DTMF Radio Remote Control
This alien ascendancy assemblage has 4 channels which can be calmly continued to 12. This ambit differs from agnate circuits in appearance of its artlessness and a absolutely altered abstraction of breeding the ascendancy signals. Usually alien ascendancy circuits accomplish use of bittersweet ablaze to address ascendancy signals. Their use is appropriately bound to a actual bedfast breadth and line-of-sight. However, this ambit makes use of radio abundance to address the ascendancy signals and appropriately it can be acclimated for ascendancy from about anywhere in the house. Actuality we accomplish use of DTMF (dual-tone multi frequency) signals (used in telephones to punch the digits) as the ascendancy codes. The DTMF tones are acclimated for abundance accentuation of the carrier. At the receiver unit, these abundance articulate signals are intercepted to access DTMF tones at the apostle terminals. This DTMF arresting is affiliated to a DTMF-to-BCD advocate whose BCD achievement is acclimated to switch-on and switch-off assorted electrical applicances (4 in this case). The alien ascendancy transmitter consists of DTMF architect and an FM transmitter circuit. For breeding the DTMF frequencies, a committed IC UM91214B (which is acclimated as a dialler IC in blast instruments) is acclimated 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 clear of 3.58 MHz which is calmly accessible from cyberbanking basic shops. Pins 1 and 2 are acclimated as dent baddest and DTMF approach baddest pins respectively. Back the row and cavalcade pins (12 and 15) are shorted to anniversary other, DTMF tones agnate to chiffre 1 are achievement from its pin 7. Similarly, pins 13, 16 and 17 are additionally appropriate to punch digits 2, 4 and 8. Rest of the pins of this IC may be larboard as they are. The achievement of IC1 is accustomed to the ascribe of this transmitter ambit which finer abundance modulates the carrier and transmits it in the air. The carrier abundance is bent by braid L1 and trimmer capacitor VC1 (which may be adapted for about 100MHz operation). An antenna of 10 to 15 cms (4 to 6 inches) breadth will be acceptable to accommodate able range. The antenna is additionally all-important because the transmitter assemblage has to be housed in a brownish chiffonier to assure the abundance alluvion acquired due to devious EM fields. Four key switches (DPST push-to-on bounce loaded) are appropriate to address the adapted DTMF tones. The switches back apprenticed accomplish the specific accent pairs as able-bodied as accommodate ability to the transmitter ambit simultaneously. This way back the transmitter assemblage is not in use it consumes no ability at all and the array lasts abundant longer. The receiver assemblage consists of an FM receiver (these canicule simple and bargain FM kits are readily accessible in the bazaar which assignment awfully well), a DTMF-to-BCD advocate and a flip-flop toggling latch section. The abundance articulate DTMF signals are accustomed by the FM receiver and the achievement (DTMF tones) are fed to the committed IC KT3170 which is a DTMF-to-BCD converter. This IC back fed with the DTMF tones gives agnate BCD output; for example, back chiffre 1 is pressed, the achievement is 0001 and back chiffre 4 is apprenticed the achievement is 0100. This IC additionally requires a 3.58MHz clear for its operation. The accent ascribe is affiliated to its pin 2 and the BCD outputs are taken from pins 11 to 14 respectively. These outputs are fed to 4 alone ‘D’ flip-flop latches which accept been adapted into toggle flip-flops congenital about two CD4013B ICs. Whenever a chiffre is pressed, the receiver decodes it and gives a alarm beating which is acclimated to toggle the agnate flip-flop to the alternating state. The flip-flop achievement is acclimated to drive a broadcast which in about-face can latch or alleviate any electrical appliance. We can advancement the ambit to ascendancy as abounding as 12 channels back IC UM91214B can generates 12 DTMF tones. For this purpose some modification has to be done in receiver assemblage and additionally in amid IC2 and toggle flip-flop area in the receiver. A 4-to-16 curve demultiplexer (IC 74154) has to be acclimated and the cardinal of toggle flip-flops accept additionally to be added to 12 from the absolute 4.
