The DC motor control system is basically an embedded one. The main objective of this project to control DC motor & home appliances wirelessly and from any part of world. This requires a unique product. Now if we want a system to control this from any part of world then it is possible using technology DTMF. DC motor speed and direction control system with help of H Bridge IC.
During phone calling, if any button is pressed, a tone corresponding to the button pressed is heard at the other end of the call. This tone is called "Dual Tone Multiple-Frequency" (DTMF) tone. The Decoder decodes this DTMF tone with the help of the phone stacked sound jack. This decoded information send to the Microcontroller and appropriate operation performed.
DTMF is acronym for Dual Tone Multi Frequency. So, just think when we make call for customer care, they will ask you to press 1, 2 or any other number. When you press a number from your mobile, one particular action is happening. All this is because of DTMF. When a button is pressed in your mobile keypad, it will generate a tone of two frequencies. These tones are called row and column frequencies.
Generally, row frequencies are low frequencies and column frequencies are high frequencies. These frequencies for DTMF are chosen in such a way that they don’t have harmonic relation with the others, so that they will not produce same tones. The column frequencies are slightly louder than the row frequencies to compensate for the high-frequency roll off of voice audio systems.
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