MOBILE PHONE CONTROLLED ELECTRICAL APPLIANCES
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.
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 DTMFtechnology.
§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 shouldbe 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.
Video :Working of Mobile Controlled Appliances
TRY IT
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