In earlier days, our telephone systems were operated by manually in a telephone exchange room. The callers will pick up the phone and giving instruction to the operator to connect their destination line. The DTMF technology provides ultimate solutions for the telephone industries which is used to switch two lines automatically. The DTMF stands for ‘Dual Tone Multi-frequency’ which is one of the techniques for converting the analogue signal to digital using DTMF decoder. The DTMF decoder circuit mostly used in mobile communications system which recognizes the sequence of DTMF tones from the standard keypad of the mobile phone.
DTMF Decoder Application Circuit and Working Procedure
DTMF keypad is placed out on a 4 cross 4 matrices, in which each row represents low frequency, each column represents high frequency, with DTMF, each key passed on a phone generates two tones of the specific frequencies one tone is generated from a high frequency tones and low frequency tone. These tones are converted to digital form using DTMF decoder circuit. These codes are the address of the destination which is read and preceded by the computer that connects the caller to the destination. The DTMF decoder circuit used in many electronics projects for better connectivity to control the applications.
DTMF Decoder based Home Automation System and its Working Procedure
In previous days, the home applications are controlled by manually using switches. Now a day, many technologies are available to control home appliances. This project mainly discusses DTMF decoder circuit to control the home applications. The working procedure of this project is just like dialing a customer care number using DTMF technology by following automatic voice recorded instructions. It will ask to press 1,2 or any other number when you press number to your mobile one particular procedure is happening. This is called a DTMF technology. If any button is pressed on the mobile phone keypad, then it will generate two frequencies. These tones are called row are column frequencies. Normally row frequencies are low frequencies and column frequencies are high frequencies. These column frequencies are slightly louder than the row frequencies to compensate for the high-frequency roll off of voice audio systems.
The main objective of this project is to control the home applications like light, electric fan or some electronic gadgets by using DTMF techniques. DTMF encoder is present in mobile and the DTMF decoder circuit is present in the microcontroller. The mobile is connected at one end of the circuit with the help of the mobile phone jack. The mobile jack is consisting of two wires. The red wire is connected to the decoder IC and Black is grounded. When a button is pressed from mobile it generates a tone which is decoded by the decoder IC and it’s sent to the micro controller. The controller checks the inputs and delivers the respective outputs according to the code written on it.
Pin Architecture and Circuit Explanation of DTMF
The decoder IC is an electronics circuit which is consisting of an inbuilt op-amp and to separate low and high frequencies, the output of an operational amplifier is given to the pre-filters. And it passed though the code detector and frequency circuits. The tone which is generated from the mobile is sent through a capacitor and the resistor of the DTMF.
- pin1 is a non inverting pin, which is connected to the pin 4.
- Pin3 is the output of the operational amplifier, which is feedback to the pin 2.
- The pin 7 and pin 8 is connected to the crystal oscillator of both pins.
- Pin 15 is the data interconnection pin.
- The procedure of the signal from the frequency detection to digitalization, is done steering circuit that consists of resistor, capacitors, receiver and transmitter and etc.
- 11, 12 pins are output pins that are connected DTMF pins. Then DTMFis connected to relay.
- Relay output is connected pb0 and pb3 pins of microcontrollers.
- PD0, PD1 are output pins of controller, that are connected to the relays.
- Relay output is connected to the load.
Automatic Garage Door Opening System
The main goal of this project is to design an automatic door locking and unlocking system using a mobile phone over long distances. This method is very convenient as it reduces the energy to get down from the car to open/close the gate physically. Nowadays opening and closing of garage doors in the homes, hospitals and other places involves human work. With this proposed system, the opening and closing of a garage door can be achieved by using a mobile phone with the unique password entered through the keypad of the phone.
If any button is pressed to generate a respective tone on the user phone, the same tone will be heard at the other end of the cell attached to the circuit to operate the door. This tone is called ‘Dual Tone Multi Frequency’ (DTMF) tone. The received tone is processed by the 8051 microcontroller with the help of the DTMF decoder. If this decoded value (password entered by the user) matches with the stored password in the microcontroller, then the microcontroller initiates a mechanism to the door opening system through a motor driver.
Cell Phone Controlled Robotic Vehicle using DTMF Technology
The main aim of the project is to control a robot movement over long distance with a mobile phone. The proposed system uses a microcontroller of 8051 family to control the whole application. If a button is pressed to generate a corresponding tone in the user phone, the same tone can be heard at the receiver end of the cell attached to the robot, to operate the robot. This tone is called ‘Dual Tone Multi Frequency’ (DTMF) tone. The received tone is processed by the 8051 microcontroller with the help of the DTMF decoder. The microcontroller is preprogrammed to take the decision for any given input and output, wherein the motor drives the robot in forward and backward direction.
Display of Dialed Telephone Numbers on Seven Segment Display
The aim of this project is to provide better visibility by displaying the dialed telephone numbers on a seven-segment display using DTMF technology. In this project uses a microcontroller of the 8051 family and a rectified-power supply. In this project, a land phone is attached to the circuit through a DTMF decoder for developing the digital output.
10- numeric LED displays are connected to the microcontroller for displaying the numbers at the same time. If any button is pressed, it generates a corresponding tone on the land phone which is connected to the circuit. This tone is called ‘dual tone multi frequency’ (DTMF) tone. This tone is processed by the microcontroller with the help of the DTMF decoder. Then, the microcontroller delivers the same data to a set of parallel connected seven-segment displays.
The main goal of this project is to provide security to banks, homes, museums and other security intended places with an automatic dialing system capable of dialing a predefined telephone number whenever any unauthorized person tries to open the door to which it is attached. Nowadays, the crime rate is on the rise in the world and burglars are getting smarter; therefore, security system is very important for the places where security is intended. The proposed system is enhanced to provide security and to intimate the concerned authorities when unauthorized access happens to secured areas. This proposed system uses a microcontroller of the 8051 family, and a rectified-power supply.
In this system, the EEPROM is interfaced to the microcontroller to store the information. A matrix keypad attached to the microcontroller is used for entering the input data. A land phone is connected to the microcontroller through a DTMF encoder. A push button switch connected to the microcontroller is used for giving the inputs. If an authorized number is entered from the matrix keypad, then the controller sends that number to store it in an external EEPROM through the I2C bus. When someone tries to open the door forcefully, then the microcontroller gets an interrupt through a switch and automatically dials that number in the tone mode by DTMF technology, which is stored in the EEPROM. All the information is displayed on the LCD display as per the program.
Thus, this is all about what is dtmf decoder and dtmf decoder working with applications.We believe that, you have got a better idea about this concept.Furthermore, any queries regarding DTMF based projects, please visit www.edgefxkits.com