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The remote control transmitter consists of DTMF generator and an FM transmitter circuit. For generating the DTMF frequencies, a dedicated IC UM91214B (which is used as a dialler IC in telephone instruments) is used here. This IC requires 3 volts for its operation. This is provided by a simple zener diode voltage regulator which converts 9 volts into 3 volts for use by this IC. For its time base, it requires a quartz crystal of 3.58 MHz which is easily available from electronic component shops. Pins 1 and 2 are used as chip select and DTMF mode select pins respectively. When the row and column pins (12 and 15) are shorted to each other, DTMF tones corresponding to digit 1 are output from its pin 7. Similarly, pins 13, 16 and 17 are additionally required to dial digits 2, 4 and 8. Rest of the pins of this IC may be left as they are. The output of IC1 is given to the input of this transmitter circuit which effectively frequency modulates the carrier and transmits it in the air. The carrier frequency is determined by coil L1 and trimmer capacitor VC1 (which may be adjusted for around 100MHz operation). Complete Circuit Diagram click here
Tags : zener diode voltage regulator, fm transmitter circuit, coil l1, zener diode voltage, dtmf mode, radio remote control, quartz crystal, control transmitter, dtmf tones, telephone instruments, vc1, time base, simple zener, carrier frequency, electronic component
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February 6th, 2009 at 9:54 am
please i need information (lastest ) that you can lay your hands on on security doorlock
April 1st, 2009 at 2:58 pm
using FM transmitter and receiver you can control the electrical instrument