Cell Phone Controlled Home Appliance circuit

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 sho
Cell Phone Controlled Home Appliance circuit - schematic

wn 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. 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...

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