circuit

APPLICATIONS This system can be used in industrial applications. This system can be employed in houses,where people often forget to switch off electrical appliances This system can be used to control AC’s to set the room temperature when we are outside We can extend this circuit to control many electrical devices with some modifications using 4 x16 decoder IC.

ADVANTAGES Quick response is achieved. Construction is easy. Easy to maintain and repair. Comparatively the operation cost is less. Design is efficient and low cost. Power consumption is low. Controlling electrical devices wirelessly Saves electricity (when we forget to switch off and go out). We can control appliances from any place round the globe. No coding is required.

DISADVANTAGES This system is not capable of displaying the feed back status of the devices being operated. This system needs a cell phone to be placed in circuit. Any one who knows the phone number and code can control our electrical appliances Number of electrical appliances that can be controlled by this circit is limited Source