Categories
Audio
Amplifiers, Audio Filters, Beeper & Buzzer, Equalizers, Intercom Circuits, Microphone Circuits, Mixers, Musical Circuits, Preamplifiers, Stereo Circuits, Tone-Balance, Ultrasonic Circuits, Vacuum Tubes, ...
|
Automations
|
Automotive
|
Computer
|
Converters
|
Digital
|
Inside Circuits |
Light-Laser-LED
|
Meter/Counter
|
Microcontrollers
|
Oscillators
Astable, Audio, Colpitts, Crystal, Hartley, Monostable Circuits, Pierce, RF, Sine wave, Square wave, Volt controlled, Wein Bridge, ...
|
Other Circuits
Buffer Circuits, Demodulators, Doorbell Circuits, Game Circuits, H-Bridge Circuits, Keypad Circuits, Model Circuits, Mosfet Circuits, Radar Circuits, Sequencer, Switch Circuits, Triac Circuits, ...
|
Power Supplies
|
RF
AM Circuits, Amplifiers, Antennas, FM Circuits, FM Transmitters, GPS Circuits, PLL Circuits, Receivers, Transceiver Circuits, Transmitters, UHF Circuits, VHF Circuits, ...
|
Security
|
Sensors/Detectors
Air-Gas, Hall Effect, Human, Light, Liquid, Magnetic circuits, Medical, Metal Detector circuits, Optical, RF & Radiation, Various Circuits, Voltage, ...
|
Software
|
Telephone
|
Video
|
|
Radio Remote Control using DTMF
Here is a circuit of a remote control unit which makes use of the radio frequency signals to control various electrical appliances. This remote control unit has 4 channels which can be easily extended to 12. This circuit differs from similar circuits in view of its simplicity and a totally different concept of generating the control signals. Usually remote control circuits make use of infrared light to transmit control signals. Their use is thus limited to a very confined area and line-of-sight. However, this circuit makes use of radio frequency to transmit the control signals and hence it can be used for control from almost anywhere in the house. Here we make use of DTMF (dual-tone multi frequency) signals (used in telephones to dial the digits) as the control codes. The DTMF tones are used for frequency modulation of the carrier. At the receiver unit, these frequency modulated signals are intercepted to obtain DTMF tones at the speaker terminals.
|
|